Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

103 files changed, 9485 insertions, 0 deletions

diff --git a/devtools/client/aboutdebugging/src/actions/debug-targets.js b/devtools/client/aboutdebugging/src/actions/debug-targets.js
new file mode 100644
index 0000000000..33b2f1cbea
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/actions/debug-targets.js
@@ -0,0 +1,356 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs",
+  // AddonManager is a singleton, never create two instances of it.
+  { loadInDevToolsLoader: false }
+);
+const {
+  remoteClientManager,
+} = require("resource://devtools/client/shared/remote-debugging/remote-client-manager.js");
+
+const {
+  l10n,
+} = require("resource://devtools/client/aboutdebugging/src/modules/l10n.js");
+
+const {
+  isSupportedDebugTargetPane,
+} = require("resource://devtools/client/aboutdebugging/src/modules/debug-target-support.js");
+
+const {
+  openTemporaryExtension,
+} = require("resource://devtools/client/aboutdebugging/src/modules/extensions-helper.js");
+
+const {
+  getCurrentClient,
+  getCurrentRuntime,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js");
+
+const {
+  gDevTools,
+} = require("resource://devtools/client/framework/devtools.js");
+
+const {
+  DEBUG_TARGETS,
+  DEBUG_TARGET_PANE,
+  REQUEST_EXTENSIONS_FAILURE,
+  REQUEST_EXTENSIONS_START,
+  REQUEST_EXTENSIONS_SUCCESS,
+  REQUEST_PROCESSES_FAILURE,
+  REQUEST_PROCESSES_START,
+  REQUEST_PROCESSES_SUCCESS,
+  REQUEST_TABS_FAILURE,
+  REQUEST_TABS_START,
+  REQUEST_TABS_SUCCESS,
+  REQUEST_WORKERS_FAILURE,
+  REQUEST_WORKERS_START,
+  REQUEST_WORKERS_SUCCESS,
+  TEMPORARY_EXTENSION_INSTALL_FAILURE,
+  TEMPORARY_EXTENSION_INSTALL_START,
+  TEMPORARY_EXTENSION_INSTALL_SUCCESS,
+  TEMPORARY_EXTENSION_RELOAD_FAILURE,
+  TEMPORARY_EXTENSION_RELOAD_START,
+  TEMPORARY_EXTENSION_RELOAD_SUCCESS,
+  TERMINATE_EXTENSION_BGSCRIPT_FAILURE,
+  TERMINATE_EXTENSION_BGSCRIPT_SUCCESS,
+  TERMINATE_EXTENSION_BGSCRIPT_START,
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+
+function getTabForUrl(url) {
+  for (const navigator of Services.wm.getEnumerator("navigator:browser")) {
+    for (const browser of navigator.gBrowser.browsers) {
+      if (
+        browser.contentWindow &&
+        browser.contentWindow.location.href === url
+      ) {
+        return navigator.gBrowser.getTabForBrowser(browser);
+      }
+    }
+  }
+
+  return null;
+}
+
+function inspectDebugTarget(type, id) {
+  return async ({ dispatch, getState }) => {
+    const runtime = getCurrentRuntime(getState().runtimes);
+
+    if (
+      type == DEBUG_TARGETS.EXTENSION &&
+      runtime.id === RUNTIMES.THIS_FIREFOX
+    ) {
+      // Bug 1780912: To avoid UX issues when debugging local web extensions,
+      // we are opening the toolbox in an independant window.
+      // Whereas all others are opened in new tabs.
+      gDevTools.showToolboxForWebExtension(id);
+    } else {
+      const urlParams = {
+        type,
+      };
+      // Main process may not provide any ID.
+      if (id) {
+        urlParams.id = id;
+      }
+
+      if (runtime.id !== RUNTIMES.THIS_FIREFOX) {
+        urlParams.remoteId = remoteClientManager.getRemoteId(
+          runtime.id,
+          runtime.type
+        );
+      }
+
+      const url = `about:devtools-toolbox?${new window.URLSearchParams(
+        urlParams
+      )}`;
+
+      const existingTab = getTabForUrl(url);
+      if (existingTab) {
+        const navigator = existingTab.ownerGlobal;
+        navigator.gBrowser.selectedTab = existingTab;
+        navigator.focus();
+      } else {
+        window.open(url);
+      }
+    }
+
+    dispatch(
+      Actions.recordTelemetryEvent("inspect", {
+        target_type: type.toUpperCase(),
+        runtime_type: runtime.type,
+      })
+    );
+  };
+}
+
+function installTemporaryExtension() {
+  const message = l10n.getString(
+    "about-debugging-tmp-extension-install-message"
+  );
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: TEMPORARY_EXTENSION_INSTALL_START });
+    const file = await openTemporaryExtension(window, message);
+    try {
+      await AddonManager.installTemporaryAddon(file);
+      dispatch({ type: TEMPORARY_EXTENSION_INSTALL_SUCCESS });
+    } catch (e) {
+      dispatch({ type: TEMPORARY_EXTENSION_INSTALL_FAILURE, error: e });
+    }
+  };
+}
+
+function pushServiceWorker(id, registrationFront) {
+  return async ({ dispatch, getState }) => {
+    try {
+      // The push button is only available if canDebugServiceWorkers is true.
+      // With this configuration, `push` should always be called on the
+      // registration front, and not on the (service) WorkerTargetActor.
+      await registrationFront.push();
+    } catch (e) {
+      console.error(e);
+    }
+  };
+}
+
+function reloadTemporaryExtension(id) {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: TEMPORARY_EXTENSION_RELOAD_START, id });
+    const clientWrapper = getCurrentClient(getState().runtimes);
+
+    try {
+      const addonTargetFront = await clientWrapper.getAddon({ id });
+      await addonTargetFront.reload();
+      dispatch({ type: TEMPORARY_EXTENSION_RELOAD_SUCCESS, id });
+    } catch (e) {
+      const error = typeof e === "string" ? new Error(e) : e;
+      dispatch({ type: TEMPORARY_EXTENSION_RELOAD_FAILURE, id, error });
+    }
+  };
+}
+
+function removeTemporaryExtension(id) {
+  return async ({ getState }) => {
+    const clientWrapper = getCurrentClient(getState().runtimes);
+
+    try {
+      await clientWrapper.uninstallAddon({ id });
+    } catch (e) {
+      console.error(e);
+    }
+  };
+}
+
+function terminateExtensionBackgroundScript(id) {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: TERMINATE_EXTENSION_BGSCRIPT_START, id });
+    const clientWrapper = getCurrentClient(getState().runtimes);
+
+    try {
+      const addonTargetFront = await clientWrapper.getAddon({ id });
+      await addonTargetFront.terminateBackgroundScript();
+      dispatch({ type: TERMINATE_EXTENSION_BGSCRIPT_SUCCESS, id });
+    } catch (e) {
+      const error = typeof e === "string" ? new Error(e) : e;
+      dispatch({ type: TERMINATE_EXTENSION_BGSCRIPT_FAILURE, id, error });
+    }
+  };
+}
+
+function requestTabs() {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: REQUEST_TABS_START });
+
+    const runtime = getCurrentRuntime(getState().runtimes);
+    const clientWrapper = getCurrentClient(getState().runtimes);
+
+    try {
+      const isSupported = isSupportedDebugTargetPane(
+        runtime.runtimeDetails.info.type,
+        DEBUG_TARGET_PANE.TAB
+      );
+      const tabs = isSupported ? await clientWrapper.listTabs() : [];
+
+      // Fetch the favicon for all tabs.
+      await Promise.all(
+        tabs.map(descriptorFront => descriptorFront.retrieveFavicon())
+      );
+
+      dispatch({ type: REQUEST_TABS_SUCCESS, tabs });
+    } catch (e) {
+      dispatch({ type: REQUEST_TABS_FAILURE, error: e });
+    }
+  };
+}
+
+function requestExtensions() {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: REQUEST_EXTENSIONS_START });
+
+    const runtime = getCurrentRuntime(getState().runtimes);
+    const clientWrapper = getCurrentClient(getState().runtimes);
+
+    try {
+      const isIconDataURLRequired = runtime.type !== RUNTIMES.THIS_FIREFOX;
+      const addons = await clientWrapper.listAddons({
+        iconDataURL: isIconDataURLRequired,
+      });
+
+      const showHiddenAddons = getState().ui.showHiddenAddons;
+
+      // Filter out non-debuggable addons as well as hidden ones, unless the dedicated
+      // preference is set to true.
+      const extensions = addons.filter(
+        a => a.debuggable && (!a.hidden || showHiddenAddons)
+      );
+
+      const installedExtensions = extensions.filter(
+        e => !e.temporarilyInstalled
+      );
+      const temporaryExtensions = extensions.filter(
+        e => e.temporarilyInstalled
+      );
+
+      dispatch({
+        type: REQUEST_EXTENSIONS_SUCCESS,
+        installedExtensions,
+        temporaryExtensions,
+      });
+    } catch (e) {
+      dispatch({ type: REQUEST_EXTENSIONS_FAILURE, error: e });
+    }
+  };
+}
+
+function requestProcesses() {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: REQUEST_PROCESSES_START });
+
+    const clientWrapper = getCurrentClient(getState().runtimes);
+
+    try {
+      const mainProcessDescriptorFront = await clientWrapper.getMainProcess();
+      dispatch({
+        type: REQUEST_PROCESSES_SUCCESS,
+        mainProcess: {
+          id: 0,
+          processFront: mainProcessDescriptorFront,
+        },
+      });
+    } catch (e) {
+      dispatch({ type: REQUEST_PROCESSES_FAILURE, error: e });
+    }
+  };
+}
+
+function requestWorkers() {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: REQUEST_WORKERS_START });
+
+    const clientWrapper = getCurrentClient(getState().runtimes);
+
+    try {
+      const { otherWorkers, serviceWorkers, sharedWorkers } =
+        await clientWrapper.listWorkers();
+
+      for (const serviceWorker of serviceWorkers) {
+        const { registrationFront } = serviceWorker;
+        if (!registrationFront) {
+          continue;
+        }
+
+        const subscription = await registrationFront.getPushSubscription();
+        serviceWorker.subscription = subscription;
+      }
+
+      dispatch({
+        type: REQUEST_WORKERS_SUCCESS,
+        otherWorkers,
+        serviceWorkers,
+        sharedWorkers,
+      });
+    } catch (e) {
+      dispatch({ type: REQUEST_WORKERS_FAILURE, error: e });
+    }
+  };
+}
+
+function startServiceWorker(registrationFront) {
+  return async () => {
+    try {
+      await registrationFront.start();
+    } catch (e) {
+      console.error(e);
+    }
+  };
+}
+
+function unregisterServiceWorker(registrationFront) {
+  return async () => {
+    try {
+      await registrationFront.unregister();
+    } catch (e) {
+      console.error(e);
+    }
+  };
+}
+
+module.exports = {
+  inspectDebugTarget,
+  installTemporaryExtension,
+  pushServiceWorker,
+  reloadTemporaryExtension,
+  removeTemporaryExtension,
+  requestTabs,
+  requestExtensions,
+  requestProcesses,
+  requestWorkers,
+  startServiceWorker,
+  terminateExtensionBackgroundScript,
+  unregisterServiceWorker,
+};
diff --git a/devtools/client/aboutdebugging/src/actions/index.js b/devtools/client/aboutdebugging/src/actions/index.js
new file mode 100644
index 0000000000..797d2c5831
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/actions/index.js
@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const debugTargets = require("resource://devtools/client/aboutdebugging/src/actions/debug-targets.js");
+const runtimes = require("resource://devtools/client/aboutdebugging/src/actions/runtimes.js");
+const telemetry = require("resource://devtools/client/aboutdebugging/src/actions/telemetry.js");
+const ui = require("resource://devtools/client/aboutdebugging/src/actions/ui.js");
+
+Object.assign(exports, ui, runtimes, telemetry, debugTargets);
diff --git a/devtools/client/aboutdebugging/src/actions/moz.build b/devtools/client/aboutdebugging/src/actions/moz.build
new file mode 100644
index 0000000000..a750640d06
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/actions/moz.build
@@ -0,0 +1,11 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "debug-targets.js",
+    "index.js",
+    "runtimes.js",
+    "telemetry.js",
+    "ui.js",
+)
diff --git a/devtools/client/aboutdebugging/src/actions/runtimes.js b/devtools/client/aboutdebugging/src/actions/runtimes.js
new file mode 100644
index 0000000000..fba620951e
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/actions/runtimes.js
@@ -0,0 +1,515 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+
+const {
+  getAllRuntimes,
+  getCurrentRuntime,
+  findRuntimeById,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js");
+
+const {
+  l10n,
+} = require("resource://devtools/client/aboutdebugging/src/modules/l10n.js");
+const {
+  setDefaultPreferencesIfNeeded,
+  DEFAULT_PREFERENCES,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtime-default-preferences.js");
+const {
+  createClientForRuntime,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtime-client-factory.js");
+const {
+  isSupportedDebugTargetPane,
+} = require("resource://devtools/client/aboutdebugging/src/modules/debug-target-support.js");
+
+const {
+  remoteClientManager,
+} = require("resource://devtools/client/shared/remote-debugging/remote-client-manager.js");
+
+const {
+  CONNECT_RUNTIME_CANCEL,
+  CONNECT_RUNTIME_FAILURE,
+  CONNECT_RUNTIME_NOT_RESPONDING,
+  CONNECT_RUNTIME_START,
+  CONNECT_RUNTIME_SUCCESS,
+  DEBUG_TARGET_PANE,
+  DISCONNECT_RUNTIME_FAILURE,
+  DISCONNECT_RUNTIME_START,
+  DISCONNECT_RUNTIME_SUCCESS,
+  PAGE_TYPES,
+  REMOTE_RUNTIMES_UPDATED,
+  RUNTIME_PREFERENCE,
+  RUNTIMES,
+  THIS_FIREFOX_RUNTIME_CREATED,
+  UNWATCH_RUNTIME_FAILURE,
+  UNWATCH_RUNTIME_START,
+  UNWATCH_RUNTIME_SUCCESS,
+  UPDATE_CONNECTION_PROMPT_SETTING_FAILURE,
+  UPDATE_CONNECTION_PROMPT_SETTING_START,
+  UPDATE_CONNECTION_PROMPT_SETTING_SUCCESS,
+  WATCH_RUNTIME_FAILURE,
+  WATCH_RUNTIME_START,
+  WATCH_RUNTIME_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const CONNECTION_TIMING_OUT_DELAY = 3000;
+const CONNECTION_CANCEL_DELAY = 13000;
+
+async function getRuntimeIcon(runtime, channel) {
+  if (runtime.isFenix) {
+    switch (channel) {
+      case "release":
+      case "beta":
+        return "chrome://devtools/skin/images/aboutdebugging-fenix.svg";
+      case "aurora":
+      default:
+        return "chrome://devtools/skin/images/aboutdebugging-fenix-nightly.svg";
+    }
+  }
+
+  return channel === "release" || channel === "beta" || channel === "aurora"
+    ? `chrome://devtools/skin/images/aboutdebugging-firefox-${channel}.svg`
+    : "chrome://devtools/skin/images/aboutdebugging-firefox-nightly.svg";
+}
+
+function onRemoteDevToolsClientClosed() {
+  window.AboutDebugging.onNetworkLocationsUpdated();
+  window.AboutDebugging.onUSBRuntimesUpdated();
+}
+
+function connectRuntime(id) {
+  // Create a random connection id to track the connection attempt in telemetry.
+  const connectionId = (Math.random() * 100000) | 0;
+
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: CONNECT_RUNTIME_START, connectionId, id });
+
+    // The preferences test-connection-timing-out-delay and test-connection-cancel-delay
+    // don't have a default value but will be overridden during our tests.
+    const connectionTimingOutDelay = Services.prefs.getIntPref(
+      "devtools.aboutdebugging.test-connection-timing-out-delay",
+      CONNECTION_TIMING_OUT_DELAY
+    );
+    const connectionCancelDelay = Services.prefs.getIntPref(
+      "devtools.aboutdebugging.test-connection-cancel-delay",
+      CONNECTION_CANCEL_DELAY
+    );
+
+    const connectionNotRespondingTimer = setTimeout(() => {
+      // If connecting to the runtime takes time over CONNECTION_TIMING_OUT_DELAY,
+      // we assume the connection prompt is showing on the runtime, show a dialog
+      // to let user know that.
+      dispatch({ type: CONNECT_RUNTIME_NOT_RESPONDING, connectionId, id });
+    }, connectionTimingOutDelay);
+    const connectionCancelTimer = setTimeout(() => {
+      // Connect button of the runtime will be disabled during connection, but the status
+      // continues till the connection was either succeed or failed. This may have a
+      // possibility that the disabling continues unless page reloading, user will not be
+      // able to click again. To avoid this, revert the connect button status after
+      // CONNECTION_CANCEL_DELAY ms.
+      dispatch({ type: CONNECT_RUNTIME_CANCEL, connectionId, id });
+    }, connectionCancelDelay);
+
+    try {
+      const runtime = findRuntimeById(id, getState().runtimes);
+      const clientWrapper = await createClientForRuntime(runtime);
+
+      await setDefaultPreferencesIfNeeded(clientWrapper, DEFAULT_PREFERENCES);
+
+      const deviceDescription = await clientWrapper.getDeviceDescription();
+      const compatibilityReport =
+        await clientWrapper.checkVersionCompatibility();
+      const icon = await getRuntimeIcon(runtime, deviceDescription.channel);
+
+      const {
+        CONNECTION_PROMPT,
+        PERMANENT_PRIVATE_BROWSING,
+        SERVICE_WORKERS_ENABLED,
+      } = RUNTIME_PREFERENCE;
+      const connectionPromptEnabled = await clientWrapper.getPreference(
+        CONNECTION_PROMPT,
+        false
+      );
+      const privateBrowsing = await clientWrapper.getPreference(
+        PERMANENT_PRIVATE_BROWSING,
+        false
+      );
+      const serviceWorkersEnabled = await clientWrapper.getPreference(
+        SERVICE_WORKERS_ENABLED,
+        true
+      );
+      const serviceWorkersAvailable = serviceWorkersEnabled && !privateBrowsing;
+
+      // Fenix specific workarounds are needed until we can get proper server side APIs
+      // to detect Fenix and get the proper application names and versions.
+      // See https://github.com/mozilla-mobile/fenix/issues/2016.
+
+      // For Fenix runtimes, the ADB runtime name is more accurate than the one returned
+      // by the Device actor.
+      const runtimeName = runtime.isFenix
+        ? runtime.name
+        : deviceDescription.name;
+
+      // For Fenix runtimes, the version we should display is the application version
+      // retrieved from ADB, and not the Gecko version returned by the Device actor.
+      const version = runtime.isFenix
+        ? runtime.extra.adbPackageVersion
+        : deviceDescription.version;
+
+      const runtimeDetails = {
+        canDebugServiceWorkers: deviceDescription.canDebugServiceWorkers,
+        clientWrapper,
+        compatibilityReport,
+        connectionPromptEnabled,
+        info: {
+          deviceName: deviceDescription.deviceName,
+          icon,
+          isFenix: runtime.isFenix,
+          name: runtimeName,
+          os: deviceDescription.os,
+          type: runtime.type,
+          version,
+        },
+        serviceWorkersAvailable,
+      };
+
+      if (runtime.type !== RUNTIMES.THIS_FIREFOX) {
+        // `closed` event will be emitted when disabling remote debugging
+        // on the connected remote runtime.
+        clientWrapper.once("closed", onRemoteDevToolsClientClosed);
+      }
+
+      dispatch({
+        type: CONNECT_RUNTIME_SUCCESS,
+        connectionId,
+        runtime: {
+          id,
+          runtimeDetails,
+          type: runtime.type,
+        },
+      });
+    } catch (e) {
+      dispatch({ type: CONNECT_RUNTIME_FAILURE, connectionId, id, error: e });
+    } finally {
+      clearTimeout(connectionNotRespondingTimer);
+      clearTimeout(connectionCancelTimer);
+    }
+  };
+}
+
+function createThisFirefoxRuntime() {
+  return ({ dispatch, getState }) => {
+    const thisFirefoxRuntime = {
+      id: RUNTIMES.THIS_FIREFOX,
+      isConnecting: false,
+      isConnectionFailed: false,
+      isConnectionNotResponding: false,
+      isConnectionTimeout: false,
+      isUnavailable: false,
+      isUnplugged: false,
+      name: l10n.getString("about-debugging-this-firefox-runtime-name"),
+      type: RUNTIMES.THIS_FIREFOX,
+    };
+    dispatch({
+      type: THIS_FIREFOX_RUNTIME_CREATED,
+      runtime: thisFirefoxRuntime,
+    });
+  };
+}
+
+function disconnectRuntime(id, shouldRedirect = false) {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: DISCONNECT_RUNTIME_START });
+    try {
+      const runtime = findRuntimeById(id, getState().runtimes);
+      const { clientWrapper } = runtime.runtimeDetails;
+
+      if (runtime.type !== RUNTIMES.THIS_FIREFOX) {
+        clientWrapper.off("closed", onRemoteDevToolsClientClosed);
+      }
+      await clientWrapper.close();
+      if (shouldRedirect) {
+        await dispatch(
+          Actions.selectPage(PAGE_TYPES.RUNTIME, RUNTIMES.THIS_FIREFOX)
+        );
+      }
+
+      dispatch({
+        type: DISCONNECT_RUNTIME_SUCCESS,
+        runtime: {
+          id,
+          type: runtime.type,
+        },
+      });
+    } catch (e) {
+      dispatch({ type: DISCONNECT_RUNTIME_FAILURE, error: e });
+    }
+  };
+}
+
+function updateConnectionPromptSetting(connectionPromptEnabled) {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: UPDATE_CONNECTION_PROMPT_SETTING_START });
+    try {
+      const runtime = getCurrentRuntime(getState().runtimes);
+      const { clientWrapper } = runtime.runtimeDetails;
+      const promptPrefName = RUNTIME_PREFERENCE.CONNECTION_PROMPT;
+      await clientWrapper.setPreference(
+        promptPrefName,
+        connectionPromptEnabled
+      );
+      // Re-get actual value from the runtime.
+      connectionPromptEnabled = await clientWrapper.getPreference(
+        promptPrefName,
+        connectionPromptEnabled
+      );
+
+      dispatch({
+        type: UPDATE_CONNECTION_PROMPT_SETTING_SUCCESS,
+        connectionPromptEnabled,
+        runtime,
+      });
+    } catch (e) {
+      dispatch({ type: UPDATE_CONNECTION_PROMPT_SETTING_FAILURE, error: e });
+    }
+  };
+}
+
+function watchRuntime(id) {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: WATCH_RUNTIME_START });
+
+    try {
+      if (id === RUNTIMES.THIS_FIREFOX) {
+        // THIS_FIREFOX connects and disconnects on the fly when opening the page.
+        await dispatch(connectRuntime(RUNTIMES.THIS_FIREFOX));
+      }
+
+      // The selected runtime should already have a connected client assigned.
+      const runtime = findRuntimeById(id, getState().runtimes);
+      await dispatch({ type: WATCH_RUNTIME_SUCCESS, runtime });
+
+      dispatch(Actions.requestExtensions());
+      // we have to wait for tabs, otherwise the requests to getTarget may interfer
+      // with listProcesses
+      await dispatch(Actions.requestTabs());
+      dispatch(Actions.requestWorkers());
+
+      if (
+        isSupportedDebugTargetPane(
+          runtime.runtimeDetails.info.type,
+          DEBUG_TARGET_PANE.PROCESSES
+        )
+      ) {
+        dispatch(Actions.requestProcesses());
+      }
+    } catch (e) {
+      dispatch({ type: WATCH_RUNTIME_FAILURE, error: e });
+    }
+  };
+}
+
+function unwatchRuntime(id) {
+  return async ({ dispatch, getState }) => {
+    const runtime = findRuntimeById(id, getState().runtimes);
+
+    dispatch({ type: UNWATCH_RUNTIME_START, runtime });
+
+    try {
+      if (id === RUNTIMES.THIS_FIREFOX) {
+        // THIS_FIREFOX connects and disconnects on the fly when opening the page.
+        await dispatch(disconnectRuntime(RUNTIMES.THIS_FIREFOX));
+      }
+
+      dispatch({ type: UNWATCH_RUNTIME_SUCCESS });
+    } catch (e) {
+      dispatch({ type: UNWATCH_RUNTIME_FAILURE, error: e });
+    }
+  };
+}
+
+function updateNetworkRuntimes(locations) {
+  const runtimes = locations.map(location => {
+    const [host, port] = location.split(":");
+    return {
+      id: location,
+      extra: {
+        connectionParameters: { host, port: parseInt(port, 10) },
+      },
+      isConnecting: false,
+      isConnectionFailed: false,
+      isConnectionNotResponding: false,
+      isConnectionTimeout: false,
+      isFenix: false,
+      isUnavailable: false,
+      isUnplugged: false,
+      isUnknown: false,
+      name: location,
+      type: RUNTIMES.NETWORK,
+    };
+  });
+  return updateRemoteRuntimes(runtimes, RUNTIMES.NETWORK);
+}
+
+function updateUSBRuntimes(adbRuntimes) {
+  const runtimes = adbRuntimes.map(adbRuntime => {
+    // Set connectionParameters only for known runtimes.
+    const socketPath = adbRuntime.socketPath;
+    const deviceId = adbRuntime.deviceId;
+    const connectionParameters = socketPath ? { deviceId, socketPath } : null;
+    return {
+      id: adbRuntime.id,
+      extra: {
+        connectionParameters,
+        deviceName: adbRuntime.deviceName,
+        adbPackageVersion: adbRuntime.versionName,
+      },
+      isConnecting: false,
+      isConnectionFailed: false,
+      isConnectionNotResponding: false,
+      isConnectionTimeout: false,
+      isFenix: adbRuntime.isFenix,
+      isUnavailable: adbRuntime.isUnavailable,
+      isUnplugged: adbRuntime.isUnplugged,
+      name: adbRuntime.shortName,
+      type: RUNTIMES.USB,
+    };
+  });
+  return updateRemoteRuntimes(runtimes, RUNTIMES.USB);
+}
+
+/**
+ * Check that a given runtime can still be found in the provided array of runtimes, and
+ * that the connection of the associated DevToolsClient is still valid.
+ * Note that this check is only valid for runtimes which match the type of the runtimes
+ * in the array.
+ */
+function _isRuntimeValid(runtime, runtimes) {
+  const isRuntimeAvailable = runtimes.some(r => r.id === runtime.id);
+  const isConnectionValid =
+    runtime.runtimeDetails && !runtime.runtimeDetails.clientWrapper.isClosed();
+  return isRuntimeAvailable && isConnectionValid;
+}
+
+function updateRemoteRuntimes(runtimes, type) {
+  return async ({ dispatch, getState }) => {
+    const currentRuntime = getCurrentRuntime(getState().runtimes);
+
+    // Check if the updated remote runtimes should trigger a navigation out of the current
+    // runtime page.
+    if (
+      currentRuntime &&
+      currentRuntime.type === type &&
+      !_isRuntimeValid(currentRuntime, runtimes)
+    ) {
+      // Since current remote runtime is invalid, move to this firefox page.
+      // This case is considered as followings and so on:
+      // * Remove ADB addon
+      // * (Physically) Disconnect USB runtime
+      //
+      // The reason we call selectPage before REMOTE_RUNTIMES_UPDATED is fired is below.
+      // Current runtime can not be retrieved after REMOTE_RUNTIMES_UPDATED action, since
+      // that updates runtime state. So, before that we fire selectPage action to execute
+      // `unwatchRuntime` correctly.
+      await dispatch(
+        Actions.selectPage(PAGE_TYPES.RUNTIME, RUNTIMES.THIS_FIREFOX)
+      );
+    }
+
+    // For existing runtimes, transfer all properties that are not available in the
+    // runtime objects passed to this method:
+    // - runtimeDetails (set by about:debugging after a successful connection)
+    // - isConnecting (set by about:debugging during the connection)
+    // - isConnectionFailed (set by about:debugging if connection was failed)
+    // - isConnectionNotResponding
+    //     (set by about:debugging if connection is taking too much time)
+    // - isConnectionTimeout (set by about:debugging if connection was timeout)
+    runtimes.forEach(runtime => {
+      const existingRuntime = findRuntimeById(runtime.id, getState().runtimes);
+      const isConnectionValid =
+        existingRuntime?.runtimeDetails &&
+        !existingRuntime.runtimeDetails.clientWrapper.isClosed();
+      runtime.runtimeDetails = isConnectionValid
+        ? existingRuntime.runtimeDetails
+        : null;
+      runtime.isConnecting = existingRuntime
+        ? existingRuntime.isConnecting
+        : false;
+      runtime.isConnectionFailed = existingRuntime
+        ? existingRuntime.isConnectionFailed
+        : false;
+      runtime.isConnectionNotResponding = existingRuntime
+        ? existingRuntime.isConnectionNotResponding
+        : false;
+      runtime.isConnectionTimeout = existingRuntime
+        ? existingRuntime.isConnectionTimeout
+        : false;
+    });
+
+    const existingRuntimes = getAllRuntimes(getState().runtimes);
+    for (const runtime of existingRuntimes) {
+      // Runtime was connected before.
+      const isConnected = runtime.runtimeDetails;
+      // Runtime is of the same type as the updated runtimes array, so we should check it.
+      const isSameType = runtime.type === type;
+      if (isConnected && isSameType && !_isRuntimeValid(runtime, runtimes)) {
+        // Disconnect runtimes that were no longer valid.
+        await dispatch(disconnectRuntime(runtime.id));
+      }
+    }
+
+    dispatch({ type: REMOTE_RUNTIMES_UPDATED, runtimes, runtimeType: type });
+
+    for (const runtime of getAllRuntimes(getState().runtimes)) {
+      if (runtime.type !== type) {
+        continue;
+      }
+
+      // Reconnect clients already available in the RemoteClientManager.
+      const isConnected = !!runtime.runtimeDetails;
+      const hasConnectedClient = remoteClientManager.hasClient(
+        runtime.id,
+        runtime.type
+      );
+      if (!isConnected && hasConnectedClient) {
+        await dispatch(connectRuntime(runtime.id));
+      }
+    }
+  };
+}
+
+/**
+ * Remove all the listeners added on client objects. Since those objects are persisted
+ * regardless of the about:debugging lifecycle, all the added events should be removed
+ * before leaving about:debugging.
+ */
+function removeRuntimeListeners() {
+  return ({ dispatch, getState }) => {
+    const allRuntimes = getAllRuntimes(getState().runtimes);
+    const remoteRuntimes = allRuntimes.filter(
+      r => r.type !== RUNTIMES.THIS_FIREFOX
+    );
+    for (const runtime of remoteRuntimes) {
+      if (runtime.runtimeDetails) {
+        const { clientWrapper } = runtime.runtimeDetails;
+        clientWrapper.off("closed", onRemoteDevToolsClientClosed);
+      }
+    }
+  };
+}
+
+module.exports = {
+  connectRuntime,
+  createThisFirefoxRuntime,
+  disconnectRuntime,
+  removeRuntimeListeners,
+  unwatchRuntime,
+  updateConnectionPromptSetting,
+  updateNetworkRuntimes,
+  updateUSBRuntimes,
+  watchRuntime,
+};
diff --git a/devtools/client/aboutdebugging/src/actions/telemetry.js b/devtools/client/aboutdebugging/src/actions/telemetry.js
new file mode 100644
index 0000000000..b418c77a50
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/actions/telemetry.js
@@ -0,0 +1,23 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  TELEMETRY_RECORD,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * If a given event cannot be mapped to an existing action, use this action that will only
+ * be processed by the event recording middleware.
+ */
+function recordTelemetryEvent(method, details) {
+  return ({ dispatch, getState }) => {
+    dispatch({ type: TELEMETRY_RECORD, method, details });
+  };
+}
+
+module.exports = {
+  recordTelemetryEvent,
+};
diff --git a/devtools/client/aboutdebugging/src/actions/ui.js b/devtools/client/aboutdebugging/src/actions/ui.js
new file mode 100644
index 0000000000..fb676cefd6
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/actions/ui.js
@@ -0,0 +1,202 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  ADB_ADDON_INSTALL_START,
+  ADB_ADDON_INSTALL_SUCCESS,
+  ADB_ADDON_INSTALL_FAILURE,
+  ADB_ADDON_UNINSTALL_START,
+  ADB_ADDON_UNINSTALL_SUCCESS,
+  ADB_ADDON_UNINSTALL_FAILURE,
+  ADB_ADDON_STATUS_UPDATED,
+  ADB_READY_UPDATED,
+  DEBUG_TARGET_COLLAPSIBILITY_UPDATED,
+  HIDE_PROFILER_DIALOG,
+  NETWORK_LOCATIONS_UPDATE_FAILURE,
+  NETWORK_LOCATIONS_UPDATE_START,
+  NETWORK_LOCATIONS_UPDATE_SUCCESS,
+  PAGE_TYPES,
+  SELECT_PAGE_FAILURE,
+  SELECT_PAGE_START,
+  SELECT_PAGE_SUCCESS,
+  SELECTED_RUNTIME_ID_UPDATED,
+  SHOW_PROFILER_DIALOG,
+  SWITCH_PROFILER_CONTEXT,
+  USB_RUNTIMES_SCAN_START,
+  USB_RUNTIMES_SCAN_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const NetworkLocationsModule = require("resource://devtools/client/aboutdebugging/src/modules/network-locations.js");
+const {
+  adbAddon,
+} = require("resource://devtools/client/shared/remote-debugging/adb/adb-addon.js");
+const {
+  refreshUSBRuntimes,
+} = require("resource://devtools/client/aboutdebugging/src/modules/usb-runtimes.js");
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+
+function selectPage(page, runtimeId) {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: SELECT_PAGE_START });
+
+    try {
+      const isSamePage = (oldPage, newPage) => {
+        if (newPage === PAGE_TYPES.RUNTIME && oldPage === PAGE_TYPES.RUNTIME) {
+          return runtimeId === getState().runtimes.selectedRuntimeId;
+        }
+        return newPage === oldPage;
+      };
+
+      if (!page) {
+        throw new Error("No page provided.");
+      }
+
+      const currentPage = getState().ui.selectedPage;
+      // Nothing to dispatch if the page is the same as the current page
+      if (isSamePage(currentPage, page)) {
+        return;
+      }
+
+      // Stop showing the profiler dialog if we are navigating to another page.
+      if (getState().ui.showProfilerDialog) {
+        await dispatch({ type: HIDE_PROFILER_DIALOG });
+      }
+
+      // Stop watching current runtime, if currently on a RUNTIME page.
+      if (currentPage === PAGE_TYPES.RUNTIME) {
+        const currentRuntimeId = getState().runtimes.selectedRuntimeId;
+        await dispatch(Actions.unwatchRuntime(currentRuntimeId));
+      }
+
+      // Always update the selected runtime id.
+      // If we are navigating to a non-runtime page, the Runtime page components are no
+      // longer rendered so it is safe to nullify the runtimeId.
+      // If we are navigating to a runtime page, the runtime corresponding to runtimeId
+      // is already connected, so components can safely get runtimeDetails on this new
+      // runtime.
+      dispatch({ type: SELECTED_RUNTIME_ID_UPDATED, runtimeId });
+
+      // Start watching current runtime, if moving to a RUNTIME page.
+      if (page === PAGE_TYPES.RUNTIME) {
+        await dispatch(Actions.watchRuntime(runtimeId));
+      }
+
+      dispatch({ type: SELECT_PAGE_SUCCESS, page });
+    } catch (e) {
+      dispatch({ type: SELECT_PAGE_FAILURE, error: e });
+    }
+  };
+}
+
+function updateDebugTargetCollapsibility(key, isCollapsed) {
+  return { type: DEBUG_TARGET_COLLAPSIBILITY_UPDATED, key, isCollapsed };
+}
+
+function addNetworkLocation(location) {
+  return ({ dispatch, getState }) => {
+    NetworkLocationsModule.addNetworkLocation(location);
+  };
+}
+
+function removeNetworkLocation(location) {
+  return ({ dispatch, getState }) => {
+    NetworkLocationsModule.removeNetworkLocation(location);
+  };
+}
+
+function showProfilerDialog() {
+  return { type: SHOW_PROFILER_DIALOG };
+}
+
+/**
+ * The profiler can switch between "devtools-remote" and "aboutprofiling-remote"
+ * page contexts.
+ */
+function switchProfilerContext(profilerContext) {
+  return { type: SWITCH_PROFILER_CONTEXT, profilerContext };
+}
+
+function hideProfilerDialog() {
+  return { type: HIDE_PROFILER_DIALOG };
+}
+
+function updateAdbAddonStatus(adbAddonStatus) {
+  return { type: ADB_ADDON_STATUS_UPDATED, adbAddonStatus };
+}
+
+function updateAdbReady(isAdbReady) {
+  return { type: ADB_READY_UPDATED, isAdbReady };
+}
+
+function updateNetworkLocations(locations) {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: NETWORK_LOCATIONS_UPDATE_START });
+    try {
+      await dispatch(Actions.updateNetworkRuntimes(locations));
+      dispatch({ type: NETWORK_LOCATIONS_UPDATE_SUCCESS, locations });
+    } catch (e) {
+      dispatch({ type: NETWORK_LOCATIONS_UPDATE_FAILURE, error: e });
+    }
+  };
+}
+
+function installAdbAddon() {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: ADB_ADDON_INSTALL_START });
+
+    try {
+      // "aboutdebugging" will be forwarded to telemetry as the installation source
+      // for the addon.
+      await adbAddon.install("about:debugging");
+      dispatch({ type: ADB_ADDON_INSTALL_SUCCESS });
+    } catch (e) {
+      dispatch({ type: ADB_ADDON_INSTALL_FAILURE, error: e });
+    }
+  };
+}
+
+function uninstallAdbAddon() {
+  return async ({ dispatch, getState }) => {
+    dispatch({ type: ADB_ADDON_UNINSTALL_START });
+
+    try {
+      await adbAddon.uninstall();
+      dispatch({ type: ADB_ADDON_UNINSTALL_SUCCESS });
+    } catch (e) {
+      dispatch({ type: ADB_ADDON_UNINSTALL_FAILURE, error: e });
+    }
+  };
+}
+
+function scanUSBRuntimes() {
+  return async ({ dispatch, getState }) => {
+    // do not re-scan if we are already doing it
+    if (getState().ui.isScanningUsb) {
+      return;
+    }
+
+    dispatch({ type: USB_RUNTIMES_SCAN_START });
+    await refreshUSBRuntimes();
+    dispatch({ type: USB_RUNTIMES_SCAN_SUCCESS });
+  };
+}
+
+module.exports = {
+  addNetworkLocation,
+  hideProfilerDialog,
+  installAdbAddon,
+  removeNetworkLocation,
+  scanUSBRuntimes,
+  selectPage,
+  showProfilerDialog,
+  switchProfilerContext,
+  uninstallAdbAddon,
+  updateAdbAddonStatus,
+  updateAdbReady,
+  updateDebugTargetCollapsibility,
+  updateNetworkLocations,
+};
diff --git a/devtools/client/aboutdebugging/src/base.css b/devtools/client/aboutdebugging/src/base.css
new file mode 100644
index 0000000000..728cbeed0c
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/base.css
@@ -0,0 +1,521 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+:root {
+  /* Colors from common.css */
+  --in-content-background-color: f9f9fa;
+  --in-content-border-color: #d7d7db;
+  --in-content-primary-button-background: rgb(0, 97, 224);
+  --in-content-primary-button-background-active: rgb(5, 62, 148);
+  --in-content-primary-button-background-hover: rgb(2, 80, 187);
+  --in-content-text-color: #0c0c0d;
+
+  --bg-color: var(--in-content-background-color);
+  --text-color: var(--in-content-text-color);
+  --secondary-text-color: var(--grey-50);
+
+  --border-color: var(--in-content-border-color);
+
+  --box-background: #fff;
+  --box-border-color: var(--in-content-border-color);
+
+  --button-background-color: var(--grey-90-a10); /* Note: this is from Photon Default button */
+  --button-color: var(--grey-90); /* Note: this is from Photon Default button */
+  --button-hover-background-color: var(--grey-90-a20); /* Note: this is from Photon Default button */
+  --button-active-background-color: var(--grey-90-a30); /* Note: this is from Photon Default button */
+
+  --category-background-hover: rgba(12,12,13,0.1);
+  --category-text: rgba(12,12,13);
+  --category-text-selected: var(--in-content-primary-button-background);
+
+  --fieldpair-text-color: var(--grey-50);
+
+  --sidebar-text-color: var(--category-text);
+  --sidebar-selected-color: var(--category-text-selected);
+  --sidebar-background-hover: var(--category-background-hover);
+
+  --card-background-color: var(--white-100);
+  --card-separator-color: var(--grey-20);
+
+  /* Dimensions from common.css #categories > .category */
+  /* TODO: Values are not based on photon's 4px base distance, see bug 1501638 */
+  --category-height: 48px;
+  --category-padding: 10px;
+  --category-transition-duration: 150ms;
+
+  --icon-ok-color: var(--green-70);
+  --icon-info-color: var(--grey-90);
+
+  --link-color: var(--in-content-primary-button-background);
+  --link-color-active: var(--in-content-primary-button-background-active);
+  --link-color-hover: var(--in-content-primary-button-background-hover);
+
+  --primary-button-background-color: var(--blue-60);
+  --primary-button-color: var(--white-100);
+  --primary-button-hover-background-color: var(--blue-70);
+  --primary-button-active-background-color: var(--blue-80);
+
+  --popup-header-background-color: var(--grey-20);
+  --popup-header-color: var(--grey-90);
+
+  /* Colors from Photon */
+  --success-background: #30e60b;
+  --warning-background: #fffbd6; /* from the Web Console */
+  --warning-border: rgba(164, 127, 0, 0.27); /* yellow-70(#a47f00) at 27% */
+  --warning-icon: var(--yellow-65); /* from the Web Console */
+  --warning-text: var(--yellow-80); /* from the Web Console */
+  --error-background: #fdf2f5; /* from the Web Console */
+  --error-border: rgba(90, 0, 2, 0.16); /*  red-80(#5a0002) at 16% */
+  --error-icon: var(--red-60); /* from the Web Console */
+  --error-text: var(--red-70); /* from the Web Console */
+  --highlight-50: #0a84ff;
+  --grey-20: #ededf0; /* for ui, no special semantic */
+  --grey-30: #d7d7db; /* for ui, no special semantic */
+  --grey-50: #737373; /* for ui, no special semantic */
+  --grey-90: #0c0c0d; /* for ui, no special semantic */
+  --grey-90-a10: rgba(12, 12, 13, 0.1);
+  --grey-90-a20: rgba(12, 12, 13, 0.2);
+  --grey-90-a30: rgba(12, 12, 13, 0.3);
+  --grey-90-a60: rgba(12, 12, 13, 0.6);
+  --red-70: #a4000f; /* for ui, no special semantic */
+  --white-100: #fff; /* for ui, no special semantic */
+  --yellow-60: #d7b600; /* for ui, no special semantic */
+  --yellow-70: #a47f00; /* for ui, no special semantic */
+
+  /* Typography from Photon */
+  /* See https://firefox-dev.tools/photon/visuals/typography.html */
+  --body-10-font-size: 13px;
+  --body-10-font-weight: 400;
+  --body-20-font-size: 15px;
+  --body-20-font-weight: 400;
+  --body-20-font-weight-bold: 700;
+  --caption-10-font-size: 11px;
+  --caption-10-font-weight: 400;
+  --caption-20-font-size: 13px;
+  --caption-20-font-weight: 400;
+  --display-10-font-size: 28px;
+  --display-10-font-weight: 200;
+  --title-20-font-size: 17px;
+  --title-20-font-weight: 600;
+  --title-30-font-size: 22px;
+  --title-30-font-weight: 300;
+
+  /* Global layout vars */
+  --page-width: 664px;
+  --base-unit: 4px;
+
+  /* Global styles */
+  --base-font-style: message-box;
+  --base-font-size: var(--body-10-font-size);
+  --base-font-weight: var(--body-10-font-weight);
+  --base-line-height: 1.8;
+  --icon-label-font-size: var(--body-10-font-size);
+  --message-font-size: var(--body-10-font-size);
+  --button-font-size: var(--base-font-size);
+  --micro-font-size: 11px;
+  --monospace-font-family: monospace;
+
+  --card-shadow-blur-radius: var(--base-unit);
+
+
+  /*
+   * Variables particular to about:debugging
+   */
+  --alt-heading-icon-size: calc(var(--base-unit) * 6);
+  --alt-heading-icon-gap: var(--base-unit);
+  --main-heading-icon-size: calc(var(--base-unit) * 17); /* 4px * 17 = 68px */
+  --main-heading-icon-gap: calc(var(--base-unit) * 3);
+  --main-subheading-icon-size: calc(var(--base-unit) * 4);
+  --main-subheading-heading-icon-gap: calc(var(--base-unit) * 2);
+}
+
+/* Dark Theme variables */
+
+@media  (prefers-color-scheme: dark) {
+  :root {
+    --in-content-background-color: rgb(28, 27, 34);
+    --in-content-border-color: rgba(249,249,250,0.2);
+    --in-content-primary-button-background: #00ddff;
+    --in-content-primary-button-background-active: rgb(170,242,255);
+    --in-content-primary-button-background-hover: rgb(128,235,255);
+    --in-content-text-color: #eee;
+
+    --secondary-text-color: rgb(168, 168, 168);
+
+    --box-background: rgb(35, 34, 43);
+
+    --button-background-color: rgb(72, 72, 84);
+    --button-color: var(--white-100);
+    --button-hover-background-color: rgb(92, 92, 106);
+
+    --category-background-hover: rgba(12,12,13,0.1);
+    --category-text: var(--text-color);
+
+    --fieldpair-text-color: var(--text-color);
+
+    --sidebar-text-color: var(--text-color);
+    --sidebar-background-hover: rgb(92, 92, 106);
+
+    --card-background-color: rgb(35, 34, 43);
+    --card-separator-color: var(--grey-50);
+
+    --icon-ok-color: var(--white-100);
+    --icon-info-color: var(--white-100);
+
+    --popup-header-background-color: var(--grey-50);
+    --popup-header-color: var(--white-100);
+
+    /*
+     * From common.inc.css
+     * https://searchfox.org/mozilla-central/rev/b52cf6bbe214bd9d93ed9333d0403f7d556ad7c8/toolkit/themes/shared/in-content/common.inc.css#165-168
+     */
+    --primary-button-background-color: #00ddff;
+    --primary-button-color: rgb(43,42,51);
+    --primary-button-active-background-color: rgb(170,242,255);
+    --primary-button-hover-background-color: rgb(128,235,255);
+  }
+}
+
+/*
+* Reset some tags
+*/
+
+html {
+  font: var(--base-font-style);
+}
+
+body {
+  margin: 0;
+  padding: 0;
+  color: var(--text-color);
+  font-size: var(--base-font-size);
+  font-weight: var(--base-font-weight);
+  line-height: var(--base-line-height);
+  background: var(--bg-color);
+}
+
+dd {
+  margin: 0;
+  padding: 0;
+}
+
+ul {
+  list-style: none;
+  margin: 0;
+  padding: 0;
+}
+
+a {
+  color: var(--link-color);
+}
+a:hover {
+  color: var(--link-color-hover);
+}
+a:active {
+  color: var(--link-color-active);
+}
+
+p, h1 {
+  margin: 0;
+}
+
+/*
+* Utils
+*/
+
+/* text that needs to be cut with … */
+.ellipsis-text {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+/* Technical text that should use a monospace font, such as code, error messages. */
+.technical-text {
+  font-family: var(--monospace-font-family);
+}
+
+/* Links that need to look like current text */
+.undecorated-link,
+.undecorated-link:hover {
+  text-decoration: none;
+  color: currentColor;
+}
+
+/* Text needs to wrap anywhere */
+.word-wrap-anywhere {
+  word-wrap: anywhere;
+}
+
+/*
+* Typography
+*/
+
+/* Main style for heading (i.e. h1) */
+.main-heading {
+  font-size: var(--display-10-font-size);
+  font-weight: var(--display-10-font-weight);
+  line-height: 1.2;
+}
+
+.main-heading__icon {
+  width: 100%;
+}
+
+.main-heading-subtitle {
+  font-size: var(--title-30-font-size);
+  font-weight: var(--title-30-font-weight);
+}
+
+/* Main style for a subheading (i.e. h2). It features an icon */
+/* +--------+-------------+
+*  | [Icon] | Lorem ipsum |
+*  +--------+-------------+
+*/
+.main-subheading {
+  margin-block: calc(var(--base-unit) * 4) 0;
+  font-size: var(--title-20-font-size); /* Note: this is from Photon Title 20 */
+  font-weight: var(--title-20-font-weight); /* Note: this is from Photon Title 20 */
+
+  display: grid;
+  grid-template-columns: var(--main-subheading-icon-size) 1fr;
+  grid-column-gap: var(--main-subheading-heading-icon-gap);
+  align-items: center;
+}
+
+.main-subheading__icon {
+  width: 100%;
+  fill: currentColor;
+  -moz-context-properties: fill;
+}
+
+/* Alternative style for a heading (i.e. h1) */
+.alt-heading {
+  font-weight: var(--title-20-font-weight);
+  font-size: var(--title-20-font-size);
+
+  margin-block-start: 0;
+  margin-block-end: calc(var(--base-unit) * 4);
+}
+
+.alt-heading--larger {
+  font-size: var(--title-30-font-size);
+  font-weight: var(--title-30-font-weight);
+}
+
+/* Alternative style for a subheading (i.e. h2). It features an icon */
+/* +--------+-------------+
+*  | [Icon] | Lorem ipsum |
+*  +--------+-------------+
+*/
+.alt-subheading {
+  margin-block-start: calc(var(--base-unit) * 4);
+  font-weight: 600;
+  font-size: 1.14em;
+  line-height: 1.4em; /* odd value - from common.inc.css */
+
+  display: grid;
+  grid-template-columns: var(--alt-heading-icon-size) 1fr;
+  grid-column-gap: var(--alt-heading-icon-gap);
+  align-items: center;
+}
+
+.alt-subheading__icon {
+  width: 100%;
+  fill: currentColor;
+  -moz-context-properties: fill;
+}
+
+/*
+* Layout elements
+*/
+
+/* for horizontal rules / separators */
+.separator {
+  border-style: solid none none none;
+  border-color: var(--border-color);
+}
+
+/* adds breathing space to the separator */
+.separator--breathe {
+  margin: calc(var(--base-unit) * 5) 0;
+}
+
+/* a series of button-like elements, layed out horizontally */
+.toolbar {
+  display: flex;
+  column-gap: calc(var(--base-unit) * 3);
+}
+
+.toolbar--right-align {
+  justify-content: end;
+}
+
+/*
+Form controls
+*/
+.default-button, .default-input {
+  box-sizing: border-box;
+  font-size: 1em;
+}
+
+/* Buttons from Photon */
+.default-button, .primary-button {
+  appearance: none;
+  margin: 0;
+  height: calc(var(--base-unit) * 8);
+  padding-inline-start: calc(var(--base-unit) * 5);
+  padding-inline-end: calc(var(--base-unit) * 5);
+
+  border: none;
+  border-radius: calc(var(--base-unit) / 2);
+
+  font-size: var(--button-font-size);
+}
+
+/* Disabled state for buttons from Photon */
+.default-button:disabled, .primary-button:disabled {
+  opacity: 0.4;
+}
+
+/* Smaller variant size for buttons, from Photon */
+.default-button--micro, .primary-button--micro {
+  padding-inline-start: calc(2 * var(--base-unit));
+  padding-inline-end: calc(2 * var(--base-unit));
+  font-size: var(--micro-font-size);
+  height: calc(var(--base-unit) * 6);
+}
+
+/* Photon button representing a primary action */
+.primary-button {
+  color: var(--primary-button-color);
+  background-color: var(--primary-button-background-color);
+}
+
+.primary-button:enabled:hover {
+  background: var(--primary-button-hover-background-color);
+}
+
+.primary-button:enabled:active {
+  background: var(--primary-button-active-background-color);
+}
+
+/* Photon standard button */
+.default-button {
+  color: var(--button-color);
+  background-color: var(--button-background-color);
+}
+
+.default-button:enabled:hover {
+  background: var(--button-hover-background-color);
+}
+
+.default-button:enabled:active {
+  background: var(--button-active-background-color);
+}
+
+@media (prefers-contrast) {
+  .default-button,
+  .ghost-button,
+  .primary-button {
+    background-color: ButtonFace;
+    /* Add a border to make buttons visible in high contrast */
+    border: 1px solid ButtonText;
+    color: ButtonText;
+  }
+
+  .ghost-button {
+    fill:  ButtonText;
+  }
+
+  :is(
+    .default-button,
+    .ghost-button,
+    .primary-button
+  ):enabled:is(:hover, :active) {
+    background-color: ButtonText;
+    color: ButtonFace;
+  }
+}
+
+/* Photon ghost button. Icon button with no background */
+.ghost-button {
+  background: transparent;
+  border: none;
+  border-radius: calc(var(--base-unit) / 2);
+  fill: var(--button-color);
+  height: calc(var(--base-unit) * 6);
+  padding: calc(var(--base-unit));
+  width: calc(var(--base-unit) * 6);
+
+  -moz-context-properties: fill;
+}
+
+.ghost-button:hover {
+  background: var(--button-hover-background-color);
+}
+
+.ghost-button:active {
+  background: var(--button-active-background-color);
+}
+
+/* Standard inputs */
+.default-input {
+  line-height: unset;
+  padding: 0 calc(var(--base-unit) * 2);
+  height: 100%;
+
+  border: 1px solid var(--box-border-color);
+  border-radius: 2px;
+  color: var(--text-color);
+  background-color: var(--box-background);
+}
+
+/*
+* Other UI components
+*/
+
+/*
+* A small, colored badge.
+* NOTE: styles borrowed from Photon's micro buttons (there aren't badges)
+*/
+.badge {
+  background: var(--grey-30);
+  border-radius: calc(var(--base-unit) / 2);
+  font-size: var(--micro-font-size);
+  padding: var(--base-unit) calc(2 * var(--base-unit));
+}
+
+.badge--info {
+  background: var(--highlight-50);
+}
+
+.badge--success {
+  background: var(--success-background);
+}
+
+.badge--warning {
+  background: var(--warning-background);
+}
+
+.badge--error {
+  background: var(--error-background);
+}
+
+/*
+ * Card UI, from Photon
+ */
+.card {
+  background-color: var(--card-background-color); /* from common.inc.css */
+  border-radius: var(--card-shadow-blur-radius); /* from common.inc.css */
+  box-shadow: 0 1px 4px var(--grey-90-a10); /* from common.inc.css */
+  box-sizing: border-box;
+  min-width: min-content;
+  padding-block: calc(var(--base-unit) * 5);
+}
+
+.card__heading {
+  font-size: var(--title-20-font-size); /* Note: this is from Photon Title 20 */
+  font-weight: var(--title-20-font-weight); /* Note: this is from Photon Title 20 */
+}
diff --git a/devtools/client/aboutdebugging/src/components/App.css b/devtools/client/aboutdebugging/src/components/App.css
new file mode 100644
index 0000000000..5196ce8e2e
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/App.css
@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * The current layout of about:debugging is
+ *
+ *  +-------------+-------------------------------+
+ *  |   Sidebar   | Page (Runtime or Connect)     |
+ *  |   (240px)   |                               |
+ *  |             |                               |
+ *  +-------------+-------------------------------+
+ *
+ * Some of the values (font sizes, widths, etc.) are the same as
+ * about:preferences, which uses the shared common.css
+ */
+
+.app {
+  /* from common */
+  --sidebar-width: 280px;
+  --app-top-padding: 70px;
+  --app-bottom-padding: 40px;
+  --app-left-padding: 32px;
+  --app-right-padding: 32px;
+
+  box-sizing: border-box;
+  width: 100vw;
+  height: 100vh;
+  overflow: hidden; /* we don't want the sidebar to scroll, only the main content */
+
+  display: grid;
+  grid-column-gap: 40px;
+  grid-template-columns: var(--sidebar-width) auto;
+
+  font-size: var(--base-font-size);
+  font-weight: var(--base-font-weight);
+  line-height: var(--base-line-height);
+}
+
+.app__sidebar {
+  padding-block-start: var(--app-top-padding);
+  padding-block-end: var(--app-bottom-padding);
+  padding-inline-start: var(--app-left-padding);
+}
+
+.app__content {
+  /* we want to scroll only the main content, not the sidebar */
+  overflow-y: auto;
+
+  /* padding will give space for card shadow to appear and
+     margin will correct the alignment */
+  margin-inline-start: calc(var(--card-shadow-blur-radius) * -1);
+  padding-inline: var(--card-shadow-blur-radius);
+  padding-block-start: var(--app-top-padding);
+}
+
+/* Workaround for Gecko clipping the padding-bottom of a scrollable container;
+   we create a block to act as the bottom padding instead. */
+.app__content::after {
+  content: "";
+  display: block;
+  height: var(--app-bottom-padding);
+}
+
+.page {
+  max-width: var(--page-width);
+  min-width: min-content;
+  font-size: var(--body-20-font-size);
+  font-weight: var(--body-20-font-weight);
+  padding-inline-end: var(--app-right-padding);
+}
diff --git a/devtools/client/aboutdebugging/src/components/App.js b/devtools/client/aboutdebugging/src/components/App.js
new file mode 100644
index 0000000000..7bdf3eb0c5
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/App.js
@@ -0,0 +1,213 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  connect,
+} = require("resource://devtools/client/shared/vendor/react-redux.js");
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Route = createFactory(
+  require("resource://devtools/client/shared/vendor/react-router-dom.js").Route
+);
+const Switch = createFactory(
+  require("resource://devtools/client/shared/vendor/react-router-dom.js").Switch
+);
+const Redirect = createFactory(
+  require("resource://devtools/client/shared/vendor/react-router-dom.js")
+    .Redirect
+);
+
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+const {
+  PAGE_TYPES,
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const ConnectPage = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/connect/ConnectPage.js")
+);
+const RuntimePage = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/RuntimePage.js")
+);
+const Sidebar = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/sidebar/Sidebar.js")
+);
+
+class App extends PureComponent {
+  static get propTypes() {
+    return {
+      adbAddonStatus: Types.adbAddonStatus,
+      // The "dispatch" helper is forwarded to the App component via connect.
+      // From that point, components are responsible for forwarding the dispatch
+      // property to all components who need to dispatch actions.
+      dispatch: PropTypes.func.isRequired,
+      // getString prop is injected by the withLocalization wrapper
+      getString: PropTypes.func.isRequired,
+      isAdbReady: PropTypes.bool.isRequired,
+      isScanningUsb: PropTypes.bool.isRequired,
+      networkLocations: PropTypes.arrayOf(Types.location).isRequired,
+      networkRuntimes: PropTypes.arrayOf(Types.runtime).isRequired,
+      selectedPage: Types.page,
+      selectedRuntimeId: PropTypes.string,
+      usbRuntimes: PropTypes.arrayOf(Types.runtime).isRequired,
+    };
+  }
+
+  componentDidUpdate() {
+    this.updateTitle();
+  }
+
+  updateTitle() {
+    const { getString, selectedPage, selectedRuntimeId } = this.props;
+
+    const pageTitle =
+      selectedPage === PAGE_TYPES.RUNTIME
+        ? getString("about-debugging-page-title-runtime-page", {
+            selectedRuntimeId,
+          })
+        : getString("about-debugging-page-title-setup-page");
+
+    document.title = pageTitle;
+  }
+
+  renderConnect() {
+    const { adbAddonStatus, dispatch, networkLocations } = this.props;
+
+    return ConnectPage({
+      adbAddonStatus,
+      dispatch,
+      networkLocations,
+    });
+  }
+
+  // The `match` object here is passed automatically by the Route object.
+  // We are using it to read the route path.
+  // See react-router docs:
+  // https://github.com/ReactTraining/react-router/blob/master/packages/react-router/docs/api/match.md
+  renderRuntime({ match }) {
+    const isRuntimeAvailable = id => {
+      const runtimes = [
+        ...this.props.networkRuntimes,
+        ...this.props.usbRuntimes,
+      ];
+      const runtime = runtimes.find(x => x.id === id);
+      return runtime?.runtimeDetails;
+    };
+
+    const { dispatch } = this.props;
+
+    let runtimeId = match.params.runtimeId || RUNTIMES.THIS_FIREFOX;
+    if (match.params.runtimeId !== RUNTIMES.THIS_FIREFOX) {
+      const rawId = decodeURIComponent(match.params.runtimeId);
+      if (isRuntimeAvailable(rawId)) {
+        runtimeId = rawId;
+      } else {
+        // Also redirect to "This Firefox" if runtime is not found
+        return Redirect({ to: `/runtime/${RUNTIMES.THIS_FIREFOX}` });
+      }
+    }
+
+    // we need to pass a key so the component updates when we want to showcase
+    // a different runtime
+    return RuntimePage({ dispatch, key: runtimeId, runtimeId });
+  }
+
+  renderRoutes() {
+    return Switch(
+      {},
+      Route({
+        path: "/setup",
+        render: () => this.renderConnect(),
+      }),
+      Route({
+        path: "/runtime/:runtimeId",
+        render: routeProps => this.renderRuntime(routeProps),
+      }),
+      // default route when there's no match which includes "/"
+      // TODO: the url does not match "/" means invalid URL,
+      // in this case maybe we'd like to do something else than a redirect.
+      // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1509897
+      Route({
+        render: routeProps => {
+          const { pathname } = routeProps.location;
+          // The old about:debugging supported the following routes:
+          // about:debugging#workers, about:debugging#addons and about:debugging#tabs.
+          // Such links can still be found in external documentation pages.
+          // We redirect to This Firefox rather than the Setup Page here.
+          if (
+            pathname === "/workers" ||
+            pathname === "/addons" ||
+            pathname === "/tabs"
+          ) {
+            return Redirect({ to: `/runtime/${RUNTIMES.THIS_FIREFOX}` });
+          }
+          return Redirect({ to: "/setup" });
+        },
+      })
+    );
+  }
+
+  render() {
+    const {
+      adbAddonStatus,
+      dispatch,
+      isAdbReady,
+      isScanningUsb,
+      networkRuntimes,
+      selectedPage,
+      selectedRuntimeId,
+      usbRuntimes,
+    } = this.props;
+
+    return Localized(
+      {},
+      dom.div(
+        { className: "app" },
+        Sidebar({
+          adbAddonStatus,
+          className: "app__sidebar",
+          dispatch,
+          isAdbReady,
+          isScanningUsb,
+          networkRuntimes,
+          selectedPage,
+          selectedRuntimeId,
+          usbRuntimes,
+        }),
+        dom.main({ className: "app__content" }, this.renderRoutes())
+      )
+    );
+  }
+}
+
+const mapStateToProps = state => {
+  return {
+    adbAddonStatus: state.ui.adbAddonStatus,
+    isAdbReady: state.ui.isAdbReady,
+    isScanningUsb: state.ui.isScanningUsb,
+    networkLocations: state.ui.networkLocations,
+    networkRuntimes: state.runtimes.networkRuntimes,
+    selectedPage: state.ui.selectedPage,
+    selectedRuntimeId: state.runtimes.selectedRuntimeId,
+    usbRuntimes: state.runtimes.usbRuntimes,
+  };
+};
+
+const mapDispatchToProps = dispatch => ({
+  dispatch,
+});
+
+module.exports = FluentReact.withLocalization(
+  connect(mapStateToProps, mapDispatchToProps)(App)
+);
diff --git a/devtools/client/aboutdebugging/src/components/CompatibilityWarning.js b/devtools/client/aboutdebugging/src/components/CompatibilityWarning.js
new file mode 100644
index 0000000000..42284fa672
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/CompatibilityWarning.js
@@ -0,0 +1,110 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Message = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/Message.js")
+);
+
+const {
+  MESSAGE_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const {
+  COMPATIBILITY_STATUS,
+} = require("resource://devtools/client/shared/remote-debugging/version-checker.js");
+
+const TROUBLESHOOTING_URL =
+  "https://firefox-source-docs.mozilla.org/devtools-user/about_colon_debugging/";
+const FENNEC_TROUBLESHOOTING_URL =
+  "https://firefox-source-docs.mozilla.org/devtools-user/about_colon_debugging/index.html#connection-to-firefox-for-android-68";
+
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+class CompatibilityWarning extends PureComponent {
+  static get propTypes() {
+    return {
+      compatibilityReport: Types.compatibilityReport.isRequired,
+    };
+  }
+
+  render() {
+    const {
+      localID,
+      localVersion,
+      minVersion,
+      runtimeID,
+      runtimeVersion,
+      status,
+    } = this.props.compatibilityReport;
+
+    if (status === COMPATIBILITY_STATUS.COMPATIBLE) {
+      return null;
+    }
+
+    let localizationId, statusClassName;
+    switch (status) {
+      case COMPATIBILITY_STATUS.TOO_OLD:
+        statusClassName = "qa-compatibility-warning-too-old";
+        localizationId = "about-debugging-browser-version-too-old";
+        break;
+      case COMPATIBILITY_STATUS.TOO_RECENT:
+        statusClassName = "qa-compatibility-warning-too-recent";
+        localizationId = "about-debugging-browser-version-too-recent";
+        break;
+      case COMPATIBILITY_STATUS.TOO_OLD_FENNEC:
+        statusClassName = "qa-compatibility-warning-too-old-fennec";
+        localizationId = "about-debugging-browser-version-too-old-fennec";
+        break;
+    }
+
+    const troubleshootingUrl =
+      status === COMPATIBILITY_STATUS.TOO_OLD_FENNEC
+        ? FENNEC_TROUBLESHOOTING_URL
+        : TROUBLESHOOTING_URL;
+
+    const messageLevel =
+      status === COMPATIBILITY_STATUS.TOO_OLD_FENNEC
+        ? MESSAGE_LEVEL.ERROR
+        : MESSAGE_LEVEL.WARNING;
+
+    return Message(
+      {
+        level: messageLevel,
+        isCloseable: true,
+      },
+      Localized(
+        {
+          id: localizationId,
+          a: dom.a({
+            href: troubleshootingUrl,
+            target: "_blank",
+          }),
+          $localID: localID,
+          $localVersion: localVersion,
+          $minVersion: minVersion,
+          $runtimeID: runtimeID,
+          $runtimeVersion: runtimeVersion,
+        },
+        dom.p(
+          {
+            className: `qa-compatibility-warning ${statusClassName}`,
+          },
+          localizationId
+        )
+      )
+    );
+  }
+}
+
+module.exports = CompatibilityWarning;
diff --git a/devtools/client/aboutdebugging/src/components/ConnectionPromptSetting.js b/devtools/client/aboutdebugging/src/components/ConnectionPromptSetting.js
new file mode 100644
index 0000000000..d4773bb298
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/ConnectionPromptSetting.js
@@ -0,0 +1,55 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+
+class ConnectionPromptSetting extends PureComponent {
+  static get propTypes() {
+    return {
+      className: PropTypes.string,
+      connectionPromptEnabled: PropTypes.bool.isRequired,
+      dispatch: PropTypes.func.isRequired,
+    };
+  }
+
+  onToggleClick() {
+    const { connectionPromptEnabled, dispatch } = this.props;
+    dispatch(Actions.updateConnectionPromptSetting(!connectionPromptEnabled));
+  }
+
+  render() {
+    const { className, connectionPromptEnabled } = this.props;
+
+    const localizedState = connectionPromptEnabled
+      ? "about-debugging-connection-prompt-disable-button"
+      : "about-debugging-connection-prompt-enable-button";
+
+    return Localized(
+      {
+        id: localizedState,
+      },
+      dom.button(
+        {
+          className: `${className} default-button qa-connection-prompt-toggle-button`,
+          onClick: () => this.onToggleClick(),
+        },
+        localizedState
+      )
+    );
+  }
+}
+
+module.exports = ConnectionPromptSetting;
diff --git a/devtools/client/aboutdebugging/src/components/ProfilerDialog.css b/devtools/client/aboutdebugging/src/components/ProfilerDialog.css
new file mode 100644
index 0000000000..d5352bbea2
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/ProfilerDialog.css
@@ -0,0 +1,63 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.profiler-dialog__frame {
+  border: none;
+  height: 100%;
+  width: 100%;
+}
+
+/*
+ * The current layout of the dialog header is
+ *
+ *  +-----------------------------+---+
+ *  | dialog title (auto)         | X |
+ *  +-----------------------------+---+
+ */
+.profiler-dialog__header {
+  align-items: center;
+  background-color: var(--popup-header-background-color);
+  color: var(--popup-header-color);
+  display: grid;
+  grid-template-columns: 1fr max-content;
+  padding: var(--base-unit);
+}
+
+.profiler-dialog__header__title {
+  margin-inline-start: calc(var(--base-unit) * 2);
+
+  /* Reset <h1> styles */
+  font-size: 15px;
+  font-weight: normal;
+}
+
+.profiler-dialog__inner {
+  background-color: var(--box-background);
+  display: grid;
+  grid-template-rows: max-content auto;
+  max-height: calc(100% - calc(var(--base-unit) * 25)); /* 100% - 100px */
+  position: fixed;
+}
+
+.profiler-dialog__inner--medium {
+  width: calc(var(--base-unit) * 150); /* 600px */
+  height: calc(var(--base-unit) * 150); /* 600px */
+}
+
+.profiler-dialog__inner--large {
+  width: calc(var(--base-unit) * 200); /* 800px */
+  height: calc(var(--base-unit) * 175); /* 700px */
+}
+
+.profiler-dialog__mask {
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  background-color: var(--grey-90-a60);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
diff --git a/devtools/client/aboutdebugging/src/components/ProfilerDialog.js b/devtools/client/aboutdebugging/src/components/ProfilerDialog.js
new file mode 100644
index 0000000000..f4bb583464
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/ProfilerDialog.js
@@ -0,0 +1,168 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  connect,
+} = require("resource://devtools/client/shared/vendor/react-redux.js");
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+const {
+  PROFILER_PAGE_CONTEXT,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This component is a modal dialog containing the performance profiler UI. It uses
+ * the simplified DevTools panel located in devtools/client/performance-new. When
+ * using a custom preset, and editing the settings, the page context switches
+ * to about:profiling, which receives the PerfFront of the remote debuggee.
+ */
+class ProfilerDialog extends PureComponent {
+  static get propTypes() {
+    return {
+      runtimeDetails: Types.runtimeDetails.isRequired,
+      profilerContext: PropTypes.string.isRequired,
+      hideProfilerDialog: PropTypes.func.isRequired,
+      switchProfilerContext: PropTypes.func.isRequired,
+    };
+  }
+
+  hide() {
+    this.props.hideProfilerDialog();
+  }
+
+  setProfilerIframeDirection(frameWindow) {
+    // Set iframe direction according to the parent document direction.
+    const { documentElement } = document;
+    const dir = window.getComputedStyle(documentElement).direction;
+    frameWindow.document.documentElement.setAttribute("dir", dir);
+  }
+
+  /**
+   * The profiler iframe can either be the simplified devtools recording panel,
+   * or the more detailed about:profiling settings page.
+   */
+  renderProfilerIframe() {
+    const {
+      runtimeDetails: { clientWrapper },
+      switchProfilerContext,
+      profilerContext,
+    } = this.props;
+
+    let src, onLoad;
+
+    switch (profilerContext) {
+      case PROFILER_PAGE_CONTEXT.DEVTOOLS_REMOTE:
+        src = clientWrapper.getPerformancePanelUrl();
+        onLoad = e => {
+          const frameWindow = e.target.contentWindow;
+          this.setProfilerIframeDirection(frameWindow);
+
+          clientWrapper.loadPerformanceProfiler(frameWindow, () => {
+            switchProfilerContext(PROFILER_PAGE_CONTEXT.ABOUTPROFILING_REMOTE);
+          });
+        };
+        break;
+
+      case PROFILER_PAGE_CONTEXT.ABOUTPROFILING_REMOTE:
+        src = "about:profiling#remote";
+        onLoad = e => {
+          const frameWindow = e.target.contentWindow;
+          this.setProfilerIframeDirection(frameWindow);
+
+          clientWrapper.loadAboutProfiling(frameWindow, () => {
+            switchProfilerContext(PROFILER_PAGE_CONTEXT.DEVTOOLS_REMOTE);
+          });
+        };
+        break;
+
+      default:
+        throw new Error(`Unhandled profiler context: "${profilerContext}"`);
+    }
+
+    return dom.iframe({
+      key: profilerContext,
+      className: "profiler-dialog__frame",
+      src,
+      onLoad,
+    });
+  }
+
+  render() {
+    const { profilerContext, switchProfilerContext } = this.props;
+    const dialogSizeClassName =
+      profilerContext === PROFILER_PAGE_CONTEXT.DEVTOOLS_REMOTE
+        ? "profiler-dialog__inner--medium"
+        : "profiler-dialog__inner--large";
+
+    return dom.div(
+      {
+        className: "profiler-dialog__mask qa-profiler-dialog-mask",
+        onClick: () => this.hide(),
+      },
+      dom.article(
+        {
+          className: `profiler-dialog__inner ${dialogSizeClassName} qa-profiler-dialog`,
+          onClick: e => e.stopPropagation(),
+        },
+        dom.header(
+          {
+            className: "profiler-dialog__header",
+          },
+          Localized(
+            {
+              id: "about-debugging-profiler-dialog-title2",
+            },
+            dom.h1(
+              {
+                className: "profiler-dialog__header__title",
+              },
+              "about-debugging-profiler-dialog-title2"
+            )
+          ),
+          dom.button(
+            {
+              className: "ghost-button qa-profiler-dialog-close",
+              onClick: () => {
+                if (profilerContext === PROFILER_PAGE_CONTEXT.DEVTOOLS_REMOTE) {
+                  this.hide();
+                } else {
+                  switchProfilerContext(PROFILER_PAGE_CONTEXT.DEVTOOLS_REMOTE);
+                }
+              },
+            },
+            dom.img({
+              src: "chrome://devtools/skin/images/close.svg",
+            })
+          )
+        ),
+        this.renderProfilerIframe()
+      )
+    );
+  }
+}
+
+const mapStateToProps = state => {
+  return {
+    profilerContext: state.ui.profilerContext,
+  };
+};
+
+const mapDispatchToProps = {
+  hideProfilerDialog: Actions.hideProfilerDialog,
+  switchProfilerContext: Actions.switchProfilerContext,
+};
+
+module.exports = connect(mapStateToProps, mapDispatchToProps)(ProfilerDialog);
diff --git a/devtools/client/aboutdebugging/src/components/RuntimeActions.css b/devtools/client/aboutdebugging/src/components/RuntimeActions.css
new file mode 100644
index 0000000000..6333560d4b
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/RuntimeActions.css
@@ -0,0 +1,9 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.runtime-actions__toolbar {
+  column-gap: var(--base-unit);
+  display: flex;
+  justify-content: end;
+}
diff --git a/devtools/client/aboutdebugging/src/components/RuntimeActions.js b/devtools/client/aboutdebugging/src/components/RuntimeActions.js
new file mode 100644
index 0000000000..eefa8b500b
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/RuntimeActions.js
@@ -0,0 +1,82 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const ConnectionPromptSetting = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/ConnectionPromptSetting.js")
+);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const {
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+class RuntimeActions extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      runtimeDetails: Types.runtimeDetails,
+      runtimeId: PropTypes.string.isRequired,
+    };
+  }
+
+  onProfilerButtonClick() {
+    this.props.dispatch(Actions.showProfilerDialog());
+  }
+
+  renderConnectionPromptSetting() {
+    const { dispatch, runtimeDetails, runtimeId } = this.props;
+    const { connectionPromptEnabled } = runtimeDetails;
+    // do not show the connection prompt setting in 'This Firefox'
+    return runtimeId !== RUNTIMES.THIS_FIREFOX
+      ? ConnectionPromptSetting({
+          connectionPromptEnabled,
+          dispatch,
+        })
+      : null;
+  }
+
+  renderProfileButton() {
+    const { runtimeId } = this.props;
+
+    return runtimeId !== RUNTIMES.THIS_FIREFOX
+      ? Localized(
+          {
+            id: "about-debugging-runtime-profile-button2",
+          },
+          dom.button(
+            {
+              className: "default-button qa-profile-runtime-button",
+              onClick: () => this.onProfilerButtonClick(),
+            },
+            "about-debugging-runtime-profile-button2"
+          )
+        )
+      : null;
+  }
+
+  render() {
+    return dom.div(
+      {
+        className: "runtime-actions__toolbar",
+      },
+      this.renderProfileButton(),
+      this.renderConnectionPromptSetting()
+    );
+  }
+}
+
+module.exports = RuntimeActions;
diff --git a/devtools/client/aboutdebugging/src/components/RuntimeInfo.css b/devtools/client/aboutdebugging/src/components/RuntimeInfo.css
new file mode 100644
index 0000000000..e6fcd9dd7e
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/RuntimeInfo.css
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+/**
+ * Layout for the runtime info container is:
+ *
+ *      <- 68px --x--------- 1fr ----------><---- max ---->
+ *   ∧  +---------+------------------------+--------------+
+ *  1fr |         | Runtime Info           |   [Action]   |
+ *   |  |  Icon   | eg "Firefox (70.0a1)"  |              |
+ *   x  |         +------------------------+              |
+ *  max |         | Device Name (optional) |              |
+ *   ∨  +---------+------------------------+--------------+
+ */
+.runtime-info {
+  align-items: center;
+  display: grid;
+
+  grid-column-gap: var(--main-heading-icon-gap);
+  grid-template-areas:
+  "icon title    action"
+  "icon subtitle .";
+  grid-template-columns: var(--main-heading-icon-size) 1fr max-content;
+  grid-template-rows: 1fr max-content;
+
+  margin-block-end: calc(var(--base-unit) * 5);
+}
+
+.runtime-info__icon {
+  grid-area: icon;
+}
+.runtime-info__title {
+  grid-area: title;
+}
+.runtime-info__subtitle {
+  grid-area: subtitle;
+}
+.runtime-info__action {
+  grid-area: action;
+}
diff --git a/devtools/client/aboutdebugging/src/components/RuntimeInfo.js b/devtools/client/aboutdebugging/src/components/RuntimeInfo.js
new file mode 100644
index 0000000000..6a8c67dd33
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/RuntimeInfo.js
@@ -0,0 +1,89 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This component displays runtime information.
+ */
+class RuntimeInfo extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      icon: PropTypes.string.isRequired,
+      deviceName: PropTypes.string,
+      name: PropTypes.string.isRequired,
+      version: PropTypes.string.isRequired,
+      runtimeId: PropTypes.string.isRequired,
+    };
+  }
+  render() {
+    const { icon, deviceName, name, version, runtimeId, dispatch } = this.props;
+
+    return dom.h1(
+      {
+        className: "main-heading runtime-info",
+      },
+      dom.img({
+        className: "main-heading__icon runtime-info__icon qa-runtime-icon",
+        src: icon,
+      }),
+      Localized(
+        {
+          id: "about-debugging-runtime-name",
+          $name: name,
+          $version: version,
+        },
+        dom.label(
+          {
+            className: "qa-runtime-name runtime-info__title",
+          },
+          `${name} (${version})`
+        )
+      ),
+      deviceName
+        ? dom.label(
+            {
+              className: "main-heading-subtitle runtime-info__subtitle",
+            },
+            deviceName
+          )
+        : null,
+      runtimeId !== RUNTIMES.THIS_FIREFOX
+        ? Localized(
+            {
+              id: "about-debugging-runtime-disconnect-button",
+            },
+            dom.button(
+              {
+                className:
+                  "default-button runtime-info__action qa-runtime-info__action",
+                onClick() {
+                  dispatch(Actions.disconnectRuntime(runtimeId, true));
+                },
+              },
+              "Disconnect"
+            )
+          )
+        : null
+    );
+  }
+}
+
+module.exports = RuntimeInfo;
diff --git a/devtools/client/aboutdebugging/src/components/RuntimePage.js b/devtools/client/aboutdebugging/src/components/RuntimePage.js
new file mode 100644
index 0000000000..e2dae9b0cd
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/RuntimePage.js
@@ -0,0 +1,306 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  connect,
+} = require("resource://devtools/client/shared/vendor/react-redux.js");
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const CompatibilityWarning = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/CompatibilityWarning.js")
+);
+const DebugTargetPane = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetPane.js")
+);
+const ExtensionDetail = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/ExtensionDetail.js")
+);
+const InspectAction = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/InspectAction.js")
+);
+const ProfilerDialog = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/ProfilerDialog.js")
+);
+const RuntimeActions = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/RuntimeActions.js")
+);
+const RuntimeInfo = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/RuntimeInfo.js")
+);
+const ServiceWorkerAction = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAction.js")
+);
+const ServiceWorkerAdditionalActions = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAdditionalActions.js")
+);
+const ServiceWorkersWarning = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/ServiceWorkersWarning.js")
+);
+const ProcessDetail = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/ProcessDetail.js")
+);
+const TabAction = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/TabAction.js")
+);
+const TabDetail = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/TabDetail.js")
+);
+const TemporaryExtensionAdditionalActions = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionAdditionalActions.js")
+);
+const TemporaryExtensionDetail = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionDetail.js")
+);
+const TemporaryExtensionInstallSection = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstallSection.js")
+);
+const WorkerDetail = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/WorkerDetail.js")
+);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const {
+  DEBUG_TARGETS,
+  DEBUG_TARGET_PANE,
+  PAGE_TYPES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+const {
+  getCurrentRuntimeDetails,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js");
+const {
+  isSupportedDebugTargetPane,
+  supportsTemporaryExtensionInstaller,
+} = require("resource://devtools/client/aboutdebugging/src/modules/debug-target-support.js");
+
+class RuntimePage extends PureComponent {
+  static get propTypes() {
+    return {
+      collapsibilities: Types.collapsibilities.isRequired,
+      dispatch: PropTypes.func.isRequired,
+      installedExtensions: PropTypes.arrayOf(PropTypes.object).isRequired,
+      otherWorkers: PropTypes.arrayOf(PropTypes.object).isRequired,
+      runtimeDetails: Types.runtimeDetails,
+      runtimeId: PropTypes.string.isRequired,
+      processes: PropTypes.arrayOf(PropTypes.object).isRequired,
+      serviceWorkers: PropTypes.arrayOf(PropTypes.object).isRequired,
+      sharedWorkers: PropTypes.arrayOf(PropTypes.object).isRequired,
+      showProfilerDialog: PropTypes.bool.isRequired,
+      tabs: PropTypes.arrayOf(PropTypes.object).isRequired,
+      temporaryExtensions: PropTypes.arrayOf(PropTypes.object).isRequired,
+      temporaryInstallError: PropTypes.object,
+    };
+  }
+
+  // TODO: avoid the use of this method
+  // https://bugzilla.mozilla.org/show_bug.cgi?id=1774507
+  UNSAFE_componentWillMount() {
+    const { dispatch, runtimeId } = this.props;
+    dispatch(Actions.selectPage(PAGE_TYPES.RUNTIME, runtimeId));
+  }
+
+  getIconByType(type) {
+    switch (type) {
+      case DEBUG_TARGETS.EXTENSION:
+        return "chrome://devtools/skin/images/debugging-addons.svg";
+      case DEBUG_TARGETS.PROCESS:
+        return "chrome://devtools/skin/images/aboutdebugging-process-icon.svg";
+      case DEBUG_TARGETS.TAB:
+        return "chrome://devtools/skin/images/debugging-tabs.svg";
+      case DEBUG_TARGETS.WORKER:
+        return "chrome://devtools/skin/images/debugging-workers.svg";
+    }
+
+    throw new Error(`Unsupported type [${type}]`);
+  }
+
+  renderDebugTargetPane({
+    actionComponent,
+    additionalActionsComponent,
+    children,
+    detailComponent,
+    icon,
+    localizationId,
+    name,
+    paneKey,
+    targets,
+  }) {
+    const { collapsibilities, dispatch, runtimeDetails } = this.props;
+
+    if (!isSupportedDebugTargetPane(runtimeDetails.info.type, paneKey)) {
+      return null;
+    }
+
+    return Localized(
+      {
+        id: localizationId,
+        attrs: { name: true },
+      },
+      DebugTargetPane(
+        {
+          actionComponent,
+          additionalActionsComponent,
+          collapsibilityKey: paneKey,
+          detailComponent,
+          dispatch,
+          icon,
+          isCollapsed: collapsibilities.get(paneKey),
+          name,
+          targets,
+        },
+        children
+      )
+    );
+  }
+
+  renderTemporaryExtensionInstallSection() {
+    const runtimeType = this.props.runtimeDetails.info.type;
+    if (
+      !isSupportedDebugTargetPane(
+        runtimeType,
+        DEBUG_TARGET_PANE.TEMPORARY_EXTENSION
+      ) ||
+      !supportsTemporaryExtensionInstaller(runtimeType)
+    ) {
+      return null;
+    }
+
+    const { dispatch, temporaryInstallError } = this.props;
+    return TemporaryExtensionInstallSection({
+      dispatch,
+      temporaryInstallError,
+    });
+  }
+
+  render() {
+    const {
+      dispatch,
+      installedExtensions,
+      otherWorkers,
+      processes,
+      runtimeDetails,
+      runtimeId,
+      serviceWorkers,
+      sharedWorkers,
+      showProfilerDialog,
+      tabs,
+      temporaryExtensions,
+    } = this.props;
+
+    if (!runtimeDetails) {
+      // runtimeInfo can be null when the selectPage action navigates from a runtime A
+      // to a runtime B (between unwatchRuntime and watchRuntime).
+      return null;
+    }
+
+    const { compatibilityReport } = runtimeDetails;
+
+    return dom.article(
+      {
+        className: "page qa-runtime-page",
+      },
+      RuntimeInfo({ ...runtimeDetails.info, runtimeId, dispatch }),
+      RuntimeActions({ dispatch, runtimeId, runtimeDetails }),
+      runtimeDetails.serviceWorkersAvailable ? null : ServiceWorkersWarning(),
+      CompatibilityWarning({ compatibilityReport }),
+      this.renderDebugTargetPane({
+        actionComponent: TabAction,
+        detailComponent: TabDetail,
+        icon: this.getIconByType(DEBUG_TARGETS.TAB),
+        localizationId: "about-debugging-runtime-tabs",
+        name: "Tabs",
+        paneKey: DEBUG_TARGET_PANE.TAB,
+        targets: tabs,
+      }),
+      this.renderDebugTargetPane({
+        actionComponent: InspectAction,
+        additionalActionsComponent: TemporaryExtensionAdditionalActions,
+        children: this.renderTemporaryExtensionInstallSection(),
+        detailComponent: TemporaryExtensionDetail,
+        icon: this.getIconByType(DEBUG_TARGETS.EXTENSION),
+        localizationId: "about-debugging-runtime-temporary-extensions",
+        name: "Temporary Extensions",
+        paneKey: DEBUG_TARGET_PANE.TEMPORARY_EXTENSION,
+        targets: temporaryExtensions,
+      }),
+      this.renderDebugTargetPane({
+        actionComponent: InspectAction,
+        detailComponent: ExtensionDetail,
+        icon: this.getIconByType(DEBUG_TARGETS.EXTENSION),
+        localizationId: "about-debugging-runtime-extensions",
+        name: "Extensions",
+        paneKey: DEBUG_TARGET_PANE.INSTALLED_EXTENSION,
+        targets: installedExtensions,
+      }),
+      this.renderDebugTargetPane({
+        actionComponent: ServiceWorkerAction,
+        additionalActionsComponent: ServiceWorkerAdditionalActions,
+        detailComponent: WorkerDetail,
+        icon: this.getIconByType(DEBUG_TARGETS.WORKER),
+        localizationId: "about-debugging-runtime-service-workers",
+        name: "Service Workers",
+        paneKey: DEBUG_TARGET_PANE.SERVICE_WORKER,
+        targets: serviceWorkers,
+      }),
+      this.renderDebugTargetPane({
+        actionComponent: InspectAction,
+        detailComponent: WorkerDetail,
+        icon: this.getIconByType(DEBUG_TARGETS.WORKER),
+        localizationId: "about-debugging-runtime-shared-workers",
+        name: "Shared Workers",
+        paneKey: DEBUG_TARGET_PANE.SHARED_WORKER,
+        targets: sharedWorkers,
+      }),
+      this.renderDebugTargetPane({
+        actionComponent: InspectAction,
+        detailComponent: WorkerDetail,
+        icon: this.getIconByType(DEBUG_TARGETS.WORKER),
+        localizationId: "about-debugging-runtime-other-workers",
+        name: "Other Workers",
+        paneKey: DEBUG_TARGET_PANE.OTHER_WORKER,
+        targets: otherWorkers,
+      }),
+      this.renderDebugTargetPane({
+        actionComponent: InspectAction,
+        detailComponent: ProcessDetail,
+        icon: this.getIconByType(DEBUG_TARGETS.PROCESS),
+        localizationId: "about-debugging-runtime-processes",
+        name: "Processes",
+        paneKey: DEBUG_TARGET_PANE.PROCESSES,
+        targets: processes,
+      }),
+
+      showProfilerDialog ? ProfilerDialog({ dispatch, runtimeDetails }) : null
+    );
+  }
+}
+
+const mapStateToProps = state => {
+  return {
+    collapsibilities: state.ui.debugTargetCollapsibilities,
+    installedExtensions: state.debugTargets.installedExtensions,
+    processes: state.debugTargets.processes,
+    otherWorkers: state.debugTargets.otherWorkers,
+    runtimeDetails: getCurrentRuntimeDetails(state.runtimes),
+    serviceWorkers: state.debugTargets.serviceWorkers,
+    sharedWorkers: state.debugTargets.sharedWorkers,
+    showProfilerDialog: state.ui.showProfilerDialog,
+    tabs: state.debugTargets.tabs,
+    temporaryExtensions: state.debugTargets.temporaryExtensions,
+    temporaryInstallError: state.ui.temporaryInstallError,
+  };
+};
+
+module.exports = connect(mapStateToProps)(RuntimePage);
diff --git a/devtools/client/aboutdebugging/src/components/ServiceWorkersWarning.js b/devtools/client/aboutdebugging/src/components/ServiceWorkersWarning.js
new file mode 100644
index 0000000000..4f9dc93d7f
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/ServiceWorkersWarning.js
@@ -0,0 +1,52 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Message = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/Message.js")
+);
+
+const {
+  MESSAGE_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const DOC_URL =
+  "https://firefox-source-docs.mozilla.org/devtools-user/about_colon_debugging/index.html#service-workers-not-compatible";
+
+class ServiceWorkersWarning extends PureComponent {
+  render() {
+    return Message(
+      {
+        level: MESSAGE_LEVEL.WARNING,
+        isCloseable: true,
+      },
+      Localized(
+        {
+          id: "about-debugging-runtime-service-workers-not-compatible",
+          a: dom.a({
+            href: DOC_URL,
+            target: "_blank",
+          }),
+        },
+        dom.p(
+          {
+            className: "qa-service-workers-warning",
+          },
+          "about-debugging-runtime-service-workers-not-compatible"
+        )
+      )
+    );
+  }
+}
+
+module.exports = ServiceWorkersWarning;
diff --git a/devtools/client/aboutdebugging/src/components/connect/ConnectPage.css b/devtools/client/aboutdebugging/src/components/connect/ConnectPage.css
new file mode 100644
index 0000000000..a693bf4113
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/ConnectPage.css
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.connect-page__breather {
+  margin-block-start: calc(var(--base-unit) * 6);
+}
+
+/*
+ *   +--------+----------------------+
+ *   | USB    |            |<button> |
+ *   +--------+            |         |
+ *   | status |            |         |
+ *   +--------+----------------------+
+ */
+.connect-page__usb-section__heading {
+  display: grid;
+  align-items: center;
+  grid-template-areas: "title  . toggle"
+                       "status . toggle";
+  grid-template-columns: auto 1fr auto;
+  grid-column-gap: calc(var(--base-unit) * 2);
+  grid-row-gap: var(--base-unit);
+}
+
+.connect-page__usb-section__heading__toggle {
+  grid-area: toggle;
+}
+
+.connect-page__usb-section__heading__title {
+  grid-area: title;
+  line-height: 1;
+}
+.connect-page__usb-section__heading__status {
+  grid-area: status;
+  line-height: 1;
+  font-size: var(--caption-20-font-size);
+  font-weight: var(--caption-20-font-weight);
+  color: var(--secondary-text-color);
+}
+
+.connect-page__troubleshoot {
+  font-size: var(--body-10-font-size);
+  font-weight: var(--body-10-font-weight);
+  margin-block-start: calc(var(--base-unit) * 2);
+}
+
+.connect-page__troubleshoot--network {
+  padding-inline: calc(var(--base-unit) * 6);
+}
diff --git a/devtools/client/aboutdebugging/src/components/connect/ConnectPage.js b/devtools/client/aboutdebugging/src/components/connect/ConnectPage.js
new file mode 100644
index 0000000000..97b1b01df7
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/ConnectPage.js
@@ -0,0 +1,315 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  USB_STATES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+
+loader.lazyRequireGetter(
+  this,
+  "ADB_ADDON_STATES",
+  "resource://devtools/client/shared/remote-debugging/adb/adb-addon.js",
+  true
+);
+
+const Link = createFactory(
+  require("resource://devtools/client/shared/vendor/react-router-dom.js").Link
+);
+const ConnectSection = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/connect/ConnectSection.js")
+);
+const ConnectSteps = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/connect/ConnectSteps.js")
+);
+const NetworkLocationsForm = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/connect/NetworkLocationsForm.js")
+);
+const NetworkLocationsList = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/connect/NetworkLocationsList.js")
+);
+
+const {
+  PAGE_TYPES,
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+const USB_ICON_SRC =
+  "chrome://devtools/skin/images/aboutdebugging-usb-icon.svg";
+const GLOBE_ICON_SRC =
+  "chrome://devtools/skin/images/aboutdebugging-globe-icon.svg";
+
+const TROUBLESHOOT_USB_URL =
+  "https://firefox-source-docs.mozilla.org/devtools-user/about_colon_debugging/index.html#connecting-to-a-remote-device";
+const TROUBLESHOOT_NETWORK_URL =
+  "https://firefox-source-docs.mozilla.org/devtools-user/about_colon_debugging/index.html#connecting-over-the-network";
+
+class ConnectPage extends PureComponent {
+  static get propTypes() {
+    return {
+      adbAddonStatus: Types.adbAddonStatus,
+      dispatch: PropTypes.func.isRequired,
+      networkLocations: PropTypes.arrayOf(Types.location).isRequired,
+    };
+  }
+
+  // TODO: avoid the use of this method
+  // https://bugzilla.mozilla.org/show_bug.cgi?id=1774507
+  UNSAFE_componentWillMount() {
+    this.props.dispatch(Actions.selectPage(PAGE_TYPES.CONNECT));
+  }
+
+  onToggleUSBClick() {
+    const { adbAddonStatus } = this.props;
+    const isAddonInstalled = adbAddonStatus === ADB_ADDON_STATES.INSTALLED;
+    if (isAddonInstalled) {
+      this.props.dispatch(Actions.uninstallAdbAddon());
+    } else {
+      this.props.dispatch(Actions.installAdbAddon());
+    }
+  }
+
+  getUsbStatus() {
+    switch (this.props.adbAddonStatus) {
+      case ADB_ADDON_STATES.INSTALLED:
+        return USB_STATES.ENABLED_USB;
+      case ADB_ADDON_STATES.UNINSTALLED:
+        return USB_STATES.DISABLED_USB;
+      default:
+        return USB_STATES.UPDATING_USB;
+    }
+  }
+
+  renderUsbStatus() {
+    const statusTextId = {
+      [USB_STATES.ENABLED_USB]: "about-debugging-setup-usb-status-enabled",
+      [USB_STATES.DISABLED_USB]: "about-debugging-setup-usb-status-disabled",
+      [USB_STATES.UPDATING_USB]: "about-debugging-setup-usb-status-updating",
+    }[this.getUsbStatus()];
+
+    return Localized(
+      {
+        id: statusTextId,
+      },
+      dom.span(
+        {
+          className: "connect-page__usb-section__heading__status",
+        },
+        statusTextId
+      )
+    );
+  }
+
+  renderUsbToggleButton() {
+    const usbStatus = this.getUsbStatus();
+
+    const localizedStates = {
+      [USB_STATES.ENABLED_USB]: "about-debugging-setup-usb-disable-button",
+      [USB_STATES.DISABLED_USB]: "about-debugging-setup-usb-enable-button",
+      [USB_STATES.UPDATING_USB]: "about-debugging-setup-usb-updating-button",
+    };
+    const localizedState = localizedStates[usbStatus];
+
+    // Disable the button while the USB status is updating.
+    const disabled = usbStatus === USB_STATES.UPDATING_USB;
+
+    return Localized(
+      {
+        id: localizedState,
+      },
+      dom.button(
+        {
+          className:
+            "default-button connect-page__usb-section__heading__toggle " +
+            "qa-connect-usb-toggle-button",
+          disabled,
+          onClick: () => this.onToggleUSBClick(),
+        },
+        localizedState
+      )
+    );
+  }
+
+  renderUsb() {
+    const { adbAddonStatus } = this.props;
+    const isAddonInstalled = adbAddonStatus === ADB_ADDON_STATES.INSTALLED;
+    return ConnectSection(
+      {
+        icon: USB_ICON_SRC,
+        title: dom.div(
+          {
+            className: "connect-page__usb-section__heading",
+          },
+          Localized(
+            { id: "about-debugging-setup-usb-title" },
+            dom.span(
+              {
+                className: "connect-page__usb-section__heading__title",
+              },
+              "USB"
+            )
+          ),
+          this.renderUsbStatus(),
+          this.renderUsbToggleButton()
+        ),
+      },
+      isAddonInstalled
+        ? ConnectSteps({
+            steps: [
+              {
+                localizationId:
+                  "about-debugging-setup-usb-step-enable-dev-menu2",
+              },
+              {
+                localizationId: "about-debugging-setup-usb-step-enable-debug2",
+              },
+              {
+                localizationId:
+                  "about-debugging-setup-usb-step-enable-debug-firefox2",
+              },
+              {
+                localizationId: "about-debugging-setup-usb-step-plug-device",
+              },
+            ],
+          })
+        : Localized(
+            {
+              id: "about-debugging-setup-usb-disabled",
+            },
+            dom.aside(
+              {
+                className: "qa-connect-usb-disabled-message",
+              },
+              "Enabling this will download and add the required Android USB debugging " +
+                "components to Firefox."
+            )
+          ),
+      this.renderTroubleshootText(RUNTIMES.USB)
+    );
+  }
+
+  renderNetwork() {
+    const { dispatch, networkLocations } = this.props;
+
+    return Localized(
+      {
+        id: "about-debugging-setup-network",
+        attrs: { title: true },
+      },
+      ConnectSection({
+        icon: GLOBE_ICON_SRC,
+        title: "Network Location",
+        extraContent: dom.div(
+          {},
+          NetworkLocationsList({ dispatch, networkLocations }),
+          NetworkLocationsForm({ dispatch, networkLocations }),
+          this.renderTroubleshootText(RUNTIMES.NETWORK)
+        ),
+      })
+    );
+  }
+
+  renderTroubleshootText(connectionType) {
+    const localizationId =
+      connectionType === RUNTIMES.USB
+        ? "about-debugging-setup-usb-troubleshoot"
+        : "about-debugging-setup-network-troubleshoot";
+
+    const className =
+      "connect-page__troubleshoot connect-page__troubleshoot--" +
+      `${connectionType === RUNTIMES.USB ? "usb" : "network"}`;
+
+    const url =
+      connectionType === RUNTIMES.USB
+        ? TROUBLESHOOT_USB_URL
+        : TROUBLESHOOT_NETWORK_URL;
+
+    return dom.aside(
+      {
+        className,
+      },
+      Localized(
+        {
+          id: localizationId,
+          a: dom.a({
+            href: url,
+            target: "_blank",
+          }),
+        },
+        dom.p({}, localizationId)
+      )
+    );
+  }
+
+  render() {
+    return dom.article(
+      {
+        className: "page connect-page qa-connect-page",
+      },
+      Localized(
+        {
+          id: "about-debugging-setup-title",
+        },
+        dom.h1(
+          {
+            className: "alt-heading alt-heading--larger",
+          },
+          "Setup"
+        )
+      ),
+      Localized(
+        {
+          id: "about-debugging-setup-intro",
+        },
+        dom.p(
+          {},
+          "Configure the connection method you wish to remotely debug your device with."
+        )
+      ),
+      Localized(
+        {
+          id: "about-debugging-setup-this-firefox2",
+          a: Link({
+            to: `/runtime/${RUNTIMES.THIS_FIREFOX}`,
+          }),
+        },
+        dom.p({}, "about-debugging-setup-this-firefox")
+      ),
+      dom.section(
+        {
+          className: "connect-page__breather",
+        },
+        Localized(
+          {
+            id: "about-debugging-setup-connect-heading",
+          },
+          dom.h2(
+            {
+              className: "alt-heading",
+            },
+            "Connect a device"
+          )
+        ),
+        this.renderUsb(),
+        this.renderNetwork()
+      )
+    );
+  }
+}
+
+module.exports = FluentReact.withLocalization(ConnectPage);
diff --git a/devtools/client/aboutdebugging/src/components/connect/ConnectSection.css b/devtools/client/aboutdebugging/src/components/connect/ConnectSection.css
new file mode 100644
index 0000000000..4349b147b0
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/ConnectSection.css
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.connect-section {
+  --icon-size: calc(var(--base-unit) * 9);
+  --header-col-gap: calc(var(--base-unit) * 2);
+  margin-block-end: calc(var(--base-unit) * 4);
+}
+
+/*
+ *  +--------+----------------+
+ *  | <icon> |  <heading> 1fr |
+ *  +--------+----------------+
+ */
+.connect-section__header {
+  display: grid;
+  grid-template-areas: "icon heading";
+  grid-template-columns: auto 1fr;
+  grid-template-rows: var(--icon-size);
+  grid-column-gap: var(--header-col-gap);
+  align-items: center;
+
+  padding-block-end: calc(var(--base-unit) * 4);
+  padding-inline: calc(var(--base-unit) * 5);
+}
+
+.connect-section__header__title {
+  grid-area: heading;
+}
+
+.connect-section__header__icon {
+  grid-area: icon;
+  width: var(--icon-size);
+  height: var(--icon-size);
+
+  -moz-context-properties: fill;
+  fill: currentColor;
+}
+
+.connect-section__content {
+  line-height: 1.5;
+  padding-inline-start: calc(var(--base-unit) * 5
+    + var(--header-col-gap) + var(--icon-size));
+  padding-inline-end: calc(var(--base-unit) * 5);
+}
+
+.connect-section__extra {
+  border-block-start: 1px solid var(--card-separator-color);
+}
diff --git a/devtools/client/aboutdebugging/src/components/connect/ConnectSection.js b/devtools/client/aboutdebugging/src/components/connect/ConnectSection.js
new file mode 100644
index 0000000000..55f8eb4e78
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/ConnectSection.js
@@ -0,0 +1,69 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+class ConnectSection extends PureComponent {
+  static get propTypes() {
+    return {
+      children: PropTypes.node,
+      className: PropTypes.string,
+      extraContent: PropTypes.node,
+      icon: PropTypes.string.isRequired,
+      title: PropTypes.node.isRequired,
+    };
+  }
+
+  renderExtraContent() {
+    const { extraContent } = this.props;
+    return dom.section(
+      {
+        className: "connect-section__extra",
+      },
+      extraContent
+    );
+  }
+
+  render() {
+    const { extraContent } = this.props;
+
+    return dom.section(
+      {
+        className: `card connect-section ${this.props.className || ""}`,
+      },
+      dom.header(
+        {
+          className: "connect-section__header",
+        },
+        dom.img({
+          className: "connect-section__header__icon",
+          src: this.props.icon,
+        }),
+        dom.h1(
+          {
+            className: "card__heading connect-section__header__title",
+          },
+          this.props.title
+        )
+      ),
+      this.props.children
+        ? dom.div(
+            {
+              className: "connect-section__content",
+            },
+            this.props.children
+          )
+        : null,
+      extraContent ? this.renderExtraContent() : null
+    );
+  }
+}
+
+module.exports = ConnectSection;
diff --git a/devtools/client/aboutdebugging/src/components/connect/ConnectSteps.css b/devtools/client/aboutdebugging/src/components/connect/ConnectSteps.css
new file mode 100644
index 0000000000..bddd513aa7
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/ConnectSteps.css
@@ -0,0 +1,13 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.connect-page__step-list {
+  list-style-type: decimal;
+  list-style-position: outside;
+  margin-inline-start: calc(var(--base-unit) * 4);
+}
+
+.connect-page__step {
+  padding-inline-start: var(--base-unit);
+}
diff --git a/devtools/client/aboutdebugging/src/components/connect/ConnectSteps.js b/devtools/client/aboutdebugging/src/components/connect/ConnectSteps.js
new file mode 100644
index 0000000000..0e8d304108
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/ConnectSteps.js
@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  PureComponent,
+  createFactory,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+class ConnectSteps extends PureComponent {
+  static get propTypes() {
+    return {
+      steps: PropTypes.arrayOf(
+        PropTypes.shape({
+          localizationId: PropTypes.string.isRequired,
+        }).isRequired
+      ),
+    };
+  }
+
+  render() {
+    return dom.ul(
+      {
+        className: "connect-page__step-list",
+      },
+      ...this.props.steps.map(step =>
+        Localized(
+          {
+            id: step.localizationId,
+          },
+          dom.li(
+            {
+              className: "connect-page__step",
+              key: step.localizationId,
+            },
+            step.localizationId
+          )
+        )
+      )
+    );
+  }
+}
+
+module.exports = ConnectSteps;
diff --git a/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsForm.css b/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsForm.css
new file mode 100644
index 0000000000..5694bcf216
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsForm.css
@@ -0,0 +1,23 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Layout of a network location form
+ *
+ *  +-------------+--------------------+------------+
+ *  | "Host:port" | Input              | Add button |
+ *  +-------------+--------------------+------------+
+ */
+.connect-page__network-form {
+  display: grid;
+  grid-column-gap: calc(var(--base-unit) * 2);
+  grid-template-columns: auto 1fr auto;
+  align-items: center;
+  padding-block-start: calc(var(--base-unit) * 4);
+  padding-inline: calc(var(--base-unit) * 6);
+}
+
+.connect-page__network-form__error-message {
+  grid-column: 1 / -1;
+}
diff --git a/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsForm.js b/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsForm.js
new file mode 100644
index 0000000000..347167921b
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsForm.js
@@ -0,0 +1,148 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Message = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/Message.js")
+);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const {
+  MESSAGE_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+class NetworkLocationsForm extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      networkLocations: PropTypes.arrayOf(Types.location).isRequired,
+    };
+  }
+
+  constructor(props) {
+    super(props);
+    this.state = {
+      errorHostValue: null,
+      errorMessageId: null,
+      value: "",
+    };
+  }
+
+  onSubmit(e) {
+    const { networkLocations } = this.props;
+    const { value } = this.state;
+
+    e.preventDefault();
+
+    if (!value) {
+      return;
+    }
+
+    if (!value.match(/[^:]+:\d+/)) {
+      this.setState({
+        errorHostValue: value,
+        errorMessageId: "about-debugging-network-location-form-invalid",
+      });
+      return;
+    }
+
+    if (networkLocations.includes(value)) {
+      this.setState({
+        errorHostValue: value,
+        errorMessageId: "about-debugging-network-location-form-duplicate",
+      });
+      return;
+    }
+
+    this.props.dispatch(Actions.addNetworkLocation(value));
+    this.setState({ errorHostValue: null, errorMessageId: null, value: "" });
+  }
+
+  renderError() {
+    const { errorHostValue, errorMessageId } = this.state;
+
+    if (!errorMessageId) {
+      return null;
+    }
+
+    return Message(
+      {
+        className:
+          "connect-page__network-form__error-message " +
+          "qa-connect-page__network-form__error-message",
+        level: MESSAGE_LEVEL.ERROR,
+        isCloseable: true,
+      },
+      Localized(
+        {
+          id: errorMessageId,
+          "$host-value": errorHostValue,
+        },
+        dom.p(
+          {
+            className: "technical-text",
+          },
+          errorMessageId
+        )
+      )
+    );
+  }
+
+  render() {
+    return dom.form(
+      {
+        className: "connect-page__network-form",
+        onSubmit: e => this.onSubmit(e),
+      },
+      this.renderError(),
+      Localized(
+        {
+          id: "about-debugging-network-locations-host-input-label",
+        },
+        dom.label(
+          {
+            htmlFor: "about-debugging-network-locations-host-input",
+          },
+          "Host"
+        )
+      ),
+      dom.input({
+        id: "about-debugging-network-locations-host-input",
+        className: "default-input qa-network-form-input",
+        placeholder: "localhost:6080",
+        type: "text",
+        value: this.state.value,
+        onChange: e => {
+          const value = e.target.value;
+          this.setState({ value });
+        },
+      }),
+      Localized(
+        {
+          id: "about-debugging-network-locations-add-button",
+        },
+        dom.button(
+          {
+            className: "primary-button qa-network-form-submit-button",
+          },
+          "Add"
+        )
+      )
+    );
+  }
+}
+
+module.exports = NetworkLocationsForm;
diff --git a/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsList.css b/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsList.css
new file mode 100644
index 0000000000..e5676b784a
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsList.css
@@ -0,0 +1,20 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Layout of a network location item
+ *
+ *  +-------------------------------------+---------------+
+ *  | Location (eg localhost:8080)        | Remove button |
+ *  +-------------------------------------+---------------+
+ */
+.network-location {
+  display: grid;
+  grid-template-columns: auto max-content;
+  align-items: center;
+
+  padding-block: calc(var(--base-unit) * 2);
+  padding-inline: calc(var(--base-unit) * 6);
+  border-bottom: 1px solid var(--card-separator-color);
+}
diff --git a/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsList.js b/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsList.js
new file mode 100644
index 0000000000..e680fe525f
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/NetworkLocationsList.js
@@ -0,0 +1,67 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+class NetworkLocationsList extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      networkLocations: PropTypes.arrayOf(Types.location).isRequired,
+    };
+  }
+
+  renderList() {
+    return dom.ul(
+      {},
+      this.props.networkLocations.map(location =>
+        dom.li(
+          {
+            className: "network-location qa-network-location",
+            key: location,
+          },
+          dom.span(
+            {
+              className: "ellipsis-text qa-network-location-value",
+            },
+            location
+          ),
+          Localized(
+            {
+              id: "about-debugging-network-locations-remove-button",
+            },
+            dom.button(
+              {
+                className: "default-button qa-network-location-remove-button",
+                onClick: () => {
+                  this.props.dispatch(Actions.removeNetworkLocation(location));
+                },
+              },
+              "Remove"
+            )
+          )
+        )
+      )
+    );
+  }
+
+  render() {
+    return this.props.networkLocations.length ? this.renderList() : null;
+  }
+}
+
+module.exports = NetworkLocationsList;
diff --git a/devtools/client/aboutdebugging/src/components/connect/moz.build b/devtools/client/aboutdebugging/src/components/connect/moz.build
new file mode 100644
index 0000000000..9228e80125
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/connect/moz.build
@@ -0,0 +1,11 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "ConnectPage.js",
+    "ConnectSection.js",
+    "ConnectSteps.js",
+    "NetworkLocationsForm.js",
+    "NetworkLocationsList.js",
+)
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetItem.css b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetItem.css
new file mode 100644
index 0000000000..f049f33b23
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetItem.css
@@ -0,0 +1,97 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * The current layout of debug target item is
+ *
+ *  +--------+-----------------------------+----------------+
+ *  |        | Name                        |                |
+ *  | [Icon] |-----------------------------| Action button  |
+ *  |        | Subname                     |                |
+ *  +--------+-----------------------------+----------------+
+ *  | Detail                                                |
+ *  |                                                       |
+ *  +-------------------------------------------------------+
+ *  | Additional actions                                    |
+ *  |                                                       |
+ *  +-------------------------------------------------------+
+ */
+.debug-target-item {
+  display: grid;
+  grid-template-columns: calc(var(--base-unit) * 8) 1fr max-content;
+  grid-template-rows: 1fr minmax(0, auto) auto;
+  grid-column-gap: calc(var(--base-unit) * 2);
+  grid-template-areas: "icon               name               action"
+                       "icon               subname            action"
+                       "detail             detail             detail"
+                       "additional_actions additional_actions additional_actions";
+  margin-block-end: calc(var(--base-unit) * 4);
+
+  padding-block: calc(var(--base-unit) * 3) calc(var(--base-unit) * 2);
+  padding-inline: calc(var(--base-unit) * 3) calc(var(--base-unit) * 2);
+}
+
+.debug-target-item__icon {
+  align-self: center;
+  grid-area: icon;
+  margin-inline-start: calc(var(--base-unit) * 3);
+  width: 100%;
+
+  -moz-context-properties: fill;
+  fill: currentColor;
+}
+
+.debug-target-item__name {
+  align-self: center;
+  grid-area: name;
+  font-size: var(--body-20-font-size);
+  font-weight: var(--body-20-font-weight-bold);
+  line-height: 1.5;
+  margin-inline-start: calc(var(--base-unit) * 3);
+}
+
+.debug-target-item__action {
+  grid-area: action;
+  align-self: center;
+  margin-inline-end: calc(var(--base-unit) * 2);
+}
+
+.debug-target-item__additional_actions {
+  grid-area: additional_actions;
+  border-top: 1px solid var(--card-separator-color);
+  margin-block-start: calc(var(--base-unit) * 2);
+  padding-block-start: calc(var(--base-unit) * 2);
+  padding-inline-end: calc(var(--base-unit) * 2);
+}
+
+.debug-target-item__detail {
+  grid-area: detail;
+  margin-block-start: calc(var(--base-unit) * 3);
+}
+
+.debug-target-item__detail--empty {
+  margin-block-start: var(--base-unit);
+}
+
+.debug-target-item__messages {
+  margin-inline: calc(var(--base-unit) * 3) calc(var(--base-unit) * 2);
+}
+
+.debug-target-item__subname {
+  grid-area: subname;
+  color: var(--secondary-text-color);
+  font-size: var(--caption-20-font-size);
+  font-weight: var(--caption-20-font-weight);
+  line-height: 1.5;
+}
+
+/* The subname is always LTR under the Tabs section,
+   so check its parent's direction to set the correct margin. */
+.debug-target-item:dir(ltr) > .debug-target-item__subname {
+  margin-left: calc(var(--base-unit) * 3);
+}
+
+.debug-target-item:dir(rtl) > .debug-target-item__subname {
+  margin-right: calc(var(--base-unit) * 3);
+}
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetItem.js b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetItem.js
new file mode 100644
index 0000000000..6f19d7be02
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetItem.js
@@ -0,0 +1,91 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component displays debug target.
+ */
+class DebugTargetItem extends PureComponent {
+  static get propTypes() {
+    return {
+      actionComponent: PropTypes.any.isRequired,
+      additionalActionsComponent: PropTypes.any,
+      detailComponent: PropTypes.any.isRequired,
+      dispatch: PropTypes.func.isRequired,
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  renderAction() {
+    const { actionComponent, dispatch, target } = this.props;
+    return dom.div(
+      {
+        className: "debug-target-item__action",
+      },
+      actionComponent({ dispatch, target })
+    );
+  }
+
+  renderAdditionalActions() {
+    const { additionalActionsComponent, dispatch, target } = this.props;
+
+    if (!additionalActionsComponent) {
+      return null;
+    }
+
+    return dom.section(
+      {
+        className: "debug-target-item__additional_actions",
+      },
+      additionalActionsComponent({ dispatch, target })
+    );
+  }
+
+  renderDetail() {
+    const { detailComponent, target } = this.props;
+    return detailComponent({ target });
+  }
+
+  renderIcon() {
+    return dom.img({
+      className: "debug-target-item__icon qa-debug-target-item-icon",
+      src: this.props.target.icon,
+    });
+  }
+
+  renderName() {
+    return dom.span(
+      {
+        className: "debug-target-item__name ellipsis-text",
+        title: this.props.target.name,
+      },
+      this.props.target.name
+    );
+  }
+
+  render() {
+    return dom.li(
+      {
+        className: "card debug-target-item qa-debug-target-item",
+        "data-qa-target-type": this.props.target.type,
+      },
+      this.renderIcon(),
+      this.renderName(),
+      this.renderAction(),
+      this.renderDetail(),
+      this.renderAdditionalActions()
+    );
+  }
+}
+
+module.exports = DebugTargetItem;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetList.css b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetList.css
new file mode 100644
index 0000000000..827983e2bf
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetList.css
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.debug-target-list {
+  margin-block-start: calc(var(--base-unit) * 4);
+}
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetList.js b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetList.js
new file mode 100644
index 0000000000..ce1e7ff12c
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetList.js
@@ -0,0 +1,80 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const DebugTargetItem = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetItem.js")
+);
+
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component displays list of debug target.
+ */
+class DebugTargetList extends PureComponent {
+  static get propTypes() {
+    return {
+      actionComponent: PropTypes.any.isRequired,
+      additionalActionsComponent: PropTypes.any,
+      detailComponent: PropTypes.any.isRequired,
+      dispatch: PropTypes.func.isRequired,
+      targets: PropTypes.arrayOf(Types.debugTarget).isRequired,
+    };
+  }
+
+  renderEmptyList() {
+    return Localized(
+      {
+        id: "about-debugging-debug-target-list-empty",
+      },
+      dom.p(
+        {
+          className: "qa-debug-target-list-empty",
+        },
+        "Nothing yet."
+      )
+    );
+  }
+
+  render() {
+    const {
+      actionComponent,
+      additionalActionsComponent,
+      detailComponent,
+      dispatch,
+      targets,
+    } = this.props;
+
+    return targets.length === 0
+      ? this.renderEmptyList()
+      : dom.ul(
+          {
+            className: "debug-target-list qa-debug-target-list",
+          },
+          targets.map((target, key) =>
+            DebugTargetItem({
+              actionComponent,
+              additionalActionsComponent,
+              detailComponent,
+              dispatch,
+              key,
+              target,
+            })
+          )
+        );
+  }
+}
+
+module.exports = DebugTargetList;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetPane.css b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetPane.css
new file mode 100644
index 0000000000..616b4ac28c
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetPane.css
@@ -0,0 +1,43 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ *  Style for the heading of a debug target pane
+ *  +-----------------+---------------+-----------------+
+ *  | [Category icon] | Category name | [Collapse icon] |
+ *  +-----------------+---------------+-----------------+
+ */
+.debug-target-pane__heading {
+  grid-template-columns: var(--main-subheading-icon-size) max-content calc(var(--base-unit) * 3);
+  user-select: none;
+}
+
+.debug-target-pane__icon {
+  transition: transform 150ms cubic-bezier(.07, .95, 0, 1);
+  transform: rotate(90deg);
+}
+
+.debug-target-pane__icon--collapsed {
+  transform: rotate(0deg);
+}
+
+.debug-target-pane__icon--collapsed:dir(rtl) {
+  transform: rotate(180deg);
+}
+
+.debug-target-pane__title {
+  cursor: pointer;
+}
+
+.debug-target-pane__collapsable {
+  overflow: hidden;
+  /* padding will give space for card shadow to appear and
+     margin will correct the alignment */
+  margin-inline: calc(var(--card-shadow-blur-radius) * -1);
+  padding-inline: var(--card-shadow-blur-radius);
+}
+
+.debug-target-pane__collapsable--collapsed {
+  max-height: 0;
+}
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetPane.js b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetPane.js
new file mode 100644
index 0000000000..abfa1042b8
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetPane.js
@@ -0,0 +1,147 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  createRef,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+
+const DebugTargetList = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/DebugTargetList.js")
+);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component provides list for debug target and name area.
+ */
+class DebugTargetPane extends PureComponent {
+  static get propTypes() {
+    return {
+      actionComponent: PropTypes.any.isRequired,
+      additionalActionsComponent: PropTypes.any,
+      children: PropTypes.node,
+      collapsibilityKey: PropTypes.string.isRequired,
+      detailComponent: PropTypes.any.isRequired,
+      dispatch: PropTypes.func.isRequired,
+      // Provided by wrapping the component with FluentReact.withLocalization.
+      getString: PropTypes.func.isRequired,
+      icon: PropTypes.string.isRequired,
+      isCollapsed: PropTypes.bool.isRequired,
+      name: PropTypes.string.isRequired,
+      targets: PropTypes.arrayOf(Types.debugTarget).isRequired,
+    };
+  }
+
+  constructor(props) {
+    super(props);
+    this.collapsableRef = createRef();
+  }
+
+  componentDidUpdate(prevProps, prevState, snapshot) {
+    if (snapshot === null) {
+      return;
+    }
+
+    const el = this.collapsableRef.current;
+
+    // Cancel existing animation which is collapsing/expanding.
+    for (const animation of el.getAnimations()) {
+      animation.cancel();
+    }
+
+    el.animate(
+      { maxHeight: [`${snapshot}px`, `${el.clientHeight}px`] },
+      { duration: 150, easing: "cubic-bezier(.07, .95, 0, 1)" }
+    );
+  }
+
+  getSnapshotBeforeUpdate(prevProps) {
+    if (this.props.isCollapsed !== prevProps.isCollapsed) {
+      return this.collapsableRef.current.clientHeight;
+    }
+
+    return null;
+  }
+
+  toggleCollapsibility() {
+    const { collapsibilityKey, dispatch, isCollapsed } = this.props;
+    dispatch(
+      Actions.updateDebugTargetCollapsibility(collapsibilityKey, !isCollapsed)
+    );
+  }
+
+  render() {
+    const {
+      actionComponent,
+      additionalActionsComponent,
+      children,
+      detailComponent,
+      dispatch,
+      getString,
+      icon,
+      isCollapsed,
+      name,
+      targets,
+    } = this.props;
+
+    const title = getString("about-debugging-collapse-expand-debug-targets");
+
+    return dom.section(
+      {
+        className: "qa-debug-target-pane",
+      },
+      dom.a(
+        {
+          className:
+            "undecorated-link debug-target-pane__title " +
+            "qa-debug-target-pane-title",
+          title,
+          onClick: e => this.toggleCollapsibility(),
+        },
+        dom.h2(
+          { className: "main-subheading debug-target-pane__heading" },
+          dom.img({
+            className: "main-subheading__icon",
+            src: icon,
+          }),
+          `${name} (${targets.length})`,
+          dom.img({
+            className:
+              "main-subheading__icon debug-target-pane__icon" +
+              (isCollapsed ? " debug-target-pane__icon--collapsed" : ""),
+            src: "chrome://devtools/skin/images/arrow-e.svg",
+          })
+        )
+      ),
+      dom.div(
+        {
+          className:
+            "debug-target-pane__collapsable qa-debug-target-pane__collapsable" +
+            (isCollapsed ? " debug-target-pane__collapsable--collapsed" : ""),
+          ref: this.collapsableRef,
+        },
+        children,
+        DebugTargetList({
+          actionComponent,
+          additionalActionsComponent,
+          detailComponent,
+          dispatch,
+          isCollapsed,
+          targets,
+        })
+      )
+    );
+  }
+}
+
+module.exports = FluentReact.withLocalization(DebugTargetPane);
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/ExtensionDetail.css b/devtools/client/aboutdebugging/src/components/debugtarget/ExtensionDetail.css
new file mode 100644
index 0000000000..6a4befa76a
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/ExtensionDetail.css
@@ -0,0 +1,27 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.extension-backgroundscript {
+  display: flex;
+  column-gap: calc(var(--base-unit) * 2);
+}
+
+.extension-backgroundscript__status {
+  display: flex;
+  align-items: center;
+  float: inline-end;
+}
+
+.extension-backgroundscript__status::before {
+  background-color: var(--grey-50);
+  border-radius: 100%;
+  content: "";
+  height: calc(var(--base-unit) * 2);
+  margin-inline-end: var(--base-unit);
+  width: calc(var(--base-unit) * 2);
+}
+
+.extension-backgroundscript__status--running::before {
+  background-color: var(--success-background);
+}
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/ExtensionDetail.js b/devtools/client/aboutdebugging/src/components/debugtarget/ExtensionDetail.js
new file mode 100644
index 0000000000..ef14483723
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/ExtensionDetail.js
@@ -0,0 +1,243 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+const {
+  connect,
+} = require("resource://devtools/client/shared/vendor/react-redux.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  getCurrentRuntimeDetails,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js");
+
+const DetailsLog = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/DetailsLog.js")
+);
+const FieldPair = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.js")
+);
+const Message = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/Message.js")
+);
+
+const {
+  EXTENSION_BGSCRIPT_STATUSES,
+  MESSAGE_LEVEL,
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component displays detail information for extension.
+ */
+class ExtensionDetail extends PureComponent {
+  static get propTypes() {
+    return {
+      children: PropTypes.node,
+      // Provided by wrapping the component with FluentReact.withLocalization.
+      getString: PropTypes.func.isRequired,
+      // Provided by redux state
+      runtimeDetails: Types.runtimeDetails.isRequired,
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  renderWarnings() {
+    const { warnings } = this.props.target.details;
+
+    if (!warnings.length) {
+      return null;
+    }
+
+    return dom.section(
+      {
+        className: "debug-target-item__messages",
+      },
+      warnings.map((warning, index) => {
+        return Message(
+          {
+            level: MESSAGE_LEVEL.WARNING,
+            isCloseable: true,
+            key: `warning-${index}`,
+          },
+          DetailsLog(
+            {
+              type: MESSAGE_LEVEL.WARNING,
+            },
+            dom.p(
+              {
+                className: "technical-text",
+              },
+              warning
+            )
+          )
+        );
+      })
+    );
+  }
+
+  renderUUID() {
+    const { uuid } = this.props.target.details;
+    if (!uuid) {
+      return null;
+    }
+
+    return Localized(
+      {
+        id: "about-debugging-extension-uuid",
+        attrs: { label: true },
+      },
+      FieldPair({
+        label: "Internal UUID",
+        value: uuid,
+      })
+    );
+  }
+
+  renderExtensionId() {
+    const { id } = this.props.target;
+
+    return Localized(
+      {
+        id: "about-debugging-extension-id",
+        attrs: { label: true },
+      },
+      FieldPair({
+        label: "Extension ID",
+        value: id,
+      })
+    );
+  }
+
+  renderLocation() {
+    const { location } = this.props.target.details;
+    if (!location) {
+      return null;
+    }
+
+    return Localized(
+      {
+        id: "about-debugging-extension-location",
+        attrs: { label: true },
+      },
+      FieldPair({
+        label: "Location",
+        value: location,
+      })
+    );
+  }
+
+  renderManifest() {
+    // Manifest links are only relevant when debugging the current Firefox
+    // instance.
+    if (this.props.runtimeDetails.info.type !== RUNTIMES.THIS_FIREFOX) {
+      return null;
+    }
+
+    const { manifestURL } = this.props.target.details;
+    const link = dom.a(
+      {
+        className: "qa-manifest-url",
+        href: manifestURL,
+        target: "_blank",
+      },
+      manifestURL
+    );
+
+    return Localized(
+      {
+        id: "about-debugging-extension-manifest-url",
+        attrs: { label: true },
+      },
+      FieldPair({
+        label: "Manifest URL",
+        value: link,
+      })
+    );
+  }
+
+  renderBackgroundScriptStatus() {
+    // The status of the background script is only relevant if it is
+    // not persistent.
+    const { persistentBackgroundScript } = this.props.target.details;
+    if (!(persistentBackgroundScript === false)) {
+      return null;
+    }
+
+    const { backgroundScriptStatus } = this.props.target.details;
+
+    let status;
+    let statusLocalizationId;
+    let statusClassName;
+
+    if (backgroundScriptStatus === EXTENSION_BGSCRIPT_STATUSES.RUNNING) {
+      status = `extension-backgroundscript__status--running`;
+      statusLocalizationId = `about-debugging-extension-backgroundscript-status-running`;
+      statusClassName = `extension-backgroundscript__status--running`;
+    } else {
+      status = `extension-backgroundscript__status--stopped`;
+      statusLocalizationId = `about-debugging-extension-backgroundscript-status-stopped`;
+      statusClassName = `extension-backgroundscript__status--stopped`;
+    }
+
+    return Localized(
+      {
+        id: "about-debugging-extension-backgroundscript",
+        attrs: { label: true },
+      },
+      FieldPair({
+        label: "Background Script",
+        value: Localized(
+          {
+            id: statusLocalizationId,
+          },
+          dom.span(
+            {
+              className: `extension-backgroundscript__status qa-extension-backgroundscript-status ${statusClassName}`,
+            },
+            status
+          )
+        ),
+      })
+    );
+  }
+
+  render() {
+    return dom.section(
+      {
+        className: "debug-target-item__detail",
+      },
+      this.renderWarnings(),
+      dom.dl(
+        {},
+        this.renderLocation(),
+        this.renderExtensionId(),
+        this.renderUUID(),
+        this.renderManifest(),
+        this.renderBackgroundScriptStatus(),
+        this.props.children
+      )
+    );
+  }
+}
+
+const mapStateToProps = state => {
+  return {
+    runtimeDetails: getCurrentRuntimeDetails(state.runtimes),
+  };
+};
+
+module.exports = FluentReact.withLocalization(
+  connect(mapStateToProps)(ExtensionDetail)
+);
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.css b/devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.css
new file mode 100644
index 0000000000..a0b290d2a3
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.css
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.fieldpair {
+  display: grid;
+  grid-template-columns: auto auto;
+  border-top: 1px solid var(--card-separator-color);
+  padding-block: calc(var(--base-unit) * 2);
+  padding-inline: calc(var(--base-unit) * 4) calc(var(--base-unit) * 2);
+}
+
+.fieldpair:last-child {
+  padding-block-end: 0;
+}
+
+.fieldpair__title {
+  margin-inline-end: var(--base-unit);
+  font-size: var(--caption-20-font-size);
+  font-weight: var(--caption-20-font-weight);
+}
+
+.fieldpair__description {
+  color: var(--fieldpair-text-color);
+  flex: 1;
+  font-size: var(--caption-20-font-size);
+  font-weight: var(--caption-20-font-weight);
+  text-align: end;
+}
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.js b/devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.js
new file mode 100644
index 0000000000..5e7ae53c65
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.js
@@ -0,0 +1,49 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+/* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+/* Renders a pair of `<dt>` (label) + `<dd>` (value) field. */
+class FieldPair extends PureComponent {
+  static get propTypes() {
+    return {
+      className: PropTypes.string,
+      label: PropTypes.node.isRequired,
+      value: PropTypes.node,
+    };
+  }
+
+  render() {
+    const { label, value } = this.props;
+    return dom.div(
+      {
+        className: "fieldpair",
+      },
+      dom.dt(
+        {
+          className:
+            "fieldpair__title " +
+            (this.props.className ? this.props.className : ""),
+        },
+        label
+      ),
+      value
+        ? dom.dd(
+            {
+              className: "fieldpair__description ellipsis-text",
+            },
+            value
+          )
+        : null
+    );
+  }
+}
+
+module.exports = FieldPair;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/InspectAction.js b/devtools/client/aboutdebugging/src/components/debugtarget/InspectAction.js
new file mode 100644
index 0000000000..f7aff438a4
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/InspectAction.js
@@ -0,0 +1,58 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component provides inspect button.
+ */
+class InspectAction extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      disabled: PropTypes.bool,
+      target: Types.debugTarget.isRequired,
+      title: PropTypes.string,
+    };
+  }
+
+  inspect() {
+    const { dispatch, target } = this.props;
+    dispatch(Actions.inspectDebugTarget(target.type, target.id));
+  }
+
+  render() {
+    const { disabled, title } = this.props;
+
+    return Localized(
+      {
+        id: "about-debugging-debug-target-inspect-button",
+      },
+      dom.button(
+        {
+          onClick: e => this.inspect(),
+          className: "default-button  qa-debug-target-inspect-button",
+          disabled,
+          title,
+        },
+        "Inspect"
+      )
+    );
+  }
+}
+
+module.exports = InspectAction;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/ProcessDetail.js b/devtools/client/aboutdebugging/src/components/debugtarget/ProcessDetail.js
new file mode 100644
index 0000000000..a9973e90e3
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/ProcessDetail.js
@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component displays detail information for a process.
+ */
+class ProcessDetail extends PureComponent {
+  static get propTypes() {
+    return {
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  render() {
+    const { description } = this.props.target.details;
+    return dom.p(
+      { className: "debug-target-item__subname ellipsis-text" },
+      description
+    );
+  }
+}
+
+module.exports = ProcessDetail;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAction.css b/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAction.css
new file mode 100644
index 0000000000..c3ac2dc872
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAction.css
@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.service-worker-action {
+  display: flex;
+  column-gap: calc(var(--base-unit) * 2);
+}
+
+.service-worker-action__status {
+  display: flex;
+  align-items: center;
+}
+
+.service-worker-action__status::before {
+  background-color: var(--grey-50);
+  border-radius: 100%;
+  content: "";
+  height: calc(var(--base-unit) * 2);
+  margin-inline-end: var(--base-unit);
+  width: calc(var(--base-unit) * 2);
+}
+
+.service-worker-action__status--running::before {
+  background-color: var(--success-background);
+}
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAction.js b/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAction.js
new file mode 100644
index 0000000000..38aede94f4
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAction.js
@@ -0,0 +1,124 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+const {
+  connect,
+} = require("resource://devtools/client/shared/vendor/react-redux.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  getCurrentRuntimeDetails,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js");
+
+const InspectAction = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/InspectAction.js")
+);
+
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+const {
+  SERVICE_WORKER_STATUSES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This component displays buttons for service worker.
+ */
+class ServiceWorkerAction extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      // Provided by redux state
+      runtimeDetails: Types.runtimeDetails.isRequired,
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  _renderInspectAction() {
+    const { status } = this.props.target.details;
+    const shallRenderInspectAction =
+      status === SERVICE_WORKER_STATUSES.RUNNING ||
+      status === SERVICE_WORKER_STATUSES.REGISTERING;
+
+    if (!shallRenderInspectAction) {
+      return null;
+    }
+
+    const { canDebugServiceWorkers } = this.props.runtimeDetails;
+    return Localized(
+      {
+        id: "about-debugging-worker-inspect-action-disabled",
+        attrs: {
+          // Show an explanatory title only if the action is disabled.
+          title: !canDebugServiceWorkers,
+        },
+      },
+      InspectAction({
+        disabled: !canDebugServiceWorkers,
+        dispatch: this.props.dispatch,
+        target: this.props.target,
+      })
+    );
+  }
+
+  _getStatusLocalizationId(status) {
+    switch (status) {
+      case SERVICE_WORKER_STATUSES.REGISTERING.toLowerCase():
+        return "about-debugging-worker-status-registering";
+      case SERVICE_WORKER_STATUSES.RUNNING.toLowerCase():
+        return "about-debugging-worker-status-running";
+      case SERVICE_WORKER_STATUSES.STOPPED.toLowerCase():
+        return "about-debugging-worker-status-stopped";
+      default:
+        // Assume status is stopped for unknown status value.
+        return "about-debugging-worker-status-stopped";
+    }
+  }
+
+  _renderStatus() {
+    const status = this.props.target.details.status.toLowerCase();
+    const statusClassName =
+      status === SERVICE_WORKER_STATUSES.RUNNING.toLowerCase()
+        ? "service-worker-action__status--running"
+        : "";
+
+    return Localized(
+      {
+        id: this._getStatusLocalizationId(status),
+      },
+      dom.span(
+        {
+          className: `service-worker-action__status qa-worker-status ${statusClassName}`,
+        },
+        status
+      )
+    );
+  }
+
+  render() {
+    return dom.div(
+      {
+        className: "service-worker-action",
+      },
+      this._renderStatus(),
+      this._renderInspectAction()
+    );
+  }
+}
+
+const mapStateToProps = state => {
+  return {
+    runtimeDetails: getCurrentRuntimeDetails(state.runtimes),
+  };
+};
+
+module.exports = connect(mapStateToProps)(ServiceWorkerAction);
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAdditionalActions.js b/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAdditionalActions.js
new file mode 100644
index 0000000000..38262ad511
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/ServiceWorkerAdditionalActions.js
@@ -0,0 +1,176 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+const {
+  connect,
+} = require("resource://devtools/client/shared/vendor/react-redux.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  getCurrentRuntimeDetails,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js");
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+const {
+  SERVICE_WORKER_STATUSES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * The main purpose of this component is to expose a meaningful prop
+ * disabledTitle that can be used with fluent localization.
+ */
+class _ActionButton extends PureComponent {
+  static get propTypes() {
+    return {
+      children: PropTypes.node,
+      className: PropTypes.string.isRequired,
+      disabled: PropTypes.bool,
+      disabledTitle: PropTypes.string,
+      onClick: PropTypes.func.isRequired,
+    };
+  }
+
+  render() {
+    const { className, disabled, disabledTitle, onClick } = this.props;
+    return dom.button(
+      {
+        className,
+        disabled,
+        onClick: e => onClick(),
+        title: disabled && disabledTitle ? disabledTitle : undefined,
+      },
+      this.props.children
+    );
+  }
+}
+const ActionButtonFactory = createFactory(_ActionButton);
+
+/**
+ * This component displays buttons for service worker.
+ */
+class ServiceWorkerAdditionalActions extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      // Provided by wrapping the component with FluentReact.withLocalization.
+      getString: PropTypes.func.isRequired,
+      // Provided by redux state
+      runtimeDetails: Types.runtimeDetails.isRequired,
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  push() {
+    const { dispatch, target } = this.props;
+    dispatch(
+      Actions.pushServiceWorker(target.id, target.details.registrationFront)
+    );
+  }
+
+  start() {
+    const { dispatch, target } = this.props;
+    dispatch(Actions.startServiceWorker(target.details.registrationFront));
+  }
+
+  unregister() {
+    const { dispatch, target } = this.props;
+    dispatch(Actions.unregisterServiceWorker(target.details.registrationFront));
+  }
+
+  _renderButton({ className, disabled, key, labelId, onClick }) {
+    return Localized(
+      {
+        id: labelId,
+        attrs: {
+          disabledTitle: !!disabled,
+        },
+        key,
+      },
+      ActionButtonFactory(
+        {
+          className,
+          disabled,
+          onClick: e => onClick(),
+        },
+        labelId
+      )
+    );
+  }
+
+  _renderPushButton() {
+    return this._renderButton({
+      className: "default-button default-button--micro qa-push-button",
+      disabled: !this.props.runtimeDetails.canDebugServiceWorkers,
+      key: "service-worker-push-button",
+      labelId: "about-debugging-worker-action-push2",
+      onClick: this.push.bind(this),
+    });
+  }
+
+  _renderStartButton() {
+    return this._renderButton({
+      className: "default-button default-button--micro qa-start-button",
+      disabled: !this.props.runtimeDetails.canDebugServiceWorkers,
+      key: "service-worker-start-button",
+      labelId: "about-debugging-worker-action-start2",
+      onClick: this.start.bind(this),
+    });
+  }
+
+  _renderUnregisterButton() {
+    return this._renderButton({
+      className: "default-button default-button--micro qa-unregister-button",
+      key: "service-worker-unregister-button",
+      labelId: "about-debugging-worker-action-unregister",
+      disabled: false,
+      onClick: this.unregister.bind(this),
+    });
+  }
+
+  _renderActionButtons() {
+    const { status } = this.props.target.details;
+
+    switch (status) {
+      case SERVICE_WORKER_STATUSES.RUNNING:
+        return [this._renderUnregisterButton(), this._renderPushButton()];
+      case SERVICE_WORKER_STATUSES.REGISTERING:
+        return null;
+      case SERVICE_WORKER_STATUSES.STOPPED:
+        return [this._renderUnregisterButton(), this._renderStartButton()];
+      default:
+        console.error("Unexpected service worker status: " + status);
+        return null;
+    }
+  }
+
+  render() {
+    return dom.div(
+      {
+        className: "toolbar toolbar--right-align",
+      },
+      this._renderActionButtons()
+    );
+  }
+}
+
+const mapStateToProps = state => {
+  return {
+    runtimeDetails: getCurrentRuntimeDetails(state.runtimes),
+  };
+};
+
+module.exports = FluentReact.withLocalization(
+  connect(mapStateToProps)(ServiceWorkerAdditionalActions)
+);
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/TabAction.js b/devtools/client/aboutdebugging/src/components/debugtarget/TabAction.js
new file mode 100644
index 0000000000..132f1e5f44
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/TabAction.js
@@ -0,0 +1,52 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const InspectAction = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/InspectAction.js")
+);
+
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component displays the inspect button for tabs.
+ */
+class TabAction extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  render() {
+    const isZombieTab = this.props.target.details.isZombieTab;
+    return Localized(
+      {
+        id: "about-debugging-zombie-tab-inspect-action-disabled",
+        attrs: {
+          // Show an explanatory title only if the action is disabled.
+          title: isZombieTab,
+        },
+      },
+      InspectAction({
+        disabled: isZombieTab,
+        dispatch: this.props.dispatch,
+        target: this.props.target,
+      })
+    );
+  }
+}
+
+module.exports = FluentReact.withLocalization(TabAction);
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/TabDetail.js b/devtools/client/aboutdebugging/src/components/debugtarget/TabDetail.js
new file mode 100644
index 0000000000..dcbd3f0a4d
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/TabDetail.js
@@ -0,0 +1,34 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component displays detail information for tab.
+ */
+class TabDetail extends PureComponent {
+  static get propTypes() {
+    return {
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  render() {
+    return dom.div(
+      {
+        className: "debug-target-item__subname ellipsis-text",
+        dir: "ltr",
+      },
+      this.props.target.details.url
+    );
+  }
+}
+
+module.exports = TabDetail;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionAdditionalActions.js b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionAdditionalActions.js
new file mode 100644
index 0000000000..44b7d3e167
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionAdditionalActions.js
@@ -0,0 +1,182 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+const DetailsLog = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/DetailsLog.js")
+);
+const Message = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/Message.js")
+);
+const {
+  MESSAGE_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This component provides components that reload/remove temporary extension.
+ */
+class TemporaryExtensionAdditionalActions extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  reload() {
+    const { dispatch, target } = this.props;
+    dispatch(Actions.reloadTemporaryExtension(target.id));
+  }
+
+  terminateBackgroundScript() {
+    const { dispatch, target } = this.props;
+    dispatch(Actions.terminateExtensionBackgroundScript(target.id));
+  }
+
+  remove() {
+    const { dispatch, target } = this.props;
+    dispatch(Actions.removeTemporaryExtension(target.id));
+  }
+
+  renderReloadError() {
+    const { reloadError } = this.props.target.details;
+
+    if (!reloadError) {
+      return null;
+    }
+
+    return Message(
+      {
+        className: "qa-temporary-extension-reload-error",
+        level: MESSAGE_LEVEL.ERROR,
+        key: "reload-error",
+      },
+      DetailsLog(
+        {
+          type: MESSAGE_LEVEL.ERROR,
+        },
+        dom.p(
+          {
+            className: "technical-text",
+          },
+          reloadError
+        )
+      )
+    );
+  }
+
+  renderTerminateBackgroundScriptError() {
+    const { lastTerminateBackgroundScriptError } = this.props.target.details;
+
+    if (!lastTerminateBackgroundScriptError) {
+      return null;
+    }
+
+    return Message(
+      {
+        className: "qa-temporary-extension-terminate-backgroundscript-error",
+        level: MESSAGE_LEVEL.ERROR,
+        key: "terminate-backgroundscript-error",
+      },
+      DetailsLog(
+        {
+          type: MESSAGE_LEVEL.ERROR,
+        },
+        dom.p(
+          {
+            className: "technical-text",
+          },
+          lastTerminateBackgroundScriptError
+        )
+      )
+    );
+  }
+
+  renderTerminateBackgroundScriptButton() {
+    const { persistentBackgroundScript } = this.props.target.details;
+
+    // For extensions with a non persistent background script
+    // also include a "terminate background script" action.
+    if (persistentBackgroundScript !== false) {
+      return null;
+    }
+
+    return Localized(
+      {
+        id: "about-debugging-tmp-extension-terminate-bgscript-button",
+      },
+      dom.button(
+        {
+          className:
+            "default-button default-button--micro " +
+            "qa-temporary-extension-terminate-bgscript-button",
+          onClick: e => this.terminateBackgroundScript(),
+        },
+        "Terminate Background Script"
+      )
+    );
+  }
+
+  renderRemoveButton() {
+    return Localized(
+      {
+        id: "about-debugging-tmp-extension-remove-button",
+      },
+      dom.button(
+        {
+          className:
+            "default-button default-button--micro " +
+            "qa-temporary-extension-remove-button",
+          onClick: e => this.remove(),
+        },
+        "Remove"
+      )
+    );
+  }
+
+  render() {
+    return [
+      dom.div(
+        {
+          className: "toolbar toolbar--right-align",
+          key: "actions",
+        },
+        this.renderTerminateBackgroundScriptButton(),
+        Localized(
+          {
+            id: "about-debugging-tmp-extension-reload-button",
+          },
+          dom.button(
+            {
+              className:
+                "default-button default-button--micro " +
+                "qa-temporary-extension-reload-button",
+              onClick: e => this.reload(),
+            },
+            "Reload"
+          )
+        ),
+        this.renderRemoveButton()
+      ),
+      this.renderReloadError(),
+      this.renderTerminateBackgroundScriptError(),
+    ];
+  }
+}
+
+module.exports = TemporaryExtensionAdditionalActions;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionDetail.js b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionDetail.js
new file mode 100644
index 0000000000..6c589472d6
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionDetail.js
@@ -0,0 +1,67 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const ExtensionDetail = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/ExtensionDetail.js")
+);
+const FieldPair = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.js")
+);
+
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+const TEMP_ID_DOC_URL =
+  "https://developer.mozilla.org/Add-ons/WebExtensions/WebExtensions_and_the_Add-on_ID";
+
+/**
+ * This component displays detail information for a temporary extension.
+ */
+class TemporaryExtensionDetail extends PureComponent {
+  static get propTypes() {
+    return {
+      // Provided by wrapping the component with FluentReact.withLocalization.
+      getString: PropTypes.func.isRequired,
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  renderTemporaryIdMessage() {
+    return Localized(
+      {
+        id: "about-debugging-tmp-extension-temporary-id",
+        a: dom.a({
+          className: "qa-temporary-id-link",
+          href: TEMP_ID_DOC_URL,
+          target: "_blank",
+        }),
+      },
+      dom.div({
+        className: "qa-temporary-id-message",
+      })
+    );
+  }
+
+  render() {
+    return ExtensionDetail(
+      {
+        target: this.props.target,
+      },
+      FieldPair({ label: this.renderTemporaryIdMessage() })
+    );
+  }
+}
+
+module.exports = FluentReact.withLocalization(TemporaryExtensionDetail);
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstallSection.css b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstallSection.css
new file mode 100644
index 0000000000..9166a3b615
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstallSection.css
@@ -0,0 +1,8 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.temporary-extension-install-section__toolbar {
+  display: flex;
+  justify-content: end;
+}
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstallSection.js b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstallSection.js
new file mode 100644
index 0000000000..f85618f73d
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstallSection.js
@@ -0,0 +1,101 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const DetailsLog = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/DetailsLog.js")
+);
+const Message = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/Message.js")
+);
+const TemporaryExtensionInstaller = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstaller.js")
+);
+
+const {
+  MESSAGE_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This component provides an installer and error message area for temporary extension.
+ */
+class TemporaryExtensionInstallSection extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      temporaryInstallError: PropTypes.object,
+    };
+  }
+
+  renderError() {
+    const { temporaryInstallError } = this.props;
+
+    if (!temporaryInstallError) {
+      return null;
+    }
+
+    const errorMessages = [
+      temporaryInstallError.message,
+      ...(temporaryInstallError.additionalErrors || []),
+    ];
+
+    const errors = errorMessages.map((message, index) => {
+      return dom.p(
+        {
+          className: "technical-text",
+          key: "tmp-extension-install-error-" + index,
+        },
+        message
+      );
+    });
+
+    return Message(
+      {
+        level: MESSAGE_LEVEL.ERROR,
+        className: "qa-tmp-extension-install-error",
+        isCloseable: true,
+      },
+      Localized(
+        {
+          id: "about-debugging-tmp-extension-install-error",
+        },
+        dom.p({}, "about-debugging-tmp-extension-install-error")
+      ),
+      DetailsLog(
+        {
+          type: MESSAGE_LEVEL.ERROR,
+        },
+        errors
+      )
+    );
+  }
+
+  render() {
+    const { dispatch } = this.props;
+
+    return dom.section(
+      {},
+      dom.div(
+        {
+          className: "temporary-extension-install-section__toolbar",
+        },
+        TemporaryExtensionInstaller({ dispatch })
+      ),
+      this.renderError()
+    );
+  }
+}
+
+module.exports = TemporaryExtensionInstallSection;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstaller.js b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstaller.js
new file mode 100644
index 0000000000..e515c647ec
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/TemporaryExtensionInstaller.js
@@ -0,0 +1,52 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+
+/**
+ * This component provides an installer for temporary extension.
+ */
+class TemporaryExtensionInstaller extends PureComponent {
+  static get propTypes() {
+    return {
+      className: PropTypes.string,
+      dispatch: PropTypes.func.isRequired,
+    };
+  }
+
+  install() {
+    this.props.dispatch(Actions.installTemporaryExtension());
+  }
+
+  render() {
+    const { className } = this.props;
+
+    return Localized(
+      {
+        id: "about-debugging-tmp-extension-install-button",
+      },
+      dom.button(
+        {
+          className: `${className} default-button qa-temporary-extension-install-button`,
+          onClick: e => this.install(),
+        },
+        "Load Temporary Add-on…"
+      )
+    );
+  }
+}
+
+module.exports = TemporaryExtensionInstaller;
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/WorkerDetail.js b/devtools/client/aboutdebugging/src/components/debugtarget/WorkerDetail.js
new file mode 100644
index 0000000000..b69252c430
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/WorkerDetail.js
@@ -0,0 +1,120 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  SERVICE_WORKER_FETCH_STATES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const FieldPair = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/debugtarget/FieldPair.js")
+);
+
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+
+/**
+ * This component displays detail information for worker.
+ */
+class WorkerDetail extends PureComponent {
+  static get propTypes() {
+    return {
+      // Provided by wrapping the component with FluentReact.withLocalization.
+      getString: PropTypes.func.isRequired,
+      target: Types.debugTarget.isRequired,
+    };
+  }
+
+  renderFetch() {
+    const { fetch } = this.props.target.details;
+    const isListening = fetch === SERVICE_WORKER_FETCH_STATES.LISTENING;
+    const localizationId = isListening
+      ? "about-debugging-worker-fetch-listening"
+      : "about-debugging-worker-fetch-not-listening";
+
+    return Localized(
+      {
+        id: localizationId,
+        attrs: {
+          label: true,
+          value: true,
+        },
+      },
+      FieldPair({
+        className: isListening
+          ? "qa-worker-fetch-listening"
+          : "qa-worker-fetch-not-listening",
+        label: "Fetch",
+        slug: "fetch",
+        value: "about-debugging-worker-fetch-value",
+      })
+    );
+  }
+
+  renderPushService() {
+    const { pushServiceEndpoint } = this.props.target.details;
+
+    return Localized(
+      {
+        id: "about-debugging-worker-push-service",
+        attrs: { label: true },
+      },
+      FieldPair({
+        slug: "push-service",
+        label: "Push Service",
+        value: dom.span(
+          {
+            className: "qa-worker-push-service-value",
+          },
+          pushServiceEndpoint
+        ),
+      })
+    );
+  }
+
+  renderScope() {
+    const { scope } = this.props.target.details;
+
+    return Localized(
+      {
+        id: "about-debugging-worker-scope",
+        attrs: { label: true },
+      },
+      FieldPair({
+        slug: "scope",
+        label: "Scope",
+        value: scope,
+      })
+    );
+  }
+
+  render() {
+    const { fetch, pushServiceEndpoint, scope } = this.props.target.details;
+
+    const isEmptyList = !pushServiceEndpoint && !fetch && !scope && !status;
+
+    return dom.dl(
+      {
+        className:
+          "debug-target-item__detail" +
+          (isEmptyList ? " debug-target-item__detail--empty" : ""),
+      },
+      pushServiceEndpoint ? this.renderPushService() : null,
+      fetch ? this.renderFetch() : null,
+      scope ? this.renderScope() : null
+    );
+  }
+}
+
+module.exports = FluentReact.withLocalization(WorkerDetail);
diff --git a/devtools/client/aboutdebugging/src/components/debugtarget/moz.build b/devtools/client/aboutdebugging/src/components/debugtarget/moz.build
new file mode 100644
index 0000000000..981e6887a2
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/debugtarget/moz.build
@@ -0,0 +1,22 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "DebugTargetItem.js",
+    "DebugTargetList.js",
+    "DebugTargetPane.js",
+    "ExtensionDetail.js",
+    "FieldPair.js",
+    "InspectAction.js",
+    "ProcessDetail.js",
+    "ServiceWorkerAction.js",
+    "ServiceWorkerAdditionalActions.js",
+    "TabAction.js",
+    "TabDetail.js",
+    "TemporaryExtensionAdditionalActions.js",
+    "TemporaryExtensionDetail.js",
+    "TemporaryExtensionInstaller.js",
+    "TemporaryExtensionInstallSection.js",
+    "WorkerDetail.js",
+)
diff --git a/devtools/client/aboutdebugging/src/components/moz.build b/devtools/client/aboutdebugging/src/components/moz.build
new file mode 100644
index 0000000000..c48d384b3d
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/moz.build
@@ -0,0 +1,21 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += [
+    "connect",
+    "debugtarget",
+    "shared",
+    "sidebar",
+]
+
+DevToolsModules(
+    "App.js",
+    "CompatibilityWarning.js",
+    "ConnectionPromptSetting.js",
+    "ProfilerDialog.js",
+    "RuntimeActions.js",
+    "RuntimeInfo.js",
+    "RuntimePage.js",
+    "ServiceWorkersWarning.js",
+)
diff --git a/devtools/client/aboutdebugging/src/components/shared/DetailsLog.js b/devtools/client/aboutdebugging/src/components/shared/DetailsLog.js
new file mode 100644
index 0000000000..f10c8a487d
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/shared/DetailsLog.js
@@ -0,0 +1,64 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  MESSAGE_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This component is designed to wrap a warning / error log message
+ * in the details tag to hide long texts and make the message expendable
+ * out of the box.
+ */
+class DetailsLog extends PureComponent {
+  static get propTypes() {
+    return {
+      children: PropTypes.node.isRequired,
+      type: PropTypes.string,
+    };
+  }
+  getLocalizationString() {
+    const { type } = this.props;
+
+    switch (type) {
+      case MESSAGE_LEVEL.WARNING:
+        return "about-debugging-message-details-label-warning";
+      case MESSAGE_LEVEL.ERROR:
+        return "about-debugging-message-details-label-error";
+      default:
+        return "about-debugging-message-details-label";
+    }
+  }
+
+  render() {
+    const { children } = this.props;
+
+    return dom.details(
+      {
+        className: "details--log",
+      },
+      Localized(
+        {
+          id: this.getLocalizationString(),
+        },
+        dom.summary({}, this.getLocalizationString())
+      ),
+      children
+    );
+  }
+}
+
+module.exports = DetailsLog;
diff --git a/devtools/client/aboutdebugging/src/components/shared/IconLabel.css b/devtools/client/aboutdebugging/src/components/shared/IconLabel.css
new file mode 100644
index 0000000000..ddb7c3929a
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/shared/IconLabel.css
@@ -0,0 +1,27 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.icon-label {
+  display: flex;
+  column-gap: var(--base-unit);
+  align-items: center;
+  margin: calc(var(--base-unit) * 2) 0;
+  -moz-context-properties: fill;
+
+  font-size: var(--icon-label-font-size);
+}
+
+.icon-label--ok {
+  --icon-color: var(--icon-ok-color);
+}
+.icon-label--info {
+  --icon-color: var(--icon-info-color);
+}
+
+.icon-label__icon {
+  padding: var(--base-unit);
+  fill: var(--icon-color);
+  width: calc(var(--base-unit) * 4);
+  height: calc(var(--base-unit) * 4);
+}
diff --git a/devtools/client/aboutdebugging/src/components/shared/IconLabel.js b/devtools/client/aboutdebugging/src/components/shared/IconLabel.js
new file mode 100644
index 0000000000..3141e75640
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/shared/IconLabel.js
@@ -0,0 +1,48 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const {
+  ICON_LABEL_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const ICONS = {
+  [ICON_LABEL_LEVEL.INFO]: "chrome://devtools/skin/images/info.svg",
+  [ICON_LABEL_LEVEL.OK]: "chrome://devtools/skin/images/check.svg",
+};
+
+/* This component displays an icon accompanied by some content. It's similar
+   to a message, but it's not interactive */
+class IconLabel extends PureComponent {
+  static get propTypes() {
+    return {
+      children: PropTypes.node.isRequired,
+      className: PropTypes.string,
+      level: PropTypes.oneOf(Object.values(ICON_LABEL_LEVEL)).isRequired,
+    };
+  }
+
+  render() {
+    const { children, className, level } = this.props;
+    return dom.span(
+      {
+        className: `icon-label icon-label--${level} ${className || ""}`,
+      },
+      dom.img({
+        className: "icon-label__icon",
+        src: ICONS[level],
+      }),
+      children
+    );
+  }
+}
+
+module.exports = IconLabel;
diff --git a/devtools/client/aboutdebugging/src/components/shared/Message.css b/devtools/client/aboutdebugging/src/components/shared/Message.css
new file mode 100644
index 0000000000..e2c71c50b4
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/shared/Message.css
@@ -0,0 +1,79 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.message--level-error {
+  --message-background-color: var(--error-background);
+  --message-border-color: var(--error-border);
+  --message-color: var(--error-text);
+  --message-icon-color: var(--error-icon);
+}
+
+.message--level-info {
+  --message-background-color: var(--grey-20);
+  --message-border-color: transparent;
+  --message-color: var(--grey-90);
+  --message-icon-color: var(--grey-90);
+}
+
+.message--level-warning {
+  --message-background-color: var(--warning-background);
+  --message-border-color: var(--warning-border);
+  --message-color: var(--warning-text);
+  --message-icon-color: var(--warning-icon);
+}
+
+/*
+ * Layout of the message
+ *
+ *  +--------+-----------------+----------+
+ *  | Icon   | Message content | closing  |
+ *  |        | (several lines) | button   |
+ *  |        | (     ...     ) |(optional)|
+ *  +--------+-----------------+----------+
+ */
+.message {
+  background-color: var(--message-background-color);
+  border: 1px solid var(--message-border-color);
+  border-radius: var(--base-unit);
+  color: var(--message-color);
+  display: grid;
+  grid-column-gap: var(--base-unit);
+  grid-template-columns: calc(var(--base-unit) * 6) 1fr auto;
+  grid-template-areas:
+    "icon body button";
+  margin: calc(var(--base-unit) * 2) 0;
+  padding: var(--base-unit);
+  -moz-context-properties: fill;
+}
+
+.message__icon {
+  margin: var(--base-unit);
+  fill: var(--message-icon-color);
+  grid-area: icon;
+}
+
+.message__body {
+  align-self: center;
+  font-size: var(--message-font-size);
+  font-weight: 400;
+  grid-area: body;
+  line-height: 1.6;
+}
+
+.message__button {
+  grid-area: button;
+  fill: var(--message-icon-color);
+}
+
+.message__button:hover {
+  /* reverse colors with icon when hover state */
+  background-color: var(--message-icon-color);
+  fill: var(--message-background-color);
+}
+
+.message__button:active {
+  /* reverse colors with text when active state */
+  background-color: var(--message-color);
+  fill: var(--message-background-color);
+}
diff --git a/devtools/client/aboutdebugging/src/components/shared/Message.js b/devtools/client/aboutdebugging/src/components/shared/Message.js
new file mode 100644
index 0000000000..248db58dd3
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/shared/Message.js
@@ -0,0 +1,109 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  MESSAGE_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const ICONS = {
+  [MESSAGE_LEVEL.ERROR]:
+    "chrome://devtools/skin/images/aboutdebugging-error.svg",
+  [MESSAGE_LEVEL.INFO]:
+    "chrome://devtools/skin/images/aboutdebugging-information.svg",
+  [MESSAGE_LEVEL.WARNING]: "chrome://devtools/skin/images/alert.svg",
+};
+const CLOSE_ICON_SRC = "chrome://devtools/skin/images/close.svg";
+
+/**
+ * This component is designed to display a photon-style message bar. The component is
+ * responsible for displaying the message container with the appropriate icon. The content
+ * of the message should be passed as the children of this component.
+ */
+class Message extends PureComponent {
+  static get propTypes() {
+    return {
+      children: PropTypes.node.isRequired,
+      className: PropTypes.string,
+      isCloseable: PropTypes.bool,
+      level: PropTypes.oneOf(Object.values(MESSAGE_LEVEL)).isRequired,
+    };
+  }
+
+  constructor(props) {
+    super(props);
+    this.state = {
+      isClosed: false,
+    };
+  }
+
+  closeMessage() {
+    this.setState({ isClosed: true });
+  }
+
+  renderButton(level) {
+    return dom.button(
+      {
+        className:
+          `ghost-button message__button message__button--${level} ` +
+          `qa-message-button-close-button`,
+        onClick: () => this.closeMessage(),
+      },
+      Localized(
+        {
+          id: "about-debugging-message-close-icon",
+          attrs: {
+            alt: true,
+          },
+        },
+        dom.img({
+          className: "qa-message-button-close-icon",
+          src: CLOSE_ICON_SRC,
+        })
+      )
+    );
+  }
+
+  render() {
+    const { children, className, level, isCloseable } = this.props;
+    const { isClosed } = this.state;
+
+    if (isClosed) {
+      return null;
+    }
+
+    return dom.aside(
+      {
+        className:
+          `message message--level-${level}  qa-message` +
+          (className ? ` ${className}` : ""),
+      },
+      dom.img({
+        className: "message__icon",
+        src: ICONS[level],
+      }),
+      dom.div(
+        {
+          className: "message__body",
+        },
+        children
+      ),
+      // if the message is closeable, render a closing button
+      isCloseable ? this.renderButton(level) : null
+    );
+  }
+}
+
+module.exports = Message;
diff --git a/devtools/client/aboutdebugging/src/components/shared/moz.build b/devtools/client/aboutdebugging/src/components/shared/moz.build
new file mode 100644
index 0000000000..7e0e89f2a0
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/shared/moz.build
@@ -0,0 +1,9 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "DetailsLog.js",
+    "IconLabel.js",
+    "Message.js",
+)
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/RefreshDevicesButton.js b/devtools/client/aboutdebugging/src/components/sidebar/RefreshDevicesButton.js
new file mode 100644
index 0000000000..78ebb61661
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/RefreshDevicesButton.js
@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+
+class RefreshDevicesButton extends PureComponent {
+  static get propTypes() {
+    return {
+      dispatch: PropTypes.func.isRequired,
+      isScanning: PropTypes.bool.isRequired,
+    };
+  }
+
+  refreshDevices() {
+    this.props.dispatch(Actions.scanUSBRuntimes());
+  }
+
+  render() {
+    return Localized(
+      { id: "about-debugging-refresh-usb-devices-button" },
+      dom.button(
+        {
+          className: "default-button qa-refresh-devices-button",
+          disabled: this.props.isScanning,
+          onClick: () => this.refreshDevices(),
+        },
+        "Refresh devices"
+      )
+    );
+  }
+}
+
+module.exports = RefreshDevicesButton;
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/Sidebar.css b/devtools/client/aboutdebugging/src/components/sidebar/Sidebar.css
new file mode 100644
index 0000000000..afad630f6e
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/Sidebar.css
@@ -0,0 +1,43 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.sidebar {
+  display: grid;
+  grid-template-rows: auto auto;
+}
+
+.sidebar__label {
+  color: var(--secondary-text-color);
+  display: block;
+  padding: 12px 0;
+  text-align: center;
+  font-size: var(--message-font-size);
+}
+
+.sidebar__adb-status {
+  margin-block-end: calc(var(--base-unit) * 2);
+}
+
+.sidebar__refresh-usb {
+  text-align: center;
+}
+
+.sidebar__footer {
+  align-self: flex-end;
+}
+
+.sidebar__footer__support-help {
+  display: flex;
+  align-items: center;
+  justify-content: flex-start;
+  column-gap: calc(var(--base-unit) * 4);
+  height: 100%;
+}
+
+.sidebar__footer__icon {
+  width: calc(var(--base-unit) * 4);
+  height: calc(var(--base-unit) * 4);
+  -moz-context-properties: fill;
+  fill: currentColor;
+}
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/Sidebar.js b/devtools/client/aboutdebugging/src/components/sidebar/Sidebar.js
new file mode 100644
index 0000000000..3213b8141c
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/Sidebar.js
@@ -0,0 +1,259 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const {
+  ICON_LABEL_LEVEL,
+  PAGE_TYPES,
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const Types = require("resource://devtools/client/aboutdebugging/src/types/index.js");
+loader.lazyRequireGetter(
+  this,
+  "ADB_ADDON_STATES",
+  "resource://devtools/client/shared/remote-debugging/adb/adb-addon.js",
+  true
+);
+
+const IconLabel = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/IconLabel.js")
+);
+const SidebarItem = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.js")
+);
+const SidebarFixedItem = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/sidebar/SidebarFixedItem.js")
+);
+const SidebarRuntimeItem = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/sidebar/SidebarRuntimeItem.js")
+);
+const RefreshDevicesButton = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/sidebar/RefreshDevicesButton.js")
+);
+const FIREFOX_ICON =
+  "chrome://devtools/skin/images/aboutdebugging-firefox-logo.svg";
+const CONNECT_ICON = "chrome://devtools/skin/images/settings.svg";
+const GLOBE_ICON =
+  "chrome://devtools/skin/images/aboutdebugging-globe-icon.svg";
+const USB_ICON =
+  "chrome://devtools/skin/images/aboutdebugging-connect-icon.svg";
+
+class Sidebar extends PureComponent {
+  static get propTypes() {
+    return {
+      adbAddonStatus: Types.adbAddonStatus,
+      className: PropTypes.string,
+      dispatch: PropTypes.func.isRequired,
+      isAdbReady: PropTypes.bool.isRequired,
+      isScanningUsb: PropTypes.bool.isRequired,
+      networkRuntimes: PropTypes.arrayOf(Types.runtime).isRequired,
+      selectedPage: Types.page,
+      selectedRuntimeId: PropTypes.string,
+      usbRuntimes: PropTypes.arrayOf(Types.runtime).isRequired,
+    };
+  }
+
+  renderAdbStatus() {
+    const isUsbEnabled =
+      this.props.isAdbReady &&
+      this.props.adbAddonStatus === ADB_ADDON_STATES.INSTALLED;
+    const localizationId = isUsbEnabled
+      ? "about-debugging-sidebar-usb-enabled"
+      : "about-debugging-sidebar-usb-disabled";
+    return IconLabel(
+      {
+        level: isUsbEnabled ? ICON_LABEL_LEVEL.OK : ICON_LABEL_LEVEL.INFO,
+      },
+      Localized(
+        {
+          id: localizationId,
+        },
+        dom.span(
+          {
+            className: "qa-sidebar-usb-status",
+          },
+          localizationId
+        )
+      )
+    );
+  }
+
+  renderDevicesEmpty() {
+    return SidebarItem(
+      {},
+      Localized(
+        {
+          id: "about-debugging-sidebar-no-devices",
+        },
+        dom.aside(
+          {
+            className: "sidebar__label qa-sidebar-no-devices",
+          },
+          "No devices discovered"
+        )
+      )
+    );
+  }
+
+  renderDevices() {
+    const { networkRuntimes, usbRuntimes } = this.props;
+
+    // render a "no devices" messages when the lists are empty
+    if (!networkRuntimes.length && !usbRuntimes.length) {
+      return this.renderDevicesEmpty();
+    }
+    // render all devices otherwise
+    return [
+      ...this.renderRuntimeItems(GLOBE_ICON, networkRuntimes),
+      ...this.renderRuntimeItems(USB_ICON, usbRuntimes),
+    ];
+  }
+
+  renderRuntimeItems(icon, runtimes) {
+    const { dispatch, selectedPage, selectedRuntimeId } = this.props;
+
+    return runtimes.map(runtime => {
+      const keyId = `${runtime.type}-${runtime.id}`;
+      const runtimeHasDetails = !!runtime.runtimeDetails;
+      const isSelected =
+        selectedPage === PAGE_TYPES.RUNTIME && runtime.id === selectedRuntimeId;
+
+      let name = runtime.name;
+      if (runtime.type === RUNTIMES.USB && runtimeHasDetails) {
+        // Update the name to be same to the runtime page.
+        name = runtime.runtimeDetails.info.name;
+      }
+
+      return SidebarRuntimeItem({
+        deviceName: runtime.extra.deviceName,
+        dispatch,
+        icon,
+        key: keyId,
+        isConnected: runtimeHasDetails,
+        isConnecting: runtime.isConnecting,
+        isConnectionFailed: runtime.isConnectionFailed,
+        isConnectionNotResponding: runtime.isConnectionNotResponding,
+        isConnectionTimeout: runtime.isConnectionTimeout,
+        isSelected,
+        isUnavailable: runtime.isUnavailable,
+        isUnplugged: runtime.isUnplugged,
+        name,
+        runtimeId: runtime.id,
+      });
+    });
+  }
+
+  renderFooter() {
+    const HELP_ICON_SRC = "chrome://global/skin/icons/help.svg";
+    const SUPPORT_URL =
+      "https://firefox-source-docs.mozilla.org/devtools-user/about_colon_debugging/";
+
+    return dom.footer(
+      {
+        className: "sidebar__footer",
+      },
+      dom.ul(
+        {},
+        SidebarItem(
+          {
+            className: "sidebar-item--condensed",
+            to: SUPPORT_URL,
+          },
+          dom.span(
+            {
+              className: "sidebar__footer__support-help",
+            },
+            Localized(
+              {
+                id: "about-debugging-sidebar-support-icon",
+                attrs: {
+                  alt: true,
+                },
+              },
+              dom.img({
+                className: "sidebar__footer__icon",
+                src: HELP_ICON_SRC,
+              })
+            ),
+            Localized(
+              {
+                id: "about-debugging-sidebar-support",
+              },
+              dom.span({}, "about-debugging-sidebar-support")
+            )
+          )
+        )
+      )
+    );
+  }
+
+  render() {
+    const { dispatch, selectedPage, selectedRuntimeId, isScanningUsb } =
+      this.props;
+
+    return dom.aside(
+      {
+        className: `sidebar ${this.props.className || ""}`,
+      },
+      dom.ul(
+        {},
+        Localized(
+          { id: "about-debugging-sidebar-setup", attrs: { name: true } },
+          SidebarFixedItem({
+            dispatch,
+            icon: CONNECT_ICON,
+            isSelected: PAGE_TYPES.CONNECT === selectedPage,
+            key: PAGE_TYPES.CONNECT,
+            name: "Setup",
+            to: "/setup",
+          })
+        ),
+        Localized(
+          { id: "about-debugging-sidebar-this-firefox", attrs: { name: true } },
+          SidebarFixedItem({
+            icon: FIREFOX_ICON,
+            isSelected:
+              PAGE_TYPES.RUNTIME === selectedPage &&
+              selectedRuntimeId === RUNTIMES.THIS_FIREFOX,
+            key: RUNTIMES.THIS_FIREFOX,
+            name: "This Firefox",
+            to: `/runtime/${RUNTIMES.THIS_FIREFOX}`,
+          })
+        ),
+        SidebarItem(
+          {
+            className: "sidebar__adb-status",
+          },
+          dom.hr({ className: "separator separator--breathe" }),
+          this.renderAdbStatus()
+        ),
+        this.renderDevices(),
+        SidebarItem(
+          {
+            className: "sidebar-item--breathe sidebar__refresh-usb",
+            key: "refresh-devices",
+          },
+          RefreshDevicesButton({
+            dispatch,
+            isScanning: isScanningUsb,
+          })
+        )
+      ),
+      this.renderFooter()
+    );
+  }
+}
+
+module.exports = Sidebar;
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/SidebarFixedItem.css b/devtools/client/aboutdebugging/src/components/sidebar/SidebarFixedItem.css
new file mode 100644
index 0000000000..7345b8e80f
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/SidebarFixedItem.css
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Layout of a fixed sidebar item
+ *
+ *  +--------+----------------+
+ *  | Icon   | Name           |
+ *  +--------+----------------+
+ */
+
+.sidebar-fixed-item__container {
+  align-items: center;
+  border-radius: 2px;
+  display: grid;
+  grid-template-columns: 34px 1fr;
+  height: 100%;
+  font-size: var(--body-20-font-size);
+  font-weight: var(--body-20-font-weight);
+}
+
+.sidebar-fixed-item__icon {
+  fill: currentColor;
+  height: 24px;
+  margin-inline-end: 9px;
+  width: 24px;
+  -moz-context-properties: fill;
+}
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/SidebarFixedItem.js b/devtools/client/aboutdebugging/src/components/sidebar/SidebarFixedItem.js
new file mode 100644
index 0000000000..cf5dbab31a
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/SidebarFixedItem.js
@@ -0,0 +1,60 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  PureComponent,
+  createFactory,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const SidebarItem = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.js")
+);
+
+/**
+ * This component displays a fixed item in the Sidebar component.
+ */
+class SidebarFixedItem extends PureComponent {
+  static get propTypes() {
+    return {
+      icon: PropTypes.string.isRequired,
+      isSelected: PropTypes.bool.isRequired,
+      name: PropTypes.string.isRequired,
+      to: PropTypes.string,
+    };
+  }
+
+  render() {
+    const { icon, isSelected, name, to } = this.props;
+
+    return SidebarItem(
+      {
+        className: "sidebar-item--tall",
+        isSelected,
+        to,
+      },
+      dom.div(
+        {
+          className: "sidebar-fixed-item__container",
+        },
+        dom.img({
+          className: "sidebar-fixed-item__icon",
+          src: icon,
+        }),
+        dom.span(
+          {
+            className: "ellipsis-text",
+            title: name,
+          },
+          name
+        )
+      )
+    );
+  }
+}
+
+module.exports = SidebarFixedItem;
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.css b/devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.css
new file mode 100644
index 0000000000..3f12964012
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.css
@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+.sidebar-item {
+  color: var(--sidebar-text-color);
+  border-radius: 2px;
+  padding-inline-end: var(--category-padding);
+  padding-inline-start: var(--category-padding);
+  transition: background-color var(--category-transition-duration);
+  user-select: none;
+}
+
+.sidebar-item--tall {
+  height: var(--category-height);
+}
+
+.sidebar-item--condensed {
+  height: calc(var(--base-unit) * 9);
+}
+
+.sidebar-item__link {
+  display: block;
+  height: 100%;
+}
+
+.sidebar-item__link,
+.sidebar-item__link:hover {
+  color: inherit; /* do not apply usual link colors, but grab this element parent's */
+}
+
+.sidebar-item:not(.sidebar-item--selectable) {
+  color: var(--secondary-text-color);
+}
+
+.sidebar-item--selectable:hover {
+  background-color: var(--sidebar-background-hover);
+}
+
+.sidebar-item--selected {
+  color: var(--sidebar-selected-color);
+}
+
+.sidebar-item--breathe {
+  margin-block-start: calc(6 * var(--base-unit));
+  margin-block-end: calc(2 * var(--base-unit));
+}
+
+@media (prefers-contrast) {
+  /* Color transitions (black <-> white) look bad in high contrast */
+  .sidebar-item {
+    transition: background 0s;
+  }
+
+  .sidebar-item--selected,
+  .sidebar-item--selected:hover {
+    background-color: ButtonText;
+  }
+
+  /* `color: inherit` should not be used in high contrast mode
+     otherwise the link inherits the <a> color from ua.css */
+  .sidebar-item__link,
+  .sidebar-item__link:hover {
+    color: ButtonText;
+  }
+
+  .sidebar-item--selected .sidebar-item__link,
+  .sidebar-item--selected .sidebar-item__link:hover {
+    color: ButtonFace;
+  }
+}
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.js b/devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.js
new file mode 100644
index 0000000000..cd17d8e6bc
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.js
@@ -0,0 +1,81 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+const Link = createFactory(
+  require("resource://devtools/client/shared/vendor/react-router-dom.js").Link
+);
+
+/**
+ * This component is used as a wrapper by items in the sidebar.
+ */
+class SidebarItem extends PureComponent {
+  static get propTypes() {
+    return {
+      children: PropTypes.node.isRequired,
+      className: PropTypes.string,
+      isSelected: PropTypes.bool.isRequired,
+      to: PropTypes.string,
+    };
+  }
+
+  static get defaultProps() {
+    return {
+      isSelected: false,
+    };
+  }
+
+  renderContent() {
+    const { children, to } = this.props;
+
+    if (to) {
+      const isExternalUrl = /^http/.test(to);
+
+      return isExternalUrl
+        ? dom.a(
+            {
+              className: "sidebar-item__link undecorated-link",
+              href: to,
+              target: "_blank",
+            },
+            children
+          )
+        : Link(
+            {
+              className: "sidebar-item__link qa-sidebar-link undecorated-link",
+              to,
+            },
+            children
+          );
+    }
+
+    return children;
+  }
+
+  render() {
+    const { className, isSelected, to } = this.props;
+
+    return dom.li(
+      {
+        className:
+          "sidebar-item qa-sidebar-item" +
+          (className ? ` ${className}` : "") +
+          (isSelected
+            ? " sidebar-item--selected qa-sidebar-item-selected"
+            : "") +
+          (to ? " sidebar-item--selectable" : ""),
+      },
+      this.renderContent()
+    );
+  }
+}
+
+module.exports = SidebarItem;
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/SidebarRuntimeItem.css b/devtools/client/aboutdebugging/src/components/sidebar/SidebarRuntimeItem.css
new file mode 100644
index 0000000000..423723a27f
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/SidebarRuntimeItem.css
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Layout of a runtime sidebar item
+ *
+ *  +--------+----------------+---------------------------+
+ *  | Icon   | Runtime name   | Connect button            |
+ *  +--------+----------------+---------------------------+
+ */
+
+.sidebar-runtime-item__container {
+  box-sizing: border-box;
+  height: var(--category-height);
+  align-items: center;
+  display: grid;
+  grid-column-gap: var(--base-unit);
+  grid-template-columns: calc(var(--base-unit) * 6) 1fr auto;
+  font-size: var(--body-20-font-size);
+  font-weight: var(--body-20-font-weight);
+}
+
+.sidebar-runtime-item__icon {
+  fill: currentColor;
+  -moz-context-properties: fill;
+}
+
+.sidebar-runtime-item__runtime {
+  line-height: 1;
+}
+
+.sidebar-runtime-item__runtime__details {
+  font-size: var(--caption-10-font-size);
+  font-weight: var(--caption-10-font-weight);
+  line-height: 1.2;
+}
+
+.sidebar-runtime-item__message:first-of-type {
+  margin-block-start: calc(var(--base-unit) * -1);
+}
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/SidebarRuntimeItem.js b/devtools/client/aboutdebugging/src/components/sidebar/SidebarRuntimeItem.js
new file mode 100644
index 0000000000..a5c5fe6d55
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/SidebarRuntimeItem.js
@@ -0,0 +1,216 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const dom = require("resource://devtools/client/shared/vendor/react-dom-factories.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FluentReact = require("resource://devtools/client/shared/vendor/fluent-react.js");
+const Localized = createFactory(FluentReact.Localized);
+
+const Message = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/shared/Message.js")
+);
+const SidebarItem = createFactory(
+  require("resource://devtools/client/aboutdebugging/src/components/sidebar/SidebarItem.js")
+);
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+const {
+  MESSAGE_LEVEL,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This component displays a runtime item of the Sidebar component.
+ */
+class SidebarRuntimeItem extends PureComponent {
+  static get propTypes() {
+    return {
+      deviceName: PropTypes.string,
+      dispatch: PropTypes.func.isRequired,
+      // Provided by wrapping the component with FluentReact.withLocalization.
+      getString: PropTypes.func.isRequired,
+      icon: PropTypes.string.isRequired,
+      isConnected: PropTypes.bool.isRequired,
+      isConnecting: PropTypes.bool.isRequired,
+      isConnectionFailed: PropTypes.bool.isRequired,
+      isConnectionNotResponding: PropTypes.bool.isRequired,
+      isConnectionTimeout: PropTypes.bool.isRequired,
+      isSelected: PropTypes.bool.isRequired,
+      isUnavailable: PropTypes.bool.isRequired,
+      isUnplugged: PropTypes.bool.isRequired,
+      name: PropTypes.string.isRequired,
+      runtimeId: PropTypes.string.isRequired,
+    };
+  }
+
+  renderConnectButton() {
+    const { isConnecting } = this.props;
+    const localizationId = isConnecting
+      ? "about-debugging-sidebar-item-connect-button-connecting"
+      : "about-debugging-sidebar-item-connect-button";
+    return Localized(
+      {
+        id: localizationId,
+      },
+      dom.button(
+        {
+          className: "default-button default-button--micro qa-connect-button",
+          disabled: isConnecting,
+          onClick: () => {
+            const { dispatch, runtimeId } = this.props;
+            dispatch(Actions.connectRuntime(runtimeId));
+          },
+        },
+        localizationId
+      )
+    );
+  }
+
+  renderMessage(flag, level, localizationId, className) {
+    if (!flag) {
+      return null;
+    }
+
+    return Message(
+      {
+        level,
+        className: `${className} sidebar-runtime-item__message`,
+        isCloseable: true,
+      },
+      Localized(
+        {
+          id: localizationId,
+        },
+        dom.p({ className: "word-wrap-anywhere" }, localizationId)
+      )
+    );
+  }
+
+  renderName() {
+    const { deviceName, getString, isUnavailable, isUnplugged, name } =
+      this.props;
+
+    let displayName, qaClassName;
+    if (isUnplugged) {
+      displayName = getString("about-debugging-sidebar-runtime-item-unplugged");
+      qaClassName = "qa-runtime-item-unplugged";
+    } else if (isUnavailable) {
+      displayName = getString(
+        "about-debugging-sidebar-runtime-item-waiting-for-browser"
+      );
+      qaClassName = "qa-runtime-item-waiting-for-browser";
+    } else {
+      displayName = name;
+      qaClassName = "qa-runtime-item-standard";
+    }
+
+    const localizationId = deviceName
+      ? "about-debugging-sidebar-runtime-item-name"
+      : "about-debugging-sidebar-runtime-item-name-no-device";
+
+    const className = "ellipsis-text sidebar-runtime-item__runtime";
+
+    function renderWithDevice() {
+      return dom.span(
+        {
+          className,
+          title: localizationId,
+        },
+        deviceName,
+        dom.br({}),
+        dom.span(
+          {
+            className: `sidebar-runtime-item__runtime__details ${qaClassName}`,
+          },
+          displayName
+        )
+      );
+    }
+
+    function renderNoDevice() {
+      return dom.span(
+        {
+          className,
+          title: localizationId,
+        },
+        displayName
+      );
+    }
+
+    return Localized(
+      {
+        id: localizationId,
+        attrs: { title: true },
+        $deviceName: deviceName,
+        $displayName: displayName,
+      },
+      deviceName ? renderWithDevice() : renderNoDevice()
+    );
+  }
+
+  render() {
+    const {
+      getString,
+      icon,
+      isConnected,
+      isConnectionFailed,
+      isConnectionTimeout,
+      isConnectionNotResponding,
+      isSelected,
+      isUnavailable,
+      runtimeId,
+    } = this.props;
+
+    const connectionStatus = isConnected
+      ? getString("aboutdebugging-sidebar-runtime-connection-status-connected")
+      : getString(
+          "aboutdebugging-sidebar-runtime-connection-status-disconnected"
+        );
+
+    return SidebarItem(
+      {
+        isSelected,
+        to: isConnected ? `/runtime/${encodeURIComponent(runtimeId)}` : null,
+      },
+      dom.section(
+        {
+          className: "sidebar-runtime-item__container",
+        },
+        dom.img({
+          className: "sidebar-runtime-item__icon ",
+          src: icon,
+          alt: connectionStatus,
+          title: connectionStatus,
+        }),
+        this.renderName(),
+        !isUnavailable && !isConnected ? this.renderConnectButton() : null
+      ),
+      this.renderMessage(
+        isConnectionFailed,
+        MESSAGE_LEVEL.ERROR,
+        "about-debugging-sidebar-item-connect-button-connection-failed",
+        "qa-connection-error"
+      ),
+      this.renderMessage(
+        isConnectionTimeout,
+        MESSAGE_LEVEL.ERROR,
+        "about-debugging-sidebar-item-connect-button-connection-timeout",
+        "qa-connection-timeout"
+      ),
+      this.renderMessage(
+        isConnectionNotResponding,
+        MESSAGE_LEVEL.WARNING,
+        "about-debugging-sidebar-item-connect-button-connection-not-responding",
+        "qa-connection-not-responding"
+      )
+    );
+  }
+}
+
+module.exports = FluentReact.withLocalization(SidebarRuntimeItem);
diff --git a/devtools/client/aboutdebugging/src/components/sidebar/moz.build b/devtools/client/aboutdebugging/src/components/sidebar/moz.build
new file mode 100644
index 0000000000..081ea2a848
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/components/sidebar/moz.build
@@ -0,0 +1,11 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "RefreshDevicesButton.js",
+    "Sidebar.js",
+    "SidebarFixedItem.js",
+    "SidebarItem.js",
+    "SidebarRuntimeItem.js",
+)
diff --git a/devtools/client/aboutdebugging/src/constants.js b/devtools/client/aboutdebugging/src/constants.js
new file mode 100644
index 0000000000..fa0b847a32
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/constants.js
@@ -0,0 +1,185 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  CONNECTION_TYPES,
+  DEBUG_TARGET_TYPES,
+} = require("resource://devtools/client/shared/remote-debugging/constants.js");
+
+const actionTypes = {
+  ADB_ADDON_INSTALL_START: "ADB_ADDON_INSTALL_START",
+  ADB_ADDON_INSTALL_SUCCESS: "ADB_ADDON_INSTALL_SUCCESS",
+  ADB_ADDON_INSTALL_FAILURE: "ADB_ADDON_INSTALL_FAILURE",
+  ADB_ADDON_UNINSTALL_START: "ADB_ADDON_UNINSTALL_START",
+  ADB_ADDON_UNINSTALL_SUCCESS: "ADB_ADDON_UNINSTALL_SUCCESS",
+  ADB_ADDON_UNINSTALL_FAILURE: "ADB_ADDON_UNINSTALL_FAILURE",
+  ADB_ADDON_STATUS_UPDATED: "ADB_ADDON_STATUS_UPDATED",
+  ADB_READY_UPDATED: "ADB_READY_UPDATED",
+  CONNECT_RUNTIME_CANCEL: "CONNECT_RUNTIME_CANCEL",
+  CONNECT_RUNTIME_FAILURE: "CONNECT_RUNTIME_FAILURE",
+  CONNECT_RUNTIME_NOT_RESPONDING: "CONNECT_RUNTIME_NOT_RESPONDING",
+  CONNECT_RUNTIME_START: "CONNECT_RUNTIME_START",
+  CONNECT_RUNTIME_SUCCESS: "CONNECT_RUNTIME_SUCCESS",
+  DEBUG_TARGET_COLLAPSIBILITY_UPDATED: "DEBUG_TARGET_COLLAPSIBILITY_UPDATED",
+  DISCONNECT_RUNTIME_FAILURE: "DISCONNECT_RUNTIME_FAILURE",
+  DISCONNECT_RUNTIME_START: "DISCONNECT_RUNTIME_START",
+  DISCONNECT_RUNTIME_SUCCESS: "DISCONNECT_RUNTIME_SUCCESS",
+  EXTENSION_BGSCRIPT_STATUS_UPDATED: "EXTENSION_BGSCRIPT_STATUS_UPDATED",
+  HIDE_PROFILER_DIALOG: "HIDE_PROFILER_DIALOG",
+  SWITCH_PROFILER_CONTEXT: "SWITCH_PROFILER_CONTEXT",
+  NETWORK_LOCATIONS_UPDATE_FAILURE: "NETWORK_LOCATIONS_UPDATE_FAILURE",
+  NETWORK_LOCATIONS_UPDATE_START: "NETWORK_LOCATIONS_UPDATE_START",
+  NETWORK_LOCATIONS_UPDATE_SUCCESS: "NETWORK_LOCATIONS_UPDATE_SUCCESS",
+  REMOTE_RUNTIMES_UPDATED: "REMOTE_RUNTIMES_UPDATED",
+  REQUEST_EXTENSIONS_FAILURE: "REQUEST_EXTENSIONS_FAILURE",
+  REQUEST_EXTENSIONS_START: "REQUEST_EXTENSIONS_START",
+  REQUEST_EXTENSIONS_SUCCESS: "REQUEST_EXTENSIONS_SUCCESS",
+  REQUEST_PROCESSES_FAILURE: "REQUEST_PROCESSES_FAILURE",
+  REQUEST_PROCESSES_START: "REQUEST_PROCESSES_START",
+  REQUEST_PROCESSES_SUCCESS: "REQUEST_PROCESSES_SUCCESS",
+  REQUEST_TABS_FAILURE: "REQUEST_TABS_FAILURE",
+  REQUEST_TABS_START: "REQUEST_TABS_START",
+  REQUEST_TABS_SUCCESS: "REQUEST_TABS_SUCCESS",
+  REQUEST_WORKERS_FAILURE: "REQUEST_WORKERS_FAILURE",
+  REQUEST_WORKERS_START: "REQUEST_WORKERS_START",
+  REQUEST_WORKERS_SUCCESS: "REQUEST_WORKERS_SUCCESS",
+  SELECT_PAGE_FAILURE: "SELECT_PAGE_FAILURE",
+  SELECT_PAGE_START: "SELECT_PAGE_START",
+  SELECT_PAGE_SUCCESS: "SELECT_PAGE_SUCCESS",
+  SELECTED_RUNTIME_ID_UPDATED: "SELECTED_RUNTIME_ID_UPDATED",
+  SHOW_PROFILER_DIALOG: "SHOW_PROFILER_DIALOG",
+  TELEMETRY_RECORD: "TELEMETRY_RECORD",
+  TEMPORARY_EXTENSION_INSTALL_FAILURE: "TEMPORARY_EXTENSION_INSTALL_FAILURE",
+  TEMPORARY_EXTENSION_INSTALL_START: "TEMPORARY_EXTENSION_INSTALL_START",
+  TEMPORARY_EXTENSION_INSTALL_SUCCESS: "TEMPORARY_EXTENSION_INSTALL_SUCCESS",
+  TEMPORARY_EXTENSION_RELOAD_FAILURE: "TEMPORARY_EXTENSION_RELOAD_FAILURE",
+  TEMPORARY_EXTENSION_RELOAD_START: "TEMPORARY_EXTENSION_RELOAD_START",
+  TEMPORARY_EXTENSION_RELOAD_SUCCESS: "TEMPORARY_EXTENSION_RELOAD_SUCCESS",
+  TERMINATE_EXTENSION_BGSCRIPT_FAILURE: "TERMINATE_EXTENSION_BGSCRIPT_FAILURE",
+  TERMINATE_EXTENSION_BGSCRIPT_START: "TERMINATE_EXTENSION_BGSCRIPT_START",
+  TERMINATE_EXTENSION_BGSCRIPT_SUCCESS: "TERMINATE_EXTENSION_BGSCRIPT_SUCCESS",
+  THIS_FIREFOX_RUNTIME_CREATED: "THIS_FIREFOX_RUNTIME_CREATED",
+  UNWATCH_RUNTIME_FAILURE: "UNWATCH_RUNTIME_FAILURE",
+  UNWATCH_RUNTIME_START: "UNWATCH_RUNTIME_START",
+  UNWATCH_RUNTIME_SUCCESS: "UNWATCH_RUNTIME_SUCCESS",
+  UPDATE_CONNECTION_PROMPT_SETTING_FAILURE:
+    "UPDATE_CONNECTION_PROMPT_SETTING_FAILURE",
+  UPDATE_CONNECTION_PROMPT_SETTING_START:
+    "UPDATE_CONNECTION_PROMPT_SETTING_START",
+  UPDATE_CONNECTION_PROMPT_SETTING_SUCCESS:
+    "UPDATE_CONNECTION_PROMPT_SETTING_SUCCESS",
+  USB_RUNTIMES_SCAN_START: "USB_RUNTIMES_SCAN_START",
+  USB_RUNTIMES_SCAN_SUCCESS: "USB_RUNTIMES_SCAN_SUCCESS",
+  WATCH_RUNTIME_FAILURE: "WATCH_RUNTIME_FAILURE",
+  WATCH_RUNTIME_START: "WATCH_RUNTIME_START",
+  WATCH_RUNTIME_SUCCESS: "WATCH_RUNTIME_SUCCESS",
+};
+
+const DEBUG_TARGETS = DEBUG_TARGET_TYPES;
+
+const DEBUG_TARGET_PANE = {
+  INSTALLED_EXTENSION: "installedExtension",
+  PROCESSES: "processes",
+  OTHER_WORKER: "otherWorker",
+  SERVICE_WORKER: "serviceWorker",
+  SHARED_WORKER: "sharedWorker",
+  TAB: "tab",
+  TEMPORARY_EXTENSION: "temporaryExtension",
+};
+
+const ICON_LABEL_LEVEL = {
+  INFO: "info",
+  OK: "ok",
+};
+
+const MESSAGE_LEVEL = {
+  ERROR: "error",
+  INFO: "info",
+  WARNING: "warning",
+};
+
+const PAGE_TYPES = {
+  RUNTIME: "runtime",
+  CONNECT: "connect",
+};
+
+const PREFERENCES = {
+  // Preference that drives the display of the "Tabs" category on This Firefox.
+  LOCAL_TAB_DEBUGGING_ENABLED: "devtools.aboutdebugging.local-tab-debugging",
+  // Preference that drives the display of the "Processes" debug target category.
+  PROCESS_DEBUGGING_ENABLED: "devtools.aboutdebugging.process-debugging",
+  // Preference that drives the display of hidden & system addons in about:debugging.
+  SHOW_HIDDEN_ADDONS: "devtools.aboutdebugging.showHiddenAddons",
+  // Preference to store the last path used for loading a temporary extension.
+  TEMPORARY_EXTENSION_PATH: "devtools.aboutdebugging.tmpExtDirPath",
+  // Preference that disables installing extensions when set to false.
+  XPINSTALL_ENABLED: "xpinstall.enabled",
+};
+
+const RUNTIME_PREFERENCE = {
+  CONNECTION_PROMPT: "devtools.debugger.prompt-connection",
+  PERMANENT_PRIVATE_BROWSING: "browser.privatebrowsing.autostart",
+  SERVICE_WORKERS_ENABLED: "dom.serviceWorkers.enabled",
+};
+
+const RUNTIMES = {
+  NETWORK: CONNECTION_TYPES.NETWORK,
+  THIS_FIREFOX: CONNECTION_TYPES.THIS_FIREFOX,
+  USB: CONNECTION_TYPES.USB,
+};
+
+const SERVICE_WORKER_FETCH_STATES = {
+  LISTENING: "LISTENING",
+  NOT_LISTENING: "NOT_LISTENING",
+};
+
+const SERVICE_WORKER_STATUSES = {
+  RUNNING: "RUNNING",
+  REGISTERING: "REGISTERING",
+  STOPPED: "STOPPED",
+};
+
+const USB_STATES = {
+  DISABLED_USB: "DISABLED_USB",
+  ENABLED_USB: "ENABLED_USB",
+  UPDATING_USB: "UPDATING_USB",
+};
+
+const EXTENSION_BGSCRIPT_STATUSES = {
+  RUNNING: "RUNNING",
+  STOPPED: "STOPPED",
+};
+
+/**
+ * These constants reference the performance-new's concept of a PageContext.
+ * These are defined in devtools/client/performance-new/@types/perf.d.ts
+ * about:debugging only uses the remote variants of the PageContexts.
+ */
+const PROFILER_PAGE_CONTEXT = {
+  DEVTOOLS_REMOTE: "devtools-remote",
+  ABOUTPROFILING_REMOTE: "aboutprofiling-remote",
+};
+
+// flatten constants
+module.exports = Object.assign(
+  {},
+  {
+    DEBUG_TARGETS,
+    DEBUG_TARGET_PANE,
+    EXTENSION_BGSCRIPT_STATUSES,
+    ICON_LABEL_LEVEL,
+    MESSAGE_LEVEL,
+    PAGE_TYPES,
+    PREFERENCES,
+    RUNTIME_PREFERENCE,
+    RUNTIMES,
+    SERVICE_WORKER_FETCH_STATES,
+    SERVICE_WORKER_STATUSES,
+    USB_STATES,
+    PROFILER_PAGE_CONTEXT,
+  },
+  actionTypes
+);
diff --git a/devtools/client/aboutdebugging/src/create-store.js b/devtools/client/aboutdebugging/src/create-store.js
new file mode 100644
index 0000000000..93fd240b00
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/create-store.js
@@ -0,0 +1,78 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  applyMiddleware,
+  createStore,
+} = require("resource://devtools/client/shared/vendor/redux.js");
+const {
+  thunk,
+} = require("resource://devtools/client/shared/redux/middleware/thunk.js");
+const {
+  waitUntilService,
+} = require("resource://devtools/client/shared/redux/middleware/wait-service.js");
+
+const rootReducer = require("resource://devtools/client/aboutdebugging/src/reducers/index.js");
+const {
+  DebugTargetsState,
+} = require("resource://devtools/client/aboutdebugging/src/reducers/debug-targets-state.js");
+const {
+  RuntimesState,
+} = require("resource://devtools/client/aboutdebugging/src/reducers/runtimes-state.js");
+const {
+  UiState,
+} = require("resource://devtools/client/aboutdebugging/src/reducers/ui-state.js");
+const debugTargetListenerMiddleware = require("resource://devtools/client/aboutdebugging/src/middleware/debug-target-listener.js");
+const errorLoggingMiddleware = require("resource://devtools/client/aboutdebugging/src/middleware/error-logging.js");
+const eventRecordingMiddleware = require("resource://devtools/client/aboutdebugging/src/middleware/event-recording.js");
+const extensionComponentDataMiddleware = require("resource://devtools/client/aboutdebugging/src/middleware/extension-component-data.js");
+const processComponentDataMiddleware = require("resource://devtools/client/aboutdebugging/src/middleware/process-component-data.js");
+const tabComponentDataMiddleware = require("resource://devtools/client/aboutdebugging/src/middleware/tab-component-data.js");
+const workerComponentDataMiddleware = require("resource://devtools/client/aboutdebugging/src/middleware/worker-component-data.js");
+const {
+  getDebugTargetCollapsibilities,
+} = require("resource://devtools/client/aboutdebugging/src/modules/debug-target-collapsibilities.js");
+const {
+  getNetworkLocations,
+} = require("resource://devtools/client/aboutdebugging/src/modules/network-locations.js");
+
+const {
+  PREFERENCES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+function configureStore() {
+  const initialState = {
+    debugTargets: new DebugTargetsState(),
+    runtimes: new RuntimesState(),
+    ui: getUiState(),
+  };
+
+  const middleware = applyMiddleware(
+    thunk(),
+    debugTargetListenerMiddleware,
+    errorLoggingMiddleware,
+    eventRecordingMiddleware,
+    extensionComponentDataMiddleware,
+    processComponentDataMiddleware,
+    tabComponentDataMiddleware,
+    workerComponentDataMiddleware,
+    waitUntilService
+  );
+
+  return createStore(rootReducer, initialState, middleware);
+}
+
+function getUiState() {
+  const collapsibilities = getDebugTargetCollapsibilities();
+  const locations = getNetworkLocations();
+  const showHiddenAddons = Services.prefs.getBoolPref(
+    PREFERENCES.SHOW_HIDDEN_ADDONS,
+    false
+  );
+  return new UiState(locations, collapsibilities, showHiddenAddons);
+}
+
+exports.configureStore = configureStore;
diff --git a/devtools/client/aboutdebugging/src/middleware/debug-target-listener.js b/devtools/client/aboutdebugging/src/middleware/debug-target-listener.js
new file mode 100644
index 0000000000..655e667a6d
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/middleware/debug-target-listener.js
@@ -0,0 +1,111 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  EXTENSION_BGSCRIPT_STATUSES,
+  EXTENSION_BGSCRIPT_STATUS_UPDATED,
+  UNWATCH_RUNTIME_START,
+  WATCH_RUNTIME_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const Actions = require("resource://devtools/client/aboutdebugging/src/actions/index.js");
+
+const RootResourceCommand = require("resource://devtools/shared/commands/root-resource/root-resource-command.js");
+
+function debugTargetListenerMiddleware(store) {
+  const onExtensionsUpdated = () => {
+    store.dispatch(Actions.requestExtensions());
+  };
+
+  const onTabsUpdated = () => {
+    store.dispatch(Actions.requestTabs());
+  };
+
+  const onWorkersUpdated = () => {
+    store.dispatch(Actions.requestWorkers());
+  };
+
+  let rootResourceCommand;
+
+  function onExtensionsBackgroundScriptStatusAvailable(resources) {
+    for (const resource of resources) {
+      const backgroundScriptStatus = resource.payload.isRunning
+        ? EXTENSION_BGSCRIPT_STATUSES.RUNNING
+        : EXTENSION_BGSCRIPT_STATUSES.STOPPED;
+
+      store.dispatch({
+        type: EXTENSION_BGSCRIPT_STATUS_UPDATED,
+        id: resource.payload.addonId,
+        backgroundScriptStatus,
+      });
+    }
+  }
+
+  return next => async action => {
+    switch (action.type) {
+      case WATCH_RUNTIME_SUCCESS: {
+        const { runtime } = action;
+        const { clientWrapper } = runtime.runtimeDetails;
+
+        rootResourceCommand = clientWrapper.createRootResourceCommand();
+
+        // Watch extensions background script status updates.
+        await rootResourceCommand
+          .watchResources(
+            [RootResourceCommand.TYPES.EXTENSIONS_BGSCRIPT_STATUS],
+            { onAvailable: onExtensionsBackgroundScriptStatusAvailable }
+          )
+          .catch(e => {
+            // Log an error if watching this resource rejects (e.g. if
+            // the promise was not resolved yet when about:debugging tab
+            // or the RDP connection to a remote target has been closed).
+            console.error(e);
+          });
+
+        // Tabs
+        clientWrapper.on("tabListChanged", onTabsUpdated);
+
+        // Addons
+        clientWrapper.on("addonListChanged", onExtensionsUpdated);
+
+        // Workers
+        clientWrapper.on("workersUpdated", onWorkersUpdated);
+        break;
+      }
+      case UNWATCH_RUNTIME_START: {
+        const { runtime } = action;
+        const { clientWrapper } = runtime.runtimeDetails;
+
+        // Stop watching extensions background script status updates.
+        try {
+          rootResourceCommand?.unwatchResources(
+            [RootResourceCommand.TYPES.EXTENSIONS_BGSCRIPT_STATUS],
+            { onAvailable: onExtensionsBackgroundScriptStatusAvailable }
+          );
+        } catch (e) {
+          // Log an error  if watching this resource rejects (e.g. if
+          // the promise was not resolved yet when about:debugging tab
+          // or the RDP connection to a remote target has been closed).
+          console.error(e);
+        }
+
+        // Tabs
+        clientWrapper.off("tabListChanged", onTabsUpdated);
+
+        // Addons
+        clientWrapper.off("addonListChanged", onExtensionsUpdated);
+
+        // Workers
+        clientWrapper.off("workersUpdated", onWorkersUpdated);
+        break;
+      }
+    }
+
+    return next(action);
+  };
+}
+
+module.exports = debugTargetListenerMiddleware;
diff --git a/devtools/client/aboutdebugging/src/middleware/error-logging.js b/devtools/client/aboutdebugging/src/middleware/error-logging.js
new file mode 100644
index 0000000000..fd04f34b76
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/middleware/error-logging.js
@@ -0,0 +1,35 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Error logging middleware that will forward all actions that contain an error property
+ * to the console.
+ */
+function errorLoggingMiddleware() {
+  return next => action => {
+    if (action.error) {
+      const { error } = action;
+      if (error.message) {
+        console.error(`[ACTION FAILED] ${action.type}: ${error.message}`);
+      } else if (typeof error === "string") {
+        // All failure actions should dispatch an error object instead of a message.
+        // We allow some flexibility to still provide some error logging.
+        console.error(`[ACTION FAILED] ${action.type}: ${error}`);
+        console.error(
+          `[ACTION FAILED] ${action.type} should dispatch the error object!`
+        );
+      }
+
+      if (error.stack) {
+        console.error(error.stack);
+      }
+    }
+
+    return next(action);
+  };
+}
+
+module.exports = errorLoggingMiddleware;
diff --git a/devtools/client/aboutdebugging/src/middleware/event-recording.js b/devtools/client/aboutdebugging/src/middleware/event-recording.js
new file mode 100644
index 0000000000..f926100b8b
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/middleware/event-recording.js
@@ -0,0 +1,268 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const Telemetry = require("resource://devtools/client/shared/telemetry.js");
+loader.lazyGetter(
+  this,
+  "telemetry",
+  () => new Telemetry({ useSessionId: true })
+);
+
+const {
+  CONNECT_RUNTIME_CANCEL,
+  CONNECT_RUNTIME_FAILURE,
+  CONNECT_RUNTIME_NOT_RESPONDING,
+  CONNECT_RUNTIME_START,
+  CONNECT_RUNTIME_SUCCESS,
+  DISCONNECT_RUNTIME_SUCCESS,
+  REMOTE_RUNTIMES_UPDATED,
+  RUNTIMES,
+  SELECT_PAGE_SUCCESS,
+  SHOW_PROFILER_DIALOG,
+  TELEMETRY_RECORD,
+  UPDATE_CONNECTION_PROMPT_SETTING_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const {
+  findRuntimeById,
+  getAllRuntimes,
+  getCurrentRuntime,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js");
+
+function recordEvent(method, details) {
+  telemetry.recordEvent(method, "aboutdebugging", null, details);
+
+  // For close and open events, also ping the regular telemetry helpers used
+  // for all DevTools UIs.
+  if (method === "open_adbg") {
+    telemetry.toolOpened("aboutdebugging", window.AboutDebugging);
+  } else if (method === "close_adbg") {
+    // XXX: Note that aboutdebugging has no histogram created for
+    // TIME_ACTIVE_SECOND, so calling toolClosed will not actually
+    // record anything.
+    telemetry.toolClosed("aboutdebugging", window.AboutDebugging);
+  }
+}
+
+const telemetryRuntimeIds = new Map();
+// Create an anonymous id that will allow to track all events related to a runtime without
+// leaking personal data related to this runtime.
+function getTelemetryRuntimeId(id) {
+  if (!telemetryRuntimeIds.has(id)) {
+    const randomId = (Math.random() * 100000) | 0;
+    telemetryRuntimeIds.set(id, "runtime-" + randomId);
+  }
+  return telemetryRuntimeIds.get(id);
+}
+
+function getCurrentRuntimeIdForTelemetry(store) {
+  const id = getCurrentRuntime(store.getState().runtimes).id;
+  return getTelemetryRuntimeId(id);
+}
+
+function getRuntimeEventExtras(runtime) {
+  const { extra, runtimeDetails } = runtime;
+
+  // deviceName can be undefined for non-usb devices, but we should not log "undefined".
+  const deviceName = extra?.deviceName || "";
+  const runtimeShortName = runtime.type === RUNTIMES.USB ? runtime.name : "";
+  const runtimeName = runtimeDetails?.info.name || "";
+  return {
+    connection_type: runtime.type,
+    device_name: deviceName,
+    runtime_id: getTelemetryRuntimeId(runtime.id),
+    runtime_name: runtimeName || runtimeShortName,
+  };
+}
+
+function onConnectRuntimeSuccess(action, store) {
+  if (action.runtime.type === RUNTIMES.THIS_FIREFOX) {
+    // Only record connection and disconnection events for remote runtimes.
+    return;
+  }
+  // When we just connected to a runtime, the runtimeDetails are not in the store yet,
+  // so we merge it here to retrieve the expected telemetry data.
+  const storeRuntime = findRuntimeById(
+    action.runtime.id,
+    store.getState().runtimes
+  );
+  const runtime = Object.assign({}, storeRuntime, {
+    runtimeDetails: action.runtime.runtimeDetails,
+  });
+  const extras = Object.assign({}, getRuntimeEventExtras(runtime), {
+    runtime_os: action.runtime.runtimeDetails.info.os,
+    runtime_version: action.runtime.runtimeDetails.info.version,
+  });
+  recordEvent("runtime_connected", extras);
+}
+
+function onDisconnectRuntimeSuccess(action, store) {
+  const runtime = findRuntimeById(action.runtime.id, store.getState().runtimes);
+  if (runtime.type === RUNTIMES.THIS_FIREFOX) {
+    // Only record connection and disconnection events for remote runtimes.
+    return;
+  }
+
+  recordEvent("runtime_disconnected", getRuntimeEventExtras(runtime));
+}
+
+function onRemoteRuntimesUpdated(action, store) {
+  // Compare new runtimes with the existing runtimes to detect if runtimes, devices
+  // have been added or removed.
+  const newRuntimes = action.runtimes;
+  const allRuntimes = getAllRuntimes(store.getState().runtimes);
+  const oldRuntimes = allRuntimes.filter(r => r.type === action.runtimeType);
+
+  // Check if all the old runtimes and devices are still available in the updated
+  // array.
+  for (const oldRuntime of oldRuntimes) {
+    const runtimeRemoved = newRuntimes.every(r => r.id !== oldRuntime.id);
+    if (runtimeRemoved && !oldRuntime.isUnplugged) {
+      recordEvent("runtime_removed", getRuntimeEventExtras(oldRuntime));
+    }
+  }
+
+  // Using device names as unique IDs is inaccurate. See Bug 1544582.
+  const oldDeviceNames = new Set(oldRuntimes.map(r => r.extra.deviceName));
+  for (const oldDeviceName of oldDeviceNames) {
+    const newRuntime = newRuntimes.find(
+      r => r.extra.deviceName === oldDeviceName
+    );
+    const oldRuntime = oldRuntimes.find(
+      r => r.extra.deviceName === oldDeviceName
+    );
+    const isUnplugged = newRuntime?.isUnplugged && !oldRuntime.isUnplugged;
+    if (oldDeviceName && (!newRuntime || isUnplugged)) {
+      recordEvent("device_removed", {
+        connection_type: action.runtimeType,
+        device_name: oldDeviceName,
+      });
+    }
+  }
+
+  // Check if the new runtimes and devices were already available in the existing
+  // array.
+  for (const newRuntime of newRuntimes) {
+    const runtimeAdded = oldRuntimes.every(r => r.id !== newRuntime.id);
+    if (runtimeAdded && !newRuntime.isUnplugged) {
+      recordEvent("runtime_added", getRuntimeEventExtras(newRuntime));
+    }
+  }
+
+  // Using device names as unique IDs is inaccurate. See Bug 1544582.
+  const newDeviceNames = new Set(newRuntimes.map(r => r.extra.deviceName));
+  for (const newDeviceName of newDeviceNames) {
+    const newRuntime = newRuntimes.find(
+      r => r.extra.deviceName === newDeviceName
+    );
+    const oldRuntime = oldRuntimes.find(
+      r => r.extra.deviceName === newDeviceName
+    );
+    const isPlugged = oldRuntime?.isUnplugged && !newRuntime.isUnplugged;
+
+    if (newDeviceName && (!oldRuntime || isPlugged)) {
+      recordEvent("device_added", {
+        connection_type: action.runtimeType,
+        device_name: newDeviceName,
+      });
+    }
+  }
+}
+
+function recordConnectionAttempt(connectionId, runtimeId, status, store) {
+  const runtime = findRuntimeById(runtimeId, store.getState().runtimes);
+  if (runtime.type === RUNTIMES.THIS_FIREFOX) {
+    // Only record connection_attempt events for remote runtimes.
+    return;
+  }
+
+  recordEvent("connection_attempt", {
+    connection_id: connectionId,
+    connection_type: runtime.type,
+    runtime_id: getTelemetryRuntimeId(runtimeId),
+    status,
+  });
+}
+
+/**
+ * This middleware will record events to telemetry for some specific actions.
+ */
+function eventRecordingMiddleware(store) {
+  return next => action => {
+    switch (action.type) {
+      case CONNECT_RUNTIME_CANCEL:
+        recordConnectionAttempt(
+          action.connectionId,
+          action.id,
+          "cancelled",
+          store
+        );
+        break;
+      case CONNECT_RUNTIME_FAILURE:
+        recordConnectionAttempt(
+          action.connectionId,
+          action.id,
+          "failed",
+          store
+        );
+        break;
+      case CONNECT_RUNTIME_NOT_RESPONDING:
+        recordConnectionAttempt(
+          action.connectionId,
+          action.id,
+          "not responding",
+          store
+        );
+        break;
+      case CONNECT_RUNTIME_START:
+        recordConnectionAttempt(action.connectionId, action.id, "start", store);
+        break;
+      case CONNECT_RUNTIME_SUCCESS:
+        recordConnectionAttempt(
+          action.connectionId,
+          action.runtime.id,
+          "success",
+          store
+        );
+        onConnectRuntimeSuccess(action, store);
+        break;
+      case DISCONNECT_RUNTIME_SUCCESS:
+        onDisconnectRuntimeSuccess(action, store);
+        break;
+      case REMOTE_RUNTIMES_UPDATED:
+        onRemoteRuntimesUpdated(action, store);
+        break;
+      case SELECT_PAGE_SUCCESS:
+        recordEvent("select_page", { page_type: action.page });
+        break;
+      case SHOW_PROFILER_DIALOG:
+        recordEvent("show_profiler", {
+          runtime_id: getCurrentRuntimeIdForTelemetry(store),
+        });
+        break;
+      case TELEMETRY_RECORD:
+        const { method, details } = action;
+        if (method) {
+          recordEvent(method, details);
+        } else {
+          console.error(
+            `[RECORD EVENT FAILED] ${action.type}: no "method" property`
+          );
+        }
+        break;
+      case UPDATE_CONNECTION_PROMPT_SETTING_SUCCESS:
+        recordEvent("update_conn_prompt", {
+          prompt_enabled: `${action.connectionPromptEnabled}`,
+          runtime_id: getCurrentRuntimeIdForTelemetry(store),
+        });
+        break;
+    }
+
+    return next(action);
+  };
+}
+
+module.exports = eventRecordingMiddleware;
diff --git a/devtools/client/aboutdebugging/src/middleware/extension-component-data.js b/devtools/client/aboutdebugging/src/middleware/extension-component-data.js
new file mode 100644
index 0000000000..5987f36398
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/middleware/extension-component-data.js
@@ -0,0 +1,84 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  DEBUG_TARGETS,
+  REQUEST_EXTENSIONS_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const {
+  getExtensionUuid,
+  parseFileUri,
+} = require("resource://devtools/client/aboutdebugging/src/modules/extensions-helper.js");
+
+/**
+ * This middleware converts extensions object that get from DevToolsClient.listAddons()
+ * to data which is used in DebugTargetItem.
+ */
+const extensionComponentDataMiddleware = store => next => action => {
+  switch (action.type) {
+    case REQUEST_EXTENSIONS_SUCCESS: {
+      action.installedExtensions = toComponentData(action.installedExtensions);
+      action.temporaryExtensions = toComponentData(action.temporaryExtensions);
+      break;
+    }
+  }
+
+  return next(action);
+};
+
+function getFilePath(extension) {
+  // Only show file system paths, and only for temporarily installed add-ons.
+  if (
+    !extension.temporarilyInstalled ||
+    !extension.url ||
+    !extension.url.startsWith("file://")
+  ) {
+    return null;
+  }
+
+  return parseFileUri(extension.url);
+}
+
+function toComponentData(extensions) {
+  return extensions.map(extension => {
+    const type = DEBUG_TARGETS.EXTENSION;
+    const {
+      actor,
+      backgroundScriptStatus,
+      iconDataURL,
+      iconURL,
+      id,
+      manifestURL,
+      name,
+      persistentBackgroundScript,
+      warnings,
+    } = extension;
+    const icon =
+      iconDataURL ||
+      iconURL ||
+      "chrome://mozapps/skin/extensions/extensionGeneric.svg";
+    const location = getFilePath(extension);
+    const uuid = getExtensionUuid(extension);
+    return {
+      name,
+      icon,
+      id,
+      type,
+      details: {
+        actor,
+        backgroundScriptStatus,
+        location,
+        manifestURL,
+        persistentBackgroundScript,
+        uuid,
+        warnings: warnings || [],
+      },
+    };
+  });
+}
+
+module.exports = extensionComponentDataMiddleware;
diff --git a/devtools/client/aboutdebugging/src/middleware/moz.build b/devtools/client/aboutdebugging/src/middleware/moz.build
new file mode 100644
index 0000000000..f50150f569
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/middleware/moz.build
@@ -0,0 +1,13 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "debug-target-listener.js",
+    "error-logging.js",
+    "event-recording.js",
+    "extension-component-data.js",
+    "process-component-data.js",
+    "tab-component-data.js",
+    "worker-component-data.js",
+)
diff --git a/devtools/client/aboutdebugging/src/middleware/process-component-data.js b/devtools/client/aboutdebugging/src/middleware/process-component-data.js
new file mode 100644
index 0000000000..d5cdc6365b
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/middleware/process-component-data.js
@@ -0,0 +1,55 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  l10n,
+} = require("resource://devtools/client/aboutdebugging/src/modules/l10n.js");
+
+const {
+  DEBUG_TARGETS,
+  REQUEST_PROCESSES_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This middleware converts tabs object that get from DevToolsClient.listProcesses() to
+ * data which is used in DebugTargetItem.
+ */
+const processComponentDataMiddleware = store => next => action => {
+  switch (action.type) {
+    case REQUEST_PROCESSES_SUCCESS: {
+      const mainProcessComponentData = toMainProcessComponentData(
+        action.mainProcess
+      );
+      action.processes = [mainProcessComponentData];
+      break;
+    }
+  }
+
+  return next(action);
+};
+
+function toMainProcessComponentData(process) {
+  const type = DEBUG_TARGETS.PROCESS;
+  const icon = "chrome://devtools/skin/images/aboutdebugging-process-icon.svg";
+
+  // For now, we assume there is only one process and this is the main process
+  // So the name and title are for a remote (multiprocess) browser toolbox.
+  const name = l10n.getString("about-debugging-multiprocess-toolbox-name");
+  const description = l10n.getString(
+    "about-debugging-multiprocess-toolbox-description"
+  );
+
+  return {
+    name,
+    icon,
+    type,
+    details: {
+      description,
+    },
+  };
+}
+
+module.exports = processComponentDataMiddleware;
diff --git a/devtools/client/aboutdebugging/src/middleware/tab-component-data.js b/devtools/client/aboutdebugging/src/middleware/tab-component-data.js
new file mode 100644
index 0000000000..f468926f81
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/middleware/tab-component-data.js
@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  DEBUG_TARGETS,
+  REQUEST_TABS_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This middleware converts tabs object that get from DevToolsClient.listTabs() to data
+ * which is used in DebugTargetItem.
+ */
+const tabComponentDataMiddleware = store => next => action => {
+  switch (action.type) {
+    case REQUEST_TABS_SUCCESS: {
+      action.tabs = toComponentData(action.tabs);
+      break;
+    }
+  }
+
+  return next(action);
+};
+
+function toComponentData(tabs) {
+  return tabs.map(tab => {
+    const type = DEBUG_TARGETS.TAB;
+    const id = tab.browserId;
+    const icon = tab.favicon
+      ? `data:image/png;base64,${btoa(
+          String.fromCharCode.apply(String, tab.favicon)
+        )}`
+      : "chrome://devtools/skin/images/globe.svg";
+    const name = tab.title || tab.url;
+    const { url, isZombieTab } = tab;
+    return {
+      name,
+      icon,
+      id,
+      type,
+      details: {
+        isZombieTab,
+        url,
+      },
+    };
+  });
+}
+
+module.exports = tabComponentDataMiddleware;
diff --git a/devtools/client/aboutdebugging/src/middleware/worker-component-data.js b/devtools/client/aboutdebugging/src/middleware/worker-component-data.js
new file mode 100644
index 0000000000..178c99e322
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/middleware/worker-component-data.js
@@ -0,0 +1,82 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  DEBUG_TARGETS,
+  REQUEST_WORKERS_SUCCESS,
+  SERVICE_WORKER_FETCH_STATES,
+  SERVICE_WORKER_STATUSES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This middleware converts workers object that get from DevToolsClient.listAllWorkers()
+ * to data which is used in DebugTargetItem.
+ */
+const workerComponentDataMiddleware = store => next => action => {
+  switch (action.type) {
+    case REQUEST_WORKERS_SUCCESS: {
+      action.otherWorkers = toComponentData(action.otherWorkers);
+      action.serviceWorkers = toComponentData(action.serviceWorkers, true);
+      action.sharedWorkers = toComponentData(action.sharedWorkers);
+      break;
+    }
+  }
+
+  return next(action);
+};
+
+function getServiceWorkerStatus(worker) {
+  const isActive = worker.state === Ci.nsIServiceWorkerInfo.STATE_ACTIVATED;
+  const isRunning = !!worker.workerDescriptorFront;
+
+  if (isActive && isRunning) {
+    return SERVICE_WORKER_STATUSES.RUNNING;
+  } else if (isActive) {
+    return SERVICE_WORKER_STATUSES.STOPPED;
+  }
+
+  // We cannot get service worker registrations unless the registration is in
+  // ACTIVE state. Unable to know the actual state ("installing", "waiting"), we
+  // display a custom state "registering" for now. See Bug 1153292.
+  return SERVICE_WORKER_STATUSES.REGISTERING;
+}
+
+function toComponentData(workers, isServiceWorker) {
+  return workers.map(worker => {
+    // Here `worker` is the worker object created by RootFront.listAllWorkers
+    const type = DEBUG_TARGETS.WORKER;
+    const icon = "chrome://devtools/skin/images/debugging-workers.svg";
+    let { fetch } = worker;
+    const { id, name, registrationFront, scope, subscription } = worker;
+
+    let pushServiceEndpoint = null;
+    let status = null;
+
+    if (isServiceWorker) {
+      fetch = fetch
+        ? SERVICE_WORKER_FETCH_STATES.LISTENING
+        : SERVICE_WORKER_FETCH_STATES.NOT_LISTENING;
+      status = getServiceWorkerStatus(worker);
+      pushServiceEndpoint = subscription ? subscription.endpoint : null;
+    }
+
+    return {
+      details: {
+        fetch,
+        pushServiceEndpoint,
+        registrationFront,
+        scope,
+        status,
+      },
+      icon,
+      id,
+      name,
+      type,
+    };
+  });
+}
+
+module.exports = workerComponentDataMiddleware;
diff --git a/devtools/client/aboutdebugging/src/modules/client-wrapper.js b/devtools/client/aboutdebugging/src/modules/client-wrapper.js
new file mode 100644
index 0000000000..6d537b60a4
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/client-wrapper.js
@@ -0,0 +1,217 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  checkVersionCompatibility,
+} = require("resource://devtools/client/shared/remote-debugging/version-checker.js");
+
+const {
+  RUNTIME_PREFERENCE,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+const {
+  WorkersListener,
+} = require("resource://devtools/client/shared/workers-listener.js");
+const RootResourceCommand = require("resource://devtools/shared/commands/root-resource/root-resource-command.js");
+
+const PREF_TYPES = {
+  BOOL: "BOOL",
+};
+
+// Map of preference to preference type.
+const PREF_TO_TYPE = {
+  [RUNTIME_PREFERENCE.CHROME_DEBUG_ENABLED]: PREF_TYPES.BOOL,
+  [RUNTIME_PREFERENCE.CONNECTION_PROMPT]: PREF_TYPES.BOOL,
+  [RUNTIME_PREFERENCE.PERMANENT_PRIVATE_BROWSING]: PREF_TYPES.BOOL,
+  [RUNTIME_PREFERENCE.REMOTE_DEBUG_ENABLED]: PREF_TYPES.BOOL,
+  [RUNTIME_PREFERENCE.SERVICE_WORKERS_ENABLED]: PREF_TYPES.BOOL,
+};
+
+// Some events are fired by mainRoot rather than client.
+const MAIN_ROOT_EVENTS = ["addonListChanged", "tabListChanged"];
+
+/**
+ * The ClientWrapper class is used to isolate aboutdebugging from the DevTools client API
+ * The modules of about:debugging should never call DevTools client APIs directly.
+ */
+class ClientWrapper {
+  constructor(client) {
+    this.client = client;
+    this.workersListener = new WorkersListener(client.mainRoot);
+  }
+
+  once(evt, listener) {
+    if (MAIN_ROOT_EVENTS.includes(evt)) {
+      this.client.mainRoot.once(evt, listener);
+    } else {
+      this.client.once(evt, listener);
+    }
+  }
+
+  on(evt, listener) {
+    if (evt === "workersUpdated") {
+      this.workersListener.addListener(listener);
+    } else if (MAIN_ROOT_EVENTS.includes(evt)) {
+      this.client.mainRoot.on(evt, listener);
+    } else {
+      this.client.on(evt, listener);
+    }
+  }
+
+  off(evt, listener) {
+    if (evt === "workersUpdated") {
+      this.workersListener.removeListener(listener);
+    } else if (MAIN_ROOT_EVENTS.includes(evt)) {
+      this.client.mainRoot.off(evt, listener);
+    } else {
+      this.client.off(evt, listener);
+    }
+  }
+
+  async getFront(typeName) {
+    return this.client.mainRoot.getFront(typeName);
+  }
+
+  async getDeviceDescription() {
+    const deviceFront = await this.getFront("device");
+    const description = await deviceFront.getDescription();
+
+    // Only expose a specific set of properties.
+    return {
+      canDebugServiceWorkers: description.canDebugServiceWorkers,
+      channel: description.channel,
+      deviceName: description.deviceName,
+      name: description.brandName,
+      os: description.os,
+      version: description.version,
+    };
+  }
+
+  createRootResourceCommand() {
+    return new RootResourceCommand({ rootFront: this.client.mainRoot });
+  }
+
+  async checkVersionCompatibility() {
+    return checkVersionCompatibility(this.client);
+  }
+
+  async setPreference(prefName, value) {
+    const prefType = PREF_TO_TYPE[prefName];
+    const preferenceFront = await this.client.mainRoot.getFront("preference");
+    switch (prefType) {
+      case PREF_TYPES.BOOL:
+        return preferenceFront.setBoolPref(prefName, value);
+      default:
+        throw new Error("Unsupported preference" + prefName);
+    }
+  }
+
+  async getPreference(prefName, defaultValue) {
+    if (typeof defaultValue === "undefined") {
+      throw new Error(
+        "Default value is mandatory for getPreference, the actor will " +
+          "throw if the preference is not set on the target runtime"
+      );
+    }
+
+    const prefType = PREF_TO_TYPE[prefName];
+    const preferenceFront = await this.client.mainRoot.getFront("preference");
+    switch (prefType) {
+      case PREF_TYPES.BOOL:
+        // TODO: Add server-side trait and methods to pass a default value to getBoolPref.
+        // See Bug 1522588.
+        let prefValue;
+        try {
+          prefValue = await preferenceFront.getBoolPref(prefName);
+        } catch (e) {
+          prefValue = defaultValue;
+        }
+        return prefValue;
+      default:
+        throw new Error("Unsupported preference:" + prefName);
+    }
+  }
+
+  async listTabs() {
+    return this.client.mainRoot.listTabs();
+  }
+
+  async listAddons(options) {
+    return this.client.mainRoot.listAddons(options);
+  }
+
+  async getAddon({ id }) {
+    return this.client.mainRoot.getAddon({ id });
+  }
+
+  async uninstallAddon({ id }) {
+    const addonsFront = await this.getFront("addons");
+    return addonsFront.uninstallAddon(id);
+  }
+
+  async getMainProcess() {
+    return this.client.mainRoot.getMainProcess();
+  }
+
+  async getServiceWorkerFront({ id }) {
+    return this.client.mainRoot.getWorker(id);
+  }
+
+  async listWorkers() {
+    const { other, service, shared } =
+      await this.client.mainRoot.listAllWorkers();
+
+    return {
+      otherWorkers: other,
+      serviceWorkers: service,
+      sharedWorkers: shared,
+    };
+  }
+
+  async close() {
+    return this.client.close();
+  }
+
+  isClosed() {
+    return this.client._transportClosed;
+  }
+
+  // This method will be mocked to return a dummy URL during mochitests
+  getPerformancePanelUrl() {
+    return "chrome://devtools/content/performance-new/panel/index.xhtml";
+  }
+
+  /**
+   * @param {Window} win - The window of the dialog window.
+   * @param {Function} openAboutProfiling
+   */
+  async loadPerformanceProfiler(win, openAboutProfiling) {
+    const perfFront = await this.getFront("perf");
+    const { traits } = this.client;
+    await win.gInit(perfFront, traits, "devtools-remote", openAboutProfiling);
+  }
+
+  /**
+   * @param {Window} win - The window of the dialog window.
+   * @param {Function} openRemoteDevTools
+   */
+  async loadAboutProfiling(win, openRemoteDevTools) {
+    const perfFront = await this.getFront("perf");
+    const isSupportedPlatform = await perfFront.isSupportedPlatform();
+    const supportedFeatures = await perfFront.getSupportedFeatures();
+    await win.gInit(
+      "aboutprofiling-remote",
+      isSupportedPlatform,
+      supportedFeatures,
+      openRemoteDevTools
+    );
+  }
+
+  get traits() {
+    return { ...this.client.mainRoot.traits };
+  }
+}
+
+exports.ClientWrapper = ClientWrapper;
diff --git a/devtools/client/aboutdebugging/src/modules/debug-target-collapsibilities.js b/devtools/client/aboutdebugging/src/modules/debug-target-collapsibilities.js
new file mode 100644
index 0000000000..efba47e03a
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/debug-target-collapsibilities.js
@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const PREF_PREFIX = "devtools.aboutdebugging.collapsibilities.";
+const {
+  DEBUG_TARGET_PANE,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+/**
+ * This module provides a collection of helper methods to read and update the debug
+ * target pane's collapsibilities.
+ */
+
+/**
+ * @return {Object}
+ *         {
+ *           key: constants.DEBUG_TARGET_PANE
+ *           value: true - collapsed
+ *                  false - expanded
+ *         }
+ */
+function getDebugTargetCollapsibilities() {
+  const map = new Map();
+
+  for (const key of Object.values(DEBUG_TARGET_PANE)) {
+    const pref = Services.prefs.getBoolPref(PREF_PREFIX + key, false);
+    map.set(key, pref);
+  }
+
+  return map;
+}
+exports.getDebugTargetCollapsibilities = getDebugTargetCollapsibilities;
+
+/**
+ * @param collapsibilities - Same format to getDebugTargetCollapsibilities.
+ */
+function setDebugTargetCollapsibilities(collapsibilities) {
+  for (const key of Object.values(DEBUG_TARGET_PANE)) {
+    const isCollapsed = collapsibilities.get(key);
+    Services.prefs.setBoolPref(PREF_PREFIX + key, isCollapsed);
+  }
+}
+exports.setDebugTargetCollapsibilities = setDebugTargetCollapsibilities;
diff --git a/devtools/client/aboutdebugging/src/modules/debug-target-support.js b/devtools/client/aboutdebugging/src/modules/debug-target-support.js
new file mode 100644
index 0000000000..2b8d4afa5b
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/debug-target-support.js
@@ -0,0 +1,98 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  DEBUG_TARGET_PANE,
+  PREFERENCES,
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+// Process target debugging is disabled by default.
+function isProcessDebuggingSupported() {
+  return Services.prefs.getBoolPref(
+    PREFERENCES.PROCESS_DEBUGGING_ENABLED,
+    false
+  );
+}
+
+// Local tab debugging is disabled by default.
+function isLocalTabDebuggingSupported() {
+  return Services.prefs.getBoolPref(
+    PREFERENCES.LOCAL_TAB_DEBUGGING_ENABLED,
+    false
+  );
+}
+
+// Local process debugging is disabled by default.
+// This preference has no default value in
+// devtools/client/preferences/devtools-client.js
+// because it is only intended for tests.
+function isLocalProcessDebuggingSupported() {
+  return Services.prefs.getBoolPref(
+    "devtools.aboutdebugging.test-local-process-debugging",
+    false
+  );
+}
+
+// Installing extensions can be disabled in enterprise policy.
+// Note: Temporary Extensions are only supported when debugging This Firefox, so checking
+// the local preference is acceptable here. If we enable Temporary extensions for remote
+// runtimes, we should retrieve the preference from the target runtime instead.
+function isTemporaryExtensionSupported() {
+  return Services.prefs.getBoolPref(PREFERENCES.XPINSTALL_ENABLED, true);
+}
+
+const ALL_DEBUG_TARGET_PANES = [
+  DEBUG_TARGET_PANE.INSTALLED_EXTENSION,
+  ...(isProcessDebuggingSupported() ? [DEBUG_TARGET_PANE.PROCESSES] : []),
+  DEBUG_TARGET_PANE.OTHER_WORKER,
+  DEBUG_TARGET_PANE.SERVICE_WORKER,
+  DEBUG_TARGET_PANE.SHARED_WORKER,
+  DEBUG_TARGET_PANE.TAB,
+  ...(isTemporaryExtensionSupported()
+    ? [DEBUG_TARGET_PANE.TEMPORARY_EXTENSION]
+    : []),
+];
+
+// All debug target panes (to filter out if any of the panels should be excluded).
+const REMOTE_DEBUG_TARGET_PANES = [...ALL_DEBUG_TARGET_PANES];
+
+const THIS_FIREFOX_DEBUG_TARGET_PANES = ALL_DEBUG_TARGET_PANES
+  // Main process debugging is not available for This Firefox.
+  // At the moment only the main process is listed under processes, so remove the category
+  // for this runtime.
+  .filter(
+    p => p !== DEBUG_TARGET_PANE.PROCESSES || isLocalProcessDebuggingSupported()
+  )
+  // Showing tab targets for This Firefox is behind a preference.
+  .filter(p => p !== DEBUG_TARGET_PANE.TAB || isLocalTabDebuggingSupported());
+
+const SUPPORTED_TARGET_PANE_BY_RUNTIME = {
+  [RUNTIMES.THIS_FIREFOX]: THIS_FIREFOX_DEBUG_TARGET_PANES,
+  [RUNTIMES.USB]: REMOTE_DEBUG_TARGET_PANES,
+  [RUNTIMES.NETWORK]: REMOTE_DEBUG_TARGET_PANES,
+};
+
+/**
+ * A debug target pane is more specialized than a debug target. For instance EXTENSION is
+ * a DEBUG_TARGET but INSTALLED_EXTENSION and TEMPORARY_EXTENSION are DEBUG_TARGET_PANES.
+ */
+function isSupportedDebugTargetPane(runtimeType, debugTargetPaneKey) {
+  return SUPPORTED_TARGET_PANE_BY_RUNTIME[runtimeType].includes(
+    debugTargetPaneKey
+  );
+}
+exports.isSupportedDebugTargetPane = isSupportedDebugTargetPane;
+
+/**
+ * Check if the given runtimeType supports temporary extension installation
+ * from about:debugging (currently disallowed on non-local runtimes).
+ */
+function supportsTemporaryExtensionInstaller(runtimeType) {
+  return runtimeType === RUNTIMES.THIS_FIREFOX;
+}
+exports.supportsTemporaryExtensionInstaller =
+  supportsTemporaryExtensionInstaller;
diff --git a/devtools/client/aboutdebugging/src/modules/extensions-helper.js b/devtools/client/aboutdebugging/src/modules/extensions-helper.js
new file mode 100644
index 0000000000..ec0d7c2661
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/extensions-helper.js
@@ -0,0 +1,92 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
+});
+
+const {
+  PREFERENCES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+exports.parseFileUri = function (url) {
+  // Strip a leading slash from Windows drive letter URIs.
+  // file:///home/foo ~> /home/foo
+  // file:///C:/foo ~> C:/foo
+  const windowsRegex = /^file:\/\/\/([a-zA-Z]:\/.*)/;
+  if (windowsRegex.test(url)) {
+    return windowsRegex.exec(url)[1];
+  }
+  return url.slice("file://".length);
+};
+
+exports.getExtensionUuid = function (extension) {
+  const { manifestURL } = extension;
+  // Strip off the protocol and rest, leaving us with just the UUID.
+  return manifestURL ? /moz-extension:\/\/([^/]*)/.exec(manifestURL)[1] : null;
+};
+
+/**
+ * Open a file picker to allow the user to locate a temporary extension. A temporary
+ * extension can either be:
+ * - a folder
+ * - a .xpi file
+ * - a .zip file
+ *
+ * @param  {Window} win
+ *         The window object where the filepicker should be opened.
+ *         Note: We cannot use the global window object here because it is undefined if
+ *         this module is loaded from a file outside of devtools/client/aboutdebugging/.
+ *         See browser-loader.js `uri.startsWith(baseURI)` for more details.
+ * @param  {String} message
+ *         The help message that should be displayed to the user in the filepicker.
+ * @return {Promise} returns a promise that resolves a File object corresponding to the
+ *         file selected by the user.
+ */
+exports.openTemporaryExtension = function (win, message) {
+  return new Promise(resolve => {
+    const fp = Cc["@mozilla.org/filepicker;1"].createInstance(Ci.nsIFilePicker);
+    fp.init(win, message, Ci.nsIFilePicker.modeOpen);
+
+    // Try to set the last directory used as "displayDirectory".
+    try {
+      const lastDirPath = Services.prefs.getCharPref(
+        PREFERENCES.TEMPORARY_EXTENSION_PATH,
+        ""
+      );
+      const lastDir = new lazy.FileUtils.File(lastDirPath);
+      fp.displayDirectory = lastDir;
+    } catch (e) {
+      // Empty or invalid value, nothing to handle.
+    }
+
+    fp.open(res => {
+      if (res == Ci.nsIFilePicker.returnCancel || !fp.file) {
+        return;
+      }
+      let file = fp.file;
+      // AddonManager.installTemporaryAddon accepts either
+      // addon directory or final xpi file.
+      if (
+        !file.isDirectory() &&
+        !file.leafName.endsWith(".xpi") &&
+        !file.leafName.endsWith(".zip")
+      ) {
+        file = file.parent;
+      }
+
+      // We are about to resolve, store the path to the file for the next call.
+      Services.prefs.setCharPref(
+        PREFERENCES.TEMPORARY_EXTENSION_PATH,
+        file.path
+      );
+
+      resolve(file);
+    });
+  });
+};
diff --git a/devtools/client/aboutdebugging/src/modules/l10n.js b/devtools/client/aboutdebugging/src/modules/l10n.js
new file mode 100644
index 0000000000..88c7ae8bb1
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/l10n.js
@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  FluentL10n,
+} = require("resource://devtools/client/shared/fluent-l10n/fluent-l10n.js");
+
+// exports a singleton, which will be used across all aboutdebugging modules
+exports.l10n = new FluentL10n();
diff --git a/devtools/client/aboutdebugging/src/modules/moz.build b/devtools/client/aboutdebugging/src/modules/moz.build
new file mode 100644
index 0000000000..909e181714
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/moz.build
@@ -0,0 +1,16 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "client-wrapper.js",
+    "debug-target-collapsibilities.js",
+    "debug-target-support.js",
+    "extensions-helper.js",
+    "l10n.js",
+    "network-locations.js",
+    "runtime-client-factory.js",
+    "runtime-default-preferences.js",
+    "runtimes-state-helper.js",
+    "usb-runtimes.js",
+)
diff --git a/devtools/client/aboutdebugging/src/modules/network-locations.js b/devtools/client/aboutdebugging/src/modules/network-locations.js
new file mode 100644
index 0000000000..cbae436df7
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/network-locations.js
@@ -0,0 +1,69 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const NETWORK_LOCATIONS_PREF = "devtools.aboutdebugging.network-locations";
+
+/**
+ * This module provides a collection of helper methods to read and update network
+ * locations monitored by about-debugging.
+ */
+
+function addNetworkLocationsObserver(listener) {
+  Services.prefs.addObserver(NETWORK_LOCATIONS_PREF, listener);
+}
+exports.addNetworkLocationsObserver = addNetworkLocationsObserver;
+
+function removeNetworkLocationsObserver(listener) {
+  Services.prefs.removeObserver(NETWORK_LOCATIONS_PREF, listener);
+}
+exports.removeNetworkLocationsObserver = removeNetworkLocationsObserver;
+
+/**
+ * Read the current preference value for aboutdebugging network locations.
+ * Will throw if the value cannot be parsed or is not an array.
+ */
+function _parsePreferenceAsArray() {
+  const pref = Services.prefs.getStringPref(NETWORK_LOCATIONS_PREF, "[]");
+  const parsedValue = JSON.parse(pref);
+  if (!Array.isArray(parsedValue)) {
+    throw new Error("Expected array value in " + NETWORK_LOCATIONS_PREF);
+  }
+  return parsedValue;
+}
+
+function getNetworkLocations() {
+  try {
+    return _parsePreferenceAsArray();
+  } catch (e) {
+    Services.prefs.clearUserPref(NETWORK_LOCATIONS_PREF);
+    return [];
+  }
+}
+exports.getNetworkLocations = getNetworkLocations;
+
+function addNetworkLocation(location) {
+  const locations = getNetworkLocations();
+  const locationsSet = new Set(locations);
+  locationsSet.add(location);
+
+  Services.prefs.setStringPref(
+    NETWORK_LOCATIONS_PREF,
+    JSON.stringify([...locationsSet])
+  );
+}
+exports.addNetworkLocation = addNetworkLocation;
+
+function removeNetworkLocation(location) {
+  const locations = getNetworkLocations();
+  const locationsSet = new Set(locations);
+  locationsSet.delete(location);
+
+  Services.prefs.setStringPref(
+    NETWORK_LOCATIONS_PREF,
+    JSON.stringify([...locationsSet])
+  );
+}
+exports.removeNetworkLocation = removeNetworkLocation;
diff --git a/devtools/client/aboutdebugging/src/modules/runtime-client-factory.js b/devtools/client/aboutdebugging/src/modules/runtime-client-factory.js
new file mode 100644
index 0000000000..e553416c18
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/runtime-client-factory.js
@@ -0,0 +1,68 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  prepareTCPConnection,
+} = require("resource://devtools/client/shared/remote-debugging/adb/commands/index.js");
+const {
+  DevToolsClient,
+} = require("resource://devtools/client/devtools-client.js");
+const {
+  DevToolsServer,
+} = require("resource://devtools/server/devtools-server.js");
+const {
+  ClientWrapper,
+} = require("resource://devtools/client/aboutdebugging/src/modules/client-wrapper.js");
+const {
+  remoteClientManager,
+} = require("resource://devtools/client/shared/remote-debugging/remote-client-manager.js");
+
+const {
+  RUNTIMES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+async function createLocalClient() {
+  DevToolsServer.init();
+  DevToolsServer.registerAllActors();
+  DevToolsServer.allowChromeProcess = true;
+
+  const client = new DevToolsClient(DevToolsServer.connectPipe());
+  await client.connect();
+  return new ClientWrapper(client);
+}
+
+async function createNetworkClient(host, port) {
+  const transport = await DevToolsClient.socketConnect({ host, port });
+  const client = new DevToolsClient(transport);
+  await client.connect();
+  return new ClientWrapper(client);
+}
+
+async function createUSBClient(deviceId, socketPath) {
+  const port = await prepareTCPConnection(deviceId, socketPath);
+  return createNetworkClient("localhost", port);
+}
+
+async function createClientForRuntime(runtime) {
+  const { extra, id, type } = runtime;
+
+  if (type === RUNTIMES.THIS_FIREFOX) {
+    return createLocalClient();
+  } else if (remoteClientManager.hasClient(id, type)) {
+    const client = remoteClientManager.getClient(id, type);
+    return new ClientWrapper(client);
+  } else if (type === RUNTIMES.NETWORK) {
+    const { host, port } = extra.connectionParameters;
+    return createNetworkClient(host, port);
+  } else if (type === RUNTIMES.USB) {
+    const { deviceId, socketPath } = extra.connectionParameters;
+    return createUSBClient(deviceId, socketPath);
+  }
+
+  return null;
+}
+
+exports.createClientForRuntime = createClientForRuntime;
diff --git a/devtools/client/aboutdebugging/src/modules/runtime-default-preferences.js b/devtools/client/aboutdebugging/src/modules/runtime-default-preferences.js
new file mode 100644
index 0000000000..02c06334f7
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/runtime-default-preferences.js
@@ -0,0 +1,101 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * This module provides a workaround for remote debugging when a preference is
+ * defined in the firefox preference file (browser/app/profile/firefox.js) but
+ * still read from the server, without any default value.
+ *
+ * This causes the server to crash and can't easily be recovered.
+ *
+ * While we work on better linting to prevent such issues (Bug 1660182), this
+ * module will be able to set default values for all missing preferences.
+ */
+
+const PREFERENCE_TYPES = {
+  BOOL: "BOOL",
+  CHAR: "CHAR",
+  INT: "INT",
+};
+exports.PREFERENCE_TYPES = PREFERENCE_TYPES;
+
+/**
+ * Expected properties for the preference descriptors:
+ * - prefName {String}: the name of the preference.
+ * - defaultValue {String|Bool|Number}: the value to set if the preference is
+ *   missing.
+ * - trait {String}: the name of the trait corresponding to this pref on the
+ *   PreferenceFront.
+ * - type {String}: the preference type (either BOOL, CHAR or INT).
+ */
+const DEFAULT_PREFERENCES = [];
+exports.DEFAULT_PREFERENCES = DEFAULT_PREFERENCES;
+
+const METHODS = {
+  [PREFERENCE_TYPES.BOOL]: {
+    setPref: "setBoolPref",
+    getPref: "getBoolPref",
+  },
+  [PREFERENCE_TYPES.CHAR]: {
+    setPref: "setCharPref",
+    getPref: "getCharPref",
+  },
+  [PREFERENCE_TYPES.INT]: {
+    setPref: "setIntPref",
+    getPref: "getIntPref",
+  },
+};
+
+/**
+ * Set default values for all the provided preferences on the runtime
+ * corresponding to the provided clientWrapper, if needed.
+ *
+ * Note: prefDescriptors will most likely be DEFAULT_PREFERENCES when
+ * used in production code, but can be parameterized for tests.
+ *
+ * @param {ClientWrapper} clientWrapper
+ * @param {Array} prefDescriptors
+ *        Array of preference descriptors, see DEFAULT_PREFERENCES.
+ */
+async function setDefaultPreferencesIfNeeded(clientWrapper, prefDescriptors) {
+  if (!prefDescriptors || prefDescriptors.length === 0) {
+    return;
+  }
+
+  const preferenceFront = await clientWrapper.getFront("preference");
+  const preferenceTraits = await preferenceFront.getTraits();
+
+  // Note: using Promise.all here fails because the request/responses get mixed.
+  for (const prefDescriptor of prefDescriptors) {
+    // If the fix for this preference is already on this server, skip it.
+    if (preferenceTraits[prefDescriptor.trait]) {
+      continue;
+    }
+
+    await setDefaultPreference(preferenceFront, prefDescriptor);
+  }
+}
+exports.setDefaultPreferencesIfNeeded = setDefaultPreferencesIfNeeded;
+
+async function setDefaultPreference(preferenceFront, prefDescriptor) {
+  const { prefName, type, defaultValue } = prefDescriptor;
+
+  if (!Object.values(PREFERENCE_TYPES).includes(type)) {
+    throw new Error(`Unsupported type for setDefaultPreference "${type}"`);
+  }
+
+  const prefMethods = METHODS[type];
+  try {
+    // Try to read the preference only to check if the call is successful.
+    // If not, this means the preference is missing and should be initialized.
+    await preferenceFront[prefMethods.getPref](prefName);
+  } catch (e) {
+    console.warn(
+      `Preference "${prefName}"" is not set on the remote runtime. Setting default value.`
+    );
+    await preferenceFront[prefMethods.setPref](prefName, defaultValue);
+  }
+}
diff --git a/devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js b/devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js
new file mode 100644
index 0000000000..1864ef8341
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js
@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+function getCurrentRuntime(runtimesState) {
+  const selectedRuntimeId = runtimesState.selectedRuntimeId;
+  return findRuntimeById(selectedRuntimeId, runtimesState);
+}
+exports.getCurrentRuntime = getCurrentRuntime;
+
+function getCurrentClient(runtimesState) {
+  const runtimeDetails = getCurrentRuntimeDetails(runtimesState);
+  return runtimeDetails ? runtimeDetails.clientWrapper : null;
+}
+exports.getCurrentClient = getCurrentClient;
+
+function findRuntimeById(id, runtimesState) {
+  return getAllRuntimes(runtimesState).find(r => r.id === id);
+}
+exports.findRuntimeById = findRuntimeById;
+
+function getAllRuntimes(runtimesState) {
+  return [
+    ...runtimesState.networkRuntimes,
+    ...runtimesState.thisFirefoxRuntimes,
+    ...runtimesState.usbRuntimes,
+  ];
+}
+exports.getAllRuntimes = getAllRuntimes;
+
+function getCurrentRuntimeDetails(runtimesState) {
+  const runtime = getCurrentRuntime(runtimesState);
+  return runtime ? runtime.runtimeDetails : null;
+}
+exports.getCurrentRuntimeDetails = getCurrentRuntimeDetails;
diff --git a/devtools/client/aboutdebugging/src/modules/usb-runtimes.js b/devtools/client/aboutdebugging/src/modules/usb-runtimes.js
new file mode 100644
index 0000000000..887dc6788e
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/modules/usb-runtimes.js
@@ -0,0 +1,122 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+loader.lazyRequireGetter(
+  this,
+  "adb",
+  "resource://devtools/client/shared/remote-debugging/adb/adb.js",
+  true
+);
+
+/**
+ * Used to represent a regular runtime returned by ADB.
+ */
+class UsbRuntime {
+  constructor(adbRuntime) {
+    this.id = adbRuntime.id;
+    this.deviceId = adbRuntime.deviceId;
+    this.deviceName = adbRuntime.deviceName;
+    this.shortName = adbRuntime.shortName;
+    this.socketPath = adbRuntime.socketPath;
+    this.isFenix = adbRuntime.isFenix;
+    this.isUnavailable = false;
+    this.isUnplugged = false;
+    this.versionName = adbRuntime.versionName;
+  }
+}
+
+/**
+ * Used when a device was detected, meaning USB debugging is enabled on the device, but no
+ * runtime/browser is available for connection.
+ */
+class UnavailableUsbRuntime {
+  constructor(adbDevice) {
+    this.id = adbDevice.id + "|unavailable";
+    this.deviceId = adbDevice.id;
+    this.deviceName = adbDevice.name;
+    this.shortName = "Unavailable runtime";
+    this.socketPath = null;
+    this.isFenix = false;
+    this.isUnavailable = true;
+    this.isUnplugged = false;
+    this.versionName = null;
+  }
+}
+
+/**
+ * Used to represent USB devices that were previously connected but are now missing
+ * (presumably after being unplugged/disconnected from the computer).
+ */
+class UnpluggedUsbRuntime {
+  constructor(deviceId, deviceName) {
+    this.id = deviceId + "|unplugged";
+    this.deviceId = deviceId;
+    this.deviceName = deviceName;
+    this.shortName = "Unplugged runtime";
+    this.socketPath = null;
+    this.isFenix = false;
+    this.isUnavailable = true;
+    this.isUnplugged = true;
+    this.versionName = null;
+  }
+}
+
+/**
+ * Map used to keep track of discovered usb devices. Will be used to create the unplugged
+ * usb runtimes.
+ */
+const devices = new Map();
+
+/**
+ * This module provides a collection of helper methods to detect USB runtimes whom Firefox
+ * is running on.
+ */
+function addUSBRuntimesObserver(listener) {
+  adb.registerListener(listener);
+}
+exports.addUSBRuntimesObserver = addUSBRuntimesObserver;
+
+async function getUSBRuntimes() {
+  // Get the available runtimes
+  const runtimes = adb.getRuntimes().map(r => new UsbRuntime(r));
+
+  // Get devices found by ADB, but without any available runtime.
+  const runtimeDevices = runtimes.map(r => r.deviceId);
+  const unavailableRuntimes = adb
+    .getDevices()
+    .filter(d => !runtimeDevices.includes(d.id))
+    .map(d => new UnavailableUsbRuntime(d));
+
+  // Add all devices to the map detected devices.
+  const allRuntimes = runtimes.concat(unavailableRuntimes);
+  for (const runtime of allRuntimes) {
+    devices.set(runtime.deviceId, runtime.deviceName);
+  }
+
+  // Get devices previously found by ADB but no longer available.
+  const currentDevices = allRuntimes.map(r => r.deviceId);
+  const detectedDevices = [...devices.keys()];
+  const unpluggedDevices = detectedDevices.filter(
+    id => !currentDevices.includes(id)
+  );
+  const unpluggedRuntimes = unpluggedDevices.map(deviceId => {
+    const deviceName = devices.get(deviceId);
+    return new UnpluggedUsbRuntime(deviceId, deviceName);
+  });
+
+  return allRuntimes.concat(unpluggedRuntimes);
+}
+exports.getUSBRuntimes = getUSBRuntimes;
+
+function removeUSBRuntimesObserver(listener) {
+  adb.unregisterListener(listener);
+}
+exports.removeUSBRuntimesObserver = removeUSBRuntimesObserver;
+
+function refreshUSBRuntimes() {
+  return adb.updateRuntimes();
+}
+exports.refreshUSBRuntimes = refreshUSBRuntimes;
diff --git a/devtools/client/aboutdebugging/src/moz.build b/devtools/client/aboutdebugging/src/moz.build
new file mode 100644
index 0000000000..58e6f92857
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/moz.build
@@ -0,0 +1,17 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += [
+    "actions",
+    "components",
+    "middleware",
+    "modules",
+    "reducers",
+    "types",
+]
+
+DevToolsModules(
+    "constants.js",
+    "create-store.js",
+)
diff --git a/devtools/client/aboutdebugging/src/reducers/debug-targets-state.js b/devtools/client/aboutdebugging/src/reducers/debug-targets-state.js
new file mode 100644
index 0000000000..8ee0473e3c
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/reducers/debug-targets-state.js
@@ -0,0 +1,155 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  EXTENSION_BGSCRIPT_STATUS_UPDATED,
+  REQUEST_EXTENSIONS_SUCCESS,
+  REQUEST_PROCESSES_SUCCESS,
+  REQUEST_TABS_SUCCESS,
+  REQUEST_WORKERS_SUCCESS,
+  TEMPORARY_EXTENSION_RELOAD_FAILURE,
+  TEMPORARY_EXTENSION_RELOAD_START,
+  TERMINATE_EXTENSION_BGSCRIPT_FAILURE,
+  TERMINATE_EXTENSION_BGSCRIPT_START,
+  UNWATCH_RUNTIME_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+function DebugTargetsState() {
+  return {
+    installedExtensions: [],
+    otherWorkers: [],
+    processes: [],
+    serviceWorkers: [],
+    sharedWorkers: [],
+    tabs: [],
+    temporaryExtensions: [],
+  };
+}
+
+function updateExtensionDetails(extensions, id, updatedDetails) {
+  // extensions is meant to be either state.installExtensions or state.temporaryExtensions.
+  return extensions.map(extension => {
+    if (extension.id === id) {
+      extension = Object.assign({}, extension);
+
+      extension.details = Object.assign({}, extension.details, updatedDetails);
+    }
+    return extension;
+  });
+}
+
+function updateTemporaryExtension(state, id, updatedDetails) {
+  return updateExtensionDetails(state.temporaryExtensions, id, updatedDetails);
+}
+
+function updateInstalledExtension(state, id, updatedDetails) {
+  return updateExtensionDetails(state.installedExtensions, id, updatedDetails);
+}
+
+function updateExtension(state, id, updatedDetails) {
+  return {
+    installedExtensions: updateInstalledExtension(state, id, updatedDetails),
+    temporaryExtensions: updateTemporaryExtension(state, id, updatedDetails),
+  };
+}
+
+function debugTargetsReducer(state = DebugTargetsState(), action) {
+  switch (action.type) {
+    case UNWATCH_RUNTIME_SUCCESS: {
+      return DebugTargetsState();
+    }
+    case REQUEST_EXTENSIONS_SUCCESS: {
+      const { installedExtensions, temporaryExtensions } = action;
+      return Object.assign({}, state, {
+        installedExtensions,
+        temporaryExtensions,
+      });
+    }
+    case REQUEST_PROCESSES_SUCCESS: {
+      const { processes } = action;
+      return Object.assign({}, state, { processes });
+    }
+    case REQUEST_TABS_SUCCESS: {
+      const { tabs } = action;
+      return Object.assign({}, state, { tabs });
+    }
+    case REQUEST_WORKERS_SUCCESS: {
+      const { otherWorkers, serviceWorkers, sharedWorkers } = action;
+      return Object.assign({}, state, {
+        otherWorkers,
+        serviceWorkers,
+        sharedWorkers,
+      });
+    }
+    case TEMPORARY_EXTENSION_RELOAD_FAILURE: {
+      const { id, error } = action;
+      const temporaryExtensions = updateTemporaryExtension(state, id, {
+        reloadError: error.message,
+      });
+      return Object.assign({}, state, { temporaryExtensions });
+    }
+    case TEMPORARY_EXTENSION_RELOAD_START: {
+      const { id } = action;
+      const temporaryExtensions = updateTemporaryExtension(state, id, {
+        reloadError: null,
+      });
+      return Object.assign({}, state, { temporaryExtensions });
+    }
+    case TERMINATE_EXTENSION_BGSCRIPT_START: {
+      const { id } = action;
+      const { installedExtensions, temporaryExtensions } = updateExtension(
+        state,
+        id,
+        {
+          // Clear the last error if one was still set.
+          lastTerminateBackgroundScriptError: null,
+        }
+      );
+      return Object.assign({}, state, {
+        installedExtensions,
+        temporaryExtensions,
+      });
+    }
+    case TERMINATE_EXTENSION_BGSCRIPT_FAILURE: {
+      const { id, error } = action;
+      const { installedExtensions, temporaryExtensions } = updateExtension(
+        state,
+        id,
+        {
+          lastTerminateBackgroundScriptError: error.message,
+        }
+      );
+      return Object.assign({}, state, {
+        installedExtensions,
+        temporaryExtensions,
+      });
+    }
+    case EXTENSION_BGSCRIPT_STATUS_UPDATED: {
+      const { id, backgroundScriptStatus } = action;
+      const { installedExtensions, temporaryExtensions } = updateExtension(
+        state,
+        id,
+        {
+          backgroundScriptStatus,
+          // Clear the last error if one was still set.
+          lastTerminateBackgroundScriptError: null,
+        }
+      );
+      return Object.assign({}, state, {
+        installedExtensions,
+        temporaryExtensions,
+      });
+    }
+
+    default:
+      return state;
+  }
+}
+
+module.exports = {
+  DebugTargetsState,
+  debugTargetsReducer,
+};
diff --git a/devtools/client/aboutdebugging/src/reducers/index.js b/devtools/client/aboutdebugging/src/reducers/index.js
new file mode 100644
index 0000000000..8f104a4ff7
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/reducers/index.js
@@ -0,0 +1,24 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  combineReducers,
+} = require("resource://devtools/client/shared/vendor/redux.js");
+const {
+  debugTargetsReducer,
+} = require("resource://devtools/client/aboutdebugging/src/reducers/debug-targets-state.js");
+const {
+  runtimesReducer,
+} = require("resource://devtools/client/aboutdebugging/src/reducers/runtimes-state.js");
+const {
+  uiReducer,
+} = require("resource://devtools/client/aboutdebugging/src/reducers/ui-state.js");
+
+module.exports = combineReducers({
+  debugTargets: debugTargetsReducer,
+  runtimes: runtimesReducer,
+  ui: uiReducer,
+});
diff --git a/devtools/client/aboutdebugging/src/reducers/moz.build b/devtools/client/aboutdebugging/src/reducers/moz.build
new file mode 100644
index 0000000000..24d3382f5b
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/reducers/moz.build
@@ -0,0 +1,10 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "debug-targets-state.js",
+    "index.js",
+    "runtimes-state.js",
+    "ui-state.js",
+)
diff --git a/devtools/client/aboutdebugging/src/reducers/runtimes-state.js b/devtools/client/aboutdebugging/src/reducers/runtimes-state.js
new file mode 100644
index 0000000000..5acf35390a
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/reducers/runtimes-state.js
@@ -0,0 +1,178 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  CONNECT_RUNTIME_CANCEL,
+  CONNECT_RUNTIME_FAILURE,
+  CONNECT_RUNTIME_NOT_RESPONDING,
+  CONNECT_RUNTIME_START,
+  CONNECT_RUNTIME_SUCCESS,
+  DISCONNECT_RUNTIME_SUCCESS,
+  RUNTIMES,
+  UPDATE_CONNECTION_PROMPT_SETTING_SUCCESS,
+  REMOTE_RUNTIMES_UPDATED,
+  SELECTED_RUNTIME_ID_UPDATED,
+  THIS_FIREFOX_RUNTIME_CREATED,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const {
+  findRuntimeById,
+} = require("resource://devtools/client/aboutdebugging/src/modules/runtimes-state-helper.js");
+
+const {
+  remoteClientManager,
+} = require("resource://devtools/client/shared/remote-debugging/remote-client-manager.js");
+
+// Map between known runtime types and nodes in the runtimes state.
+const TYPE_TO_RUNTIMES_KEY = {
+  [RUNTIMES.THIS_FIREFOX]: "thisFirefoxRuntimes",
+  [RUNTIMES.NETWORK]: "networkRuntimes",
+  [RUNTIMES.USB]: "usbRuntimes",
+};
+
+function RuntimesState() {
+  return {
+    networkRuntimes: [],
+    selectedRuntimeId: null,
+    // "This Firefox" runtimes is an array for consistency, but it should only contain one
+    // runtime. This runtime will be added after initializing the application via
+    // THIS_FIREFOX_RUNTIME_CREATED.
+    thisFirefoxRuntimes: [],
+    usbRuntimes: [],
+  };
+}
+
+/**
+ * Update the runtime matching the provided runtimeId with the content of updatedRuntime,
+ * and return the new state.
+ *
+ * @param  {String} runtimeId
+ *         The id of the runtime to update
+ * @param  {Object} updatedRuntime
+ *         Object used to update the runtime matching the idea using Object.assign.
+ * @param  {Object} state
+ *         Current runtimes state.
+ * @return {Object} The updated state
+ */
+function _updateRuntimeById(runtimeId, updatedRuntime, state) {
+  // Find the array of runtimes that contains the updated runtime.
+  const runtime = findRuntimeById(runtimeId, state);
+  const key = TYPE_TO_RUNTIMES_KEY[runtime.type];
+  const runtimesToUpdate = state[key];
+
+  // Update the runtime with the provided updatedRuntime.
+  const updatedRuntimes = runtimesToUpdate.map(r => {
+    if (r.id === runtimeId) {
+      return Object.assign({}, r, updatedRuntime);
+    }
+    return r;
+  });
+  return Object.assign({}, state, { [key]: updatedRuntimes });
+}
+
+function runtimesReducer(state = RuntimesState(), action) {
+  switch (action.type) {
+    case CONNECT_RUNTIME_START: {
+      const { id } = action;
+      const updatedState = {
+        isConnecting: true,
+        isConnectionFailed: false,
+        isConnectionNotResponding: false,
+        isConnectionTimeout: false,
+      };
+      return _updateRuntimeById(id, updatedState, state);
+    }
+
+    case CONNECT_RUNTIME_NOT_RESPONDING: {
+      const { id } = action;
+      return _updateRuntimeById(id, { isConnectionNotResponding: true }, state);
+    }
+
+    case CONNECT_RUNTIME_CANCEL: {
+      const { id } = action;
+      const updatedState = {
+        isConnecting: false,
+        isConnectionFailed: false,
+        isConnectionNotResponding: false,
+        isConnectionTimeout: true,
+      };
+      return _updateRuntimeById(id, updatedState, state);
+    }
+
+    case CONNECT_RUNTIME_SUCCESS: {
+      const { id, runtimeDetails, type } = action.runtime;
+
+      // Update the remoteClientManager with the connected runtime.
+      const client = runtimeDetails.clientWrapper.client;
+      const runtimeInfo = runtimeDetails.info;
+      remoteClientManager.setClient(id, type, client, runtimeInfo);
+
+      const updatedState = {
+        isConnecting: false,
+        isConnectionFailed: false,
+        isConnectionNotResponding: false,
+        isConnectionTimeout: false,
+        runtimeDetails,
+      };
+      return _updateRuntimeById(id, updatedState, state);
+    }
+
+    case CONNECT_RUNTIME_FAILURE: {
+      const { id } = action;
+      const updatedState = {
+        isConnecting: false,
+        isConnectionFailed: true,
+        isConnectionNotResponding: false,
+        isConnectionTimeout: false,
+      };
+      return _updateRuntimeById(id, updatedState, state);
+    }
+
+    case DISCONNECT_RUNTIME_SUCCESS: {
+      const { id, type } = action.runtime;
+      remoteClientManager.removeClient(id, type);
+      return _updateRuntimeById(id, { runtimeDetails: null }, state);
+    }
+
+    case SELECTED_RUNTIME_ID_UPDATED: {
+      const selectedRuntimeId = action.runtimeId || null;
+      return Object.assign({}, state, { selectedRuntimeId });
+    }
+
+    case UPDATE_CONNECTION_PROMPT_SETTING_SUCCESS: {
+      const { connectionPromptEnabled } = action;
+      const { id: runtimeId } = action.runtime;
+      const runtime = findRuntimeById(runtimeId, state);
+      const runtimeDetails = Object.assign({}, runtime.runtimeDetails, {
+        connectionPromptEnabled,
+      });
+      return _updateRuntimeById(runtimeId, { runtimeDetails }, state);
+    }
+
+    case REMOTE_RUNTIMES_UPDATED: {
+      const { runtimes, runtimeType } = action;
+      const key = TYPE_TO_RUNTIMES_KEY[runtimeType];
+      return Object.assign({}, state, {
+        [key]: runtimes,
+      });
+    }
+
+    case THIS_FIREFOX_RUNTIME_CREATED: {
+      const { runtime } = action;
+      return Object.assign({}, state, {
+        thisFirefoxRuntimes: [runtime],
+      });
+    }
+
+    default:
+      return state;
+  }
+}
+
+module.exports = {
+  RuntimesState,
+  runtimesReducer,
+};
diff --git a/devtools/client/aboutdebugging/src/reducers/ui-state.js b/devtools/client/aboutdebugging/src/reducers/ui-state.js
new file mode 100644
index 0000000000..771358eaac
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/reducers/ui-state.js
@@ -0,0 +1,115 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  ADB_ADDON_STATUS_UPDATED,
+  ADB_READY_UPDATED,
+  DEBUG_TARGET_COLLAPSIBILITY_UPDATED,
+  HIDE_PROFILER_DIALOG,
+  NETWORK_LOCATIONS_UPDATE_SUCCESS,
+  PROFILER_PAGE_CONTEXT,
+  SELECT_PAGE_SUCCESS,
+  SHOW_PROFILER_DIALOG,
+  SWITCH_PROFILER_CONTEXT,
+  TEMPORARY_EXTENSION_INSTALL_FAILURE,
+  TEMPORARY_EXTENSION_INSTALL_SUCCESS,
+  USB_RUNTIMES_SCAN_START,
+  USB_RUNTIMES_SCAN_SUCCESS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+function UiState(
+  locations = [],
+  debugTargetCollapsibilities = {},
+  showHiddenAddons = false
+) {
+  return {
+    adbAddonStatus: null,
+    debugTargetCollapsibilities,
+    isAdbReady: false,
+    isScanningUsb: false,
+    networkLocations: locations,
+    profilerContext: PROFILER_PAGE_CONTEXT.DEVTOOLS_REMOTE,
+    selectedPage: null,
+    showProfilerDialog: false,
+    showHiddenAddons,
+    temporaryInstallError: null,
+  };
+}
+
+function uiReducer(state = UiState(), action) {
+  switch (action.type) {
+    case ADB_ADDON_STATUS_UPDATED: {
+      const { adbAddonStatus } = action;
+      return Object.assign({}, state, { adbAddonStatus });
+    }
+
+    case ADB_READY_UPDATED: {
+      const { isAdbReady } = action;
+      return Object.assign({}, state, { isAdbReady });
+    }
+
+    case DEBUG_TARGET_COLLAPSIBILITY_UPDATED: {
+      const { isCollapsed, key } = action;
+      const debugTargetCollapsibilities = new Map(
+        state.debugTargetCollapsibilities
+      );
+      debugTargetCollapsibilities.set(key, isCollapsed);
+      return Object.assign({}, state, { debugTargetCollapsibilities });
+    }
+
+    case NETWORK_LOCATIONS_UPDATE_SUCCESS: {
+      const { locations } = action;
+      return Object.assign({}, state, { networkLocations: locations });
+    }
+
+    case SELECT_PAGE_SUCCESS: {
+      const { page } = action;
+      return Object.assign({}, state, { selectedPage: page });
+    }
+
+    case SHOW_PROFILER_DIALOG: {
+      return Object.assign({}, state, {
+        showProfilerDialog: true,
+        // Always start in the devtools-remote view.
+        profilerContext: "devtools-remote",
+      });
+    }
+
+    case HIDE_PROFILER_DIALOG: {
+      return Object.assign({}, state, { showProfilerDialog: false });
+    }
+
+    case SWITCH_PROFILER_CONTEXT: {
+      const { profilerContext } = action;
+      return Object.assign({}, state, { profilerContext });
+    }
+
+    case USB_RUNTIMES_SCAN_START: {
+      return Object.assign({}, state, { isScanningUsb: true });
+    }
+
+    case USB_RUNTIMES_SCAN_SUCCESS: {
+      return Object.assign({}, state, { isScanningUsb: false });
+    }
+
+    case TEMPORARY_EXTENSION_INSTALL_SUCCESS: {
+      return Object.assign({}, state, { temporaryInstallError: null });
+    }
+
+    case TEMPORARY_EXTENSION_INSTALL_FAILURE: {
+      const { error } = action;
+      return Object.assign({}, state, { temporaryInstallError: error });
+    }
+
+    default:
+      return state;
+  }
+}
+
+module.exports = {
+  UiState,
+  uiReducer,
+};
diff --git a/devtools/client/aboutdebugging/src/types/debug-target.js b/devtools/client/aboutdebugging/src/types/debug-target.js
new file mode 100644
index 0000000000..c2f419082a
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/types/debug-target.js
@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+const {
+  DEBUG_TARGETS,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+const extensionTargetDetails = {
+  // actor ID for this extention.
+  actor: PropTypes.string.isRequired,
+  location: PropTypes.string.isRequired,
+  // error message forwarded from the WebExtensions internals if terminating the background script failed.
+  lastTerminateBackgroundScriptError: PropTypes.string,
+  // manifestURL points to the manifest.json file. This URL is only valid when debugging
+  // local extensions so it might be null.
+  manifestURL: PropTypes.string,
+  // error message forwarded from the addon manager during reloading temporary extension.
+  reloadError: PropTypes.string,
+  // unique extension id.
+  uuid: PropTypes.string.isRequired,
+  // warning messages forwarded from the addon manager.
+  warnings: PropTypes.arrayOf(PropTypes.string).isRequired,
+};
+
+const processTargetDetails = {
+  // Description for the process.
+  description: PropTypes.string.isRequired,
+};
+
+const tabTargetDetails = {
+  // the url of the tab.
+  url: PropTypes.string.isRequired,
+};
+
+const workerTargetDetails = {
+  // (service worker specific) one of "LISTENING", "NOT_LISTENING". undefined otherwise.
+  fetch: PropTypes.string,
+  // front for the ServiceWorkerRegistration related to this service worker.
+  registrationFront: PropTypes.object,
+  // (service worker specific) scope of the service worker registration.
+  scope: PropTypes.string,
+  // (service worker specific) one of "RUNNING", "REGISTERING", "STOPPED".
+  status: PropTypes.string,
+};
+
+const debugTarget = {
+  // details property will contain a type-specific object.
+  details: PropTypes.oneOfType([
+    PropTypes.shape(extensionTargetDetails),
+    PropTypes.shape(processTargetDetails),
+    PropTypes.shape(tabTargetDetails),
+    PropTypes.shape(workerTargetDetails),
+  ]).isRequired,
+  // icon to display for the debug target.
+  icon: PropTypes.string.isRequired,
+  // unique id for the target (unique in the scope of the application lifecycle).
+  // - extensions: {String} extension id (for instance "someextension@mozilla.org")
+  // - tabs: {Number} browserId
+  // - workers: {String} id for the WorkerTargetActor corresponding to the worker
+  id: PropTypes.oneOfType([PropTypes.number, PropTypes.string]).isRequired,
+  // display name for the debug target.
+  name: PropTypes.string.isRequired,
+  // one of "extension", "tab", "worker", "process".
+  type: PropTypes.oneOf(Object.values(DEBUG_TARGETS)).isRequired,
+};
+
+exports.debugTarget = PropTypes.shape(debugTarget);
diff --git a/devtools/client/aboutdebugging/src/types/index.js b/devtools/client/aboutdebugging/src/types/index.js
new file mode 100644
index 0000000000..288a063be1
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/types/index.js
@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const debugTargetTypes = require("resource://devtools/client/aboutdebugging/src/types/debug-target.js");
+const runtimeTypes = require("resource://devtools/client/aboutdebugging/src/types/runtime.js");
+const uiTypes = require("resource://devtools/client/aboutdebugging/src/types/ui.js");
+
+module.exports = Object.assign(
+  {},
+  {
+    ...debugTargetTypes,
+    ...runtimeTypes,
+    ...uiTypes,
+  }
+);
diff --git a/devtools/client/aboutdebugging/src/types/moz.build b/devtools/client/aboutdebugging/src/types/moz.build
new file mode 100644
index 0000000000..a58a6e0e28
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/types/moz.build
@@ -0,0 +1,10 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "debug-target.js",
+    "index.js",
+    "runtime.js",
+    "ui.js",
+)
diff --git a/devtools/client/aboutdebugging/src/types/runtime.js b/devtools/client/aboutdebugging/src/types/runtime.js
new file mode 100644
index 0000000000..cef9ace204
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/types/runtime.js
@@ -0,0 +1,164 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+const {
+  ClientWrapper,
+} = require("resource://devtools/client/aboutdebugging/src/modules/client-wrapper.js");
+const {
+  COMPATIBILITY_STATUS,
+} = require("resource://devtools/client/shared/remote-debugging/version-checker.js");
+
+const runtimeInfo = {
+  // device name which is running the runtime,
+  // unavailable on this-firefox runtime
+  deviceName: PropTypes.string,
+
+  // icon which represents the kind of runtime
+  icon: PropTypes.string.isRequired,
+
+  // name of runtime such as "Firefox Nightly"
+  name: PropTypes.string.isRequired,
+
+  // operating system on which the runtime runs such as "Android", "Linux"
+  os: PropTypes.string.isRequired,
+
+  // runtime type, for instance "network", "usb" ...
+  type: PropTypes.string.isRequired,
+
+  // version of runtime
+  version: PropTypes.string.isRequired,
+};
+
+const compatibilityReport = {
+  // build ID for the current runtime (date formatted as yyyyMMdd eg "20193101")
+  localID: PropTypes.string.isRequired,
+
+  // "platform" version for the current runtime (eg "67.0a1")
+  localVersion: PropTypes.string.isRequired,
+
+  // minimum "platform" version supported for remote debugging by the current runtime
+  minVersion: PropTypes.string.isRequired,
+
+  // build ID for the target runtime (date formatted as yyyyMMdd eg "20193101")
+  runtimeID: PropTypes.string.isRequired,
+
+  // "platform" version for the target runtime (eg "67.0a1")
+  runtimeVersion: PropTypes.string.isRequired,
+
+  // report result, either COMPATIBLE, TOO_OLD or TOO_RECENT
+  status: PropTypes.oneOf(Object.values(COMPATIBILITY_STATUS)).isRequired,
+};
+exports.compatibilityReport = PropTypes.shape(compatibilityReport);
+
+const runtimeDetails = {
+  // True if this runtime supports debugging service workers.
+  // This might be undefined when connecting to runtimes older than Fx 66
+  canDebugServiceWorkers: PropTypes.bool,
+
+  // ClientWrapper built using a DevToolsClient for the runtime
+  clientWrapper: PropTypes.instanceOf(ClientWrapper).isRequired,
+
+  // compatibility report to check if the target runtime is in range of the backward
+  // compatibility policy for DevTools remote debugging.
+  compatibilityReport: PropTypes.shape(compatibilityReport).isRequired,
+
+  // reflect devtools.debugger.prompt-connection preference of this runtime
+  connectionPromptEnabled: PropTypes.bool.isRequired,
+
+  // runtime information
+  info: PropTypes.shape(runtimeInfo).isRequired,
+
+  // True if service workers should be available in the target runtime. Service workers
+  // can be disabled via preferences or if the runtime runs in fully private browsing
+  // mode.
+  serviceWorkersAvailable: PropTypes.bool.isRequired,
+};
+exports.runtimeDetails = PropTypes.shape(runtimeDetails);
+
+const networkRuntimeConnectionParameter = {
+  // host name of devtools server to connect
+  host: PropTypes.string.isRequired,
+
+  // port number of devtools server to connect
+  port: PropTypes.number.isRequired,
+};
+
+const usbRuntimeConnectionParameter = {
+  // device id
+  deviceId: PropTypes.string.isRequired,
+  // socket path to connect devtools server
+  socketPath: PropTypes.string.isRequired,
+};
+
+const runtimeExtra = {
+  // parameter to connect to devtools server
+  // unavailable on unavailable/unplugged runtimes
+  connectionParameters: PropTypes.oneOfType([
+    PropTypes.shape(networkRuntimeConnectionParameter),
+    PropTypes.shape(usbRuntimeConnectionParameter),
+  ]),
+
+  // device name
+  // unavailable on this-firefox and network-location runtimes
+  deviceName: PropTypes.string,
+
+  // version of the application coming from ADB, only available via USB. Useful for Fenix
+  // runtimes, because the version can't be retrieved from Service.appInfo.
+  adbPackageVersion: PropTypes.string,
+};
+
+const runtime = {
+  // unique id for the runtime
+  id: PropTypes.string.isRequired,
+
+  // object containing non standard properties that depend on the runtime type,
+  // unavailable on this-firefox runtime
+  extra: PropTypes.shape(runtimeExtra),
+
+  // this flag will be true when start to connect to the runtime, will be false after
+  // connected or has failures.
+  isConnecting: PropTypes.bool.isRequired,
+
+  // this flag will be true when the connection failed.
+  isConnectionFailed: PropTypes.bool.isRequired,
+
+  // will be true if connecting to runtime is taking time, will be false after connecting
+  // or failing.
+  isConnectionNotResponding: PropTypes.bool.isRequired,
+
+  // this flag will be true when the connection was timeout.
+  isConnectionTimeout: PropTypes.bool.isRequired,
+
+  // this flag will be true when the detected runtime is Fenix (Firefox Preview).
+  // Fenix need specific logic to get their display name, version and logos.
+  // Discussion ongoing in https://github.com/mozilla-mobile/fenix/issues/2016
+  isFenix: PropTypes.bool.isRequired,
+
+  // unavailable runtimes are placeholders for devices where the runtime has not been
+  // started yet. For instance an ADB device connected without a compatible runtime
+  // running.
+  isUnavailable: PropTypes.bool.isRequired,
+
+  // unplugged runtimes are placeholders for devices that are no longer available. For
+  // instance a USB device that was unplugged from the computer.
+  isUnplugged: PropTypes.bool.isRequired,
+
+  // display name of the runtime
+  name: PropTypes.string.isRequired,
+
+  // available after the connection to the runtime is established
+  // unavailable on disconnected runtimes
+  runtimeDetails: PropTypes.shape(runtimeDetails),
+
+  // runtime type, for instance "network", "usb" ...
+  type: PropTypes.string.isRequired,
+};
+
+/**
+ * Export type of runtime
+ */
+exports.runtime = PropTypes.shape(runtime);
diff --git a/devtools/client/aboutdebugging/src/types/ui.js b/devtools/client/aboutdebugging/src/types/ui.js
new file mode 100644
index 0000000000..68daaaa5d2
--- /dev/null
+++ b/devtools/client/aboutdebugging/src/types/ui.js
@@ -0,0 +1,85 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+const {
+  ADB_ADDON_STATES,
+} = require("resource://devtools/client/shared/remote-debugging/adb/adb-addon.js");
+const {
+  DEBUG_TARGET_PANE,
+  PAGE_TYPES,
+} = require("resource://devtools/client/aboutdebugging/src/constants.js");
+
+function makeCollapsibilitiesType(isRequired) {
+  return (props, propName, componentName, _, propFullName) => {
+    if (isRequired && props[propName] === null) {
+      return new Error(
+        `Missing prop ${propFullName} marked as required in ${componentName}`
+      );
+    }
+
+    const error = new Error(
+      `Invalid prop ${propFullName} (${props[propName]}) supplied to ` +
+        `${componentName}. Collapsibilities needs to be a Map<DEBUG_TARGET_PANE, bool>`
+    );
+
+    const map = props[propName];
+
+    // check that the prop is a Map
+    if (!(map instanceof Map)) {
+      return error;
+    }
+
+    // check that the keys refer to debug target panes
+    const areKeysValid = [...map.keys()].every(x =>
+      Object.values(DEBUG_TARGET_PANE).includes(x)
+    );
+    // check that the values are boolean
+    const areValuesValid = [...map.values()].every(x => typeof x === "boolean");
+    // error if values or keys fail their checks
+    if (!areKeysValid || !areValuesValid) {
+      return error;
+    }
+
+    return null;
+  };
+}
+
+function makeLocationType(isRequired) {
+  return (props, propName, componentName, _, propFullName) => {
+    if (isRequired && props[propName] === null) {
+      return new Error(
+        `Missing prop ${propFullName} marked as required in ${componentName}`
+      );
+    }
+
+    // check that location is a string with a semicolon in it
+    if (!/\:/.test(props[propName])) {
+      return new Error(
+        `Invalid prop ${propFullName} (${props[propName]}) supplied to ` +
+          `${componentName}. Location needs to be a string with a host:port format`
+      );
+    }
+
+    return null;
+  };
+}
+
+const collapsibilities = makeCollapsibilitiesType(false);
+collapsibilities.isRequired = makeCollapsibilitiesType(true);
+
+const location = makeLocationType(false);
+location.isRequired = makeLocationType(true);
+
+module.exports = {
+  adbAddonStatus: PropTypes.oneOf(Object.values(ADB_ADDON_STATES)),
+  // a Map<DEBUG_TARGET_PANE, bool>, to flag collapsed/expanded status of the
+  // debug target panes
+  collapsibilities,
+  // a string with "host:port" format, used for network locations
+  location,
+  page: PropTypes.oneOf(Object.values(PAGE_TYPES)),
+};