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+# How to register an actor
+
+## Target-scoped actors vs. global actors
+
+Target-scoped actors are the most common types of actors. That's the type of actors you will most probably be adding.
+
+Target-scoped actors target a document, this could be a tab in Firefox or a remote document in Firefox for Android.
+
+Global actors however are for the rest, for things not related to any particular document but instead for things global to the whole Firefox/Chrome/Safari instance the toolbox is connected to (e.g. the preference actor).
+
+## The ActorRegistry.registerModule function
+
+To register a target-scoped actor:
+
+```
+ActorRegistry.registerModule("devtools/server/actors/webconsole", {
+  prefix: "console",
+  constructor: "WebConsoleActor",
+  type: { target: true }
+});
+```
+
+To register a global actor:
+
+```
+ActorRegistry.registerModule("devtools/server/actors/preference", {
+  prefix: "preference",
+  constructor: "PreferenceActor",
+  type: { global: true }
+});
+```
+
+If you are adding a new built-in actor, you should be registering it using `ActorRegistry.registerModule` in `addBrowserActors` or `addTargetScopedActors` in `/devtools/server/actors/utils/actor-registry.js`.
+
+## A note about lazy registration
+
+The `ActorRegistry` loads and creates all of the actors lazily to keep the initial memory usage down (which is extremely important on lower end devices).
+
+It becomes especially important when debugging pages with e10s when there are more than one process, because that's when we need to spawn a `DevToolsServer` per process (it may not be immediately obvious that the server in the main process is mostly only here for piping messages to the actors in the child process).