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diff --git a/toolkit/components/extensions/ExtensionDNRLimits.sys.mjs b/toolkit/components/extensions/ExtensionDNRLimits.sys.mjs
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+++ b/toolkit/components/extensions/ExtensionDNRLimits.sys.mjs
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+/* 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/. */
+
+// TODO(Bug 1803370): consider allowing changing DNR limits through about:config prefs).
+
+/**
+ * The minimum number of static rules guaranteed to an extension across its
+ * enabled static rulesets. Any rules above this limit will count towards the
+ * global static rule limit.
+ */
+const GUARANTEED_MINIMUM_STATIC_RULES = 30000;
+
+/**
+ * The maximum number of static Rulesets an extension can specify as part of
+ * the "rule_resources" manifest key.
+ *
+ * NOTE: this limit may be increased in the future, see https://github.com/w3c/webextensions/issues/318
+ */
+const MAX_NUMBER_OF_STATIC_RULESETS = 50;
+
+/**
+ * The maximum number of static Rulesets an extension can enable at any one time.
+ *
+ * NOTE: this limit may be increased in the future, see https://github.com/w3c/webextensions/issues/318
+ */
+const MAX_NUMBER_OF_ENABLED_STATIC_RULESETS = 10;
+
+/**
+ * The maximum number of dynamic and session rules an extension can add.
+ * NOTE: in the Firefox we are enforcing this limit to the session and dynamic rules count separately,
+ * instead of enforcing it to the rules count for both combined as the Chrome implementation does.
+ *
+ * NOTE: this limit may be increased in the future, see https://github.com/w3c/webextensions/issues/319
+ */
+const MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES = 5000;
+
+/**
+ * The maximum number of regular expression rules that an extension can add.
+ * Session, dynamic and static rules have their own quota.
+ *
+ * TODO bug 1821033: Bump limit after optimizing regexFilter.
+ */
+const MAX_NUMBER_OF_REGEX_RULES = 1000;
+
+// TODO(Bug 1803370): allow extension to exceed the GUARANTEED_MINIMUM_STATIC_RULES limit.
+//
+// The maximum number of static rules exceeding the per-extension
+// GUARANTEED_MINIMUM_STATIC_RULES across every extensions.
+//
+// const MAX_GLOBAL_NUMBER_OF_STATIC_RULES = 300000;
+
+export const ExtensionDNRLimits = {
+  GUARANTEED_MINIMUM_STATIC_RULES,
+  MAX_NUMBER_OF_STATIC_RULESETS,
+  MAX_NUMBER_OF_ENABLED_STATIC_RULESETS,
+  MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES,
+  MAX_NUMBER_OF_REGEX_RULES,
+};