--- a/toolkit/components/extensions/ext-browserSettings.js
+++ b/toolkit/components/extensions/ext-browserSettings.js
@@ -13,16 +13,18 @@ XPCOMUtils.defineLazyServiceGetter(this,
 
 Cu.import("resource://gre/modules/ExtensionPreferencesManager.jsm");
 
 const HOMEPAGE_OVERRIDE_SETTING = "homepage_override";
 const HOMEPAGE_URL_PREF = "browser.startup.homepage";
 const URL_STORE_TYPE = "url_overrides";
 const NEW_TAB_OVERRIDE_SETTING = "newTabURL";
 
+const PERM_DENY_ACTION = Services.perms.DENY_ACTION;
+
 const getSettingsAPI = (extension, name, callback, storeType, readOnly = false) => {
   return {
     async get(details) {
       return {
         levelOfControl: details.incognito ?
           "not_controllable" :
           await ExtensionPreferencesManager.getLevelOfControl(
             extension, name, storeType),
@@ -77,16 +79,26 @@ ExtensionPreferencesManager.addSetting("
     "image.animation_mode",
   ],
 
   setCallback(value) {
     return {[this.prefNames[0]]: value};
   },
 });
 
+ExtensionPreferencesManager.addSetting("webNotificationsDisabled", {
+  prefNames: [
+    "permissions.default.desktop-notification",
+  ],
+
+  setCallback(value) {
+    return {[this.prefNames[0]]: value ? PERM_DENY_ACTION : undefined};
+  },
+});
+
 this.browserSettings = class extends ExtensionAPI {
   getAPI(context) {
     let {extension} = context;
     return {
       browserSettings: {
         allowPopupsForUserEvents: getSettingsAPI(extension,
           "allowPopupsForUserEvents",
           () => {
@@ -109,12 +121,20 @@ this.browserSettings = class extends Ext
           () => {
             return Services.prefs.getCharPref("image.animation_mode");
           }),
         newTabPageOverride: getSettingsAPI(extension,
           NEW_TAB_OVERRIDE_SETTING,
           () => {
             return aboutNewTabService.newTabURL;
           }, URL_STORE_TYPE, true),
+        webNotificationsDisabled: getSettingsAPI(extension,
+          "webNotificationsDisabled",
+          () => {
+            let prefValue =
+              Services.prefs.getIntPref(
+                "permissions.default.desktop-notification", null);
+            return prefValue === PERM_DENY_ACTION;
+          }),
       },
     };
   }
 };

--- a/toolkit/components/extensions/schemas/browser_settings.json
+++ b/toolkit/components/extensions/schemas/browser_settings.json
@@ -44,12 +44,16 @@
       },
       "imageAnimationBehavior": {
         "$ref": "types.Setting",
         "description": "Controls the behaviour of image animation in the browser. This setting's value is of type ImageAnimationBehavior, defaulting to <code>normal</code>."
       },
       "newTabPageOverride": {
         "$ref": "types.Setting",
         "description": "Returns the value of the overridden new tab page. Read-only."
+      },
+      "webNotificationsDisabled": {
+        "$ref": "types.Setting",
+        "description": "Disables webAPI notifications."
       }
     }
   }
 ]

--- a/toolkit/components/extensions/test/xpcshell/test_ext_browserSettings.js
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_browserSettings.js
@@ -13,22 +13,26 @@ const {
   promiseStartupManager,
 } = AddonTestUtils;
 
 AddonTestUtils.init(this);
 
 createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "42");
 
 add_task(async function test_browser_settings() {
+  const PERM_DENY_ACTION = Services.perms.DENY_ACTION;
+  const PERM_UNKNOWN_ACTION = Services.perms.UNKNOWN_ACTION;
+
   // Create an object to hold the values to which we will initialize the prefs.
   const PREFS = {
     "browser.cache.disk.enable": true,
     "browser.cache.memory.enable": true,
     "dom.popup_allowed_events": Preferences.get("dom.popup_allowed_events"),
     "image.animation_mode": "none",
+    "permissions.default.desktop-notification": PERM_UNKNOWN_ACTION,
   };
 
   async function background() {
     browser.test.onMessage.addListener(async (msg, apiName, value) => {
       let apiObj = browser.browserSettings[apiName];
       await apiObj.set({value});
       browser.test.sendMessage("settingData", await apiObj.get({}));
     });
@@ -90,12 +94,23 @@ add_task(async function test_browser_set
     {"dom.popup_allowed_events": PREFS["dom.popup_allowed_events"]});
 
   for (let value of ["normal", "none", "once"]) {
     await testSetting(
       "imageAnimationBehavior", value,
       {"image.animation_mode": value});
   }
 
+  await testSetting(
+    "webNotificationsDisabled", true,
+    {"permissions.default.desktop-notification": PERM_DENY_ACTION});
+  await testSetting(
+    "webNotificationsDisabled", false,
+    {
+      // This pref is not defaulted on Android.
+      "permissions.default.desktop-notification":
+        AppConstants.MOZ_BUILD_APP !== "browser" ? undefined : PERM_UNKNOWN_ACTION,
+    });
+
   await extension.unload();
 
   await promiseShutdownManager();
 });