Fix several issues in webext storage docs

files/en-us/mozilla/add-ons/webextensions/api/storage/onchanged/index.md

@@ -6,10 +6,16 @@ browser-compat: webextensions.api.storage.onChanged
 sidebar: addonsidebar
 ---
 
-Fired when {{WebExtAPIRef('storage.StorageArea.set','storageArea.set')}}, {{WebExtAPIRef('storage.StorageArea.remove','storageArea.remove')}}, or {{WebExtAPIRef('storage.StorageArea.clear','storageArea.clear')}} executes against a storage area, returning details of only changed keys. A callback is called only when there are changes to the underlying data.
+Fires when one or more items in any of the {{WebExtAPIRef('storage.StorageArea', 'storage areas'}} changes.
+If you only need to listen for changes in one storage area, use {{WebExtAPIRef('storage.StorageArea.onChanged')}} instead.
+
+Fired when {{WebExtAPIRef('storage.StorageArea.set','storageArea.set')}}, {{WebExtAPIRef('storage.StorageArea.remove','storageArea.remove')}}, or {{WebExtAPIRef('storage.StorageArea.clear','storageArea.clear')}} executes against any of the {{WebExtAPIRef('storage.StorageArea', 'storage areas'}}.
+
+> [!NOTE]
+> In Firefox, the listener receives all the keys from a storage area where {{WebExtAPIRef('storage.StorageArea.set','storageArea.set')}} executes. The listener may be invoked when there is no change to the data. To find details of the changed items, examine each key's {{WebExtAPIRef('storage.StorageChange')}} object. See [Firefox bug 1833153](https://bugzil.la/1833153).
 
 > [!NOTE]
-> In Firefox, the information returned includes all keys within the storage area {{WebExtAPIRef('storage.StorageArea.set','storageArea.set')}} ran against whether they changed or not. Also, a callback may be invoked when there is no change to the underlying data. Details of the changed items are found by examining each returned key's {{WebExtAPIRef('storage.StorageChange')}} object. See [Firefox bug 1833153](https://bugzil.la/1833153).
+> Firefox does not fire this event for changes to `storage.managed` because managed storage is only read on browser startup (from the [JSON manifest (native manifest) file](/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_manifests#managed_storage_manifests) or [`3rdparty` enterprise policy](https://mozilla.github.io/policy-templates/#3rdparty)).
 
 ## Syntax
 
@@ -37,7 +43,7 @@ Events have three functions:
     - `changes`
       - : `object`. Object describing the change. The name of each property is the name of each key. The value of each key is a {{WebExtAPIRef('storage.StorageChange')}} object describing the change to that item.
     - `areaName`
-      - : `string`. The name of the storage area (`"sync"`, `"local"`, or `"managed"`) to which the changes were made.
+      - : `string`. The name of the storage area (`"local"`, `"managed"`, `"session"`, or `"sync"`) to which the changes were made.
 
 ## Examples
 

files/en-us/mozilla/add-ons/webextensions/api/storage/storagearea/index.md

@@ -6,7 +6,14 @@ browser-compat: webextensions.api.storage.StorageArea
 sidebar: addonsidebar
 ---
 
-StorageArea is an object representing a storage area.
+StorageArea is an object representing a storage area. This documentation describes the common interface of these concrete implementations:
+
+- {{WebExtAPIRef("storage.local")}}
+- {{WebExtAPIRef("storage.managed")}}
+- {{WebExtAPIRef("storage.session")}}
+- {{WebExtAPIRef("storage.sync")}}
+
+`storage.StorageArea` is not an API object; it is a mechanism for describing the concrete APIs.
 
 ## Type
 

files/en-us/mozilla/add-ons/webextensions/api/storage/storagearea/onchanged/index.md

@@ -6,12 +6,13 @@ browser-compat: webextensions.api.storage.StorageArea.onChanged
 sidebar: addonsidebar
 ---
 
-Fires when one or more items in a storage area change, returning details for the keys that changed. Compared to {{WebExtAPIRef("storage.onChanged")}}, this event enables you to listen for changes in one of the storage areas: `local`, `managed`, `session`, and `sync`.
+Fires when one or more items in a storage area change. Compared to {{WebExtAPIRef("storage.onChanged")}}, this event enables you to listen for changes in one of the storage areas: `local`, `managed`, `session`, or `sync`.
 
 > [!NOTE]
-> In Firefox, the information returned includes all keys within the storage area. Also, the callback may be invoked when there is no change to the underlying data. Details of the changed items are found by examining each returned key's {{WebExtAPIRef('storage.StorageChange')}} object. See [Firefox bug 1833153](https://bugzil.la/1833153).
->
-> Firefox only loads changes to managed storage content (from the [JSON manifest (native manifest) file](/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_manifests#managed_storage_manifests) or [`3rdparty` enterprise policy](https://mozilla.github.io/policy-templates/#3rdparty)), when it restarts. Therefore, this event never triggers in Firefox.
+> In Firefox, the listener receives all the keys from a storage area where {{WebExtAPIRef('storage.StorageArea.set','storageArea.set')}} executes. The listener may also be invoked when there is no change to the data. To find details of the changed items, examine each key's {{WebExtAPIRef('storage.StorageChange')}} object. See [Firefox bug 1833153](https://bugzil.la/1833153).
+
+> [!NOTE]
+> Firefox does not fire this event for changes to `storage.managed` because managed storage is only read on browser startup (from the [JSON manifest (native manifest) file](/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_manifests#managed_storage_manifests) or [`3rdparty` enterprise policy](https://mozilla.github.io/policy-templates/#3rdparty)).
 
 ## Syntax
 

files/en-us/mozilla/add-ons/webextensions/api/storage/storagearea/setaccesslevel/index.md

@@ -8,11 +8,10 @@ sidebar: addonsidebar
 
 Sets the access level for the storage area.
 
-This method is only supported for the `storage.session` StorageArea.
+Use this method to:
 
-Unlike other storage areas, `storage.session` is only available to privileged (trusted) extension contexts. This `setAccessLevel` method is used to expose the session storage area to content scripts too. By default, all other storage areas are exposed to all extension contexts, including content scripts.
-
-This is an asynchronous function that returns a [`Promise`](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise).
+- Expose the `session` storage area to content scripts. Unlike other storage areas, by default, `storage.session` is only available to privileged (trusted) extension contexts by default.
+- Restrict content scripts' access to `local`, `managed`, and `sync` storage areas. By default, these storage areas are exposed to all extension contexts, including content scripts.
 
 ## Syntax
 
@@ -22,7 +21,7 @@ await browser.storage.<storageType>.setAccessLevel(
 )
 ```
 
-Where `<storageType>` is the {{WebExtAPIRef("storage.session")}} storage type.
+Where `<storageType>` is any of the storage types: {{WebExtAPIRef("storage.local")}}, {{WebExtAPIRef("storage.managed")}}, {{WebExtAPIRef("storage.session")}}, or {{WebExtAPIRef("storage.sync")}}.
 
 ### Parameters
 

files/en-us/mozilla/add-ons/webextensions/api/storage/storagechange/index.md

@@ -7,6 +7,7 @@ sidebar: addonsidebar
 ---
 
 `StorageChange` is an object representing a change to a storage area.
+Objects of this type are received by {{WebExtAPIRef("storage.onChanged")}} and {{WebExtAPIRef("storage.StorageArea.onChanged")}} event listeners.
 
 ## Type