diff --git a/files/en-us/mozilla/add-ons/webextensions/api/storage/onchanged/index.md b/files/en-us/mozilla/add-ons/webextensions/api/storage/onchanged/index.md
index 9d12c6ed6c4f1ce..f20e344a10be860 100644
--- a/files/en-us/mozilla/add-ons/webextensions/api/storage/onchanged/index.md
+++ b/files/en-us/mozilla/add-ons/webextensions/api/storage/onchanged/index.md
@@ -15,7 +15,9 @@ browser-compat: webextensions.api.storage.onChanged
 ---
 {{AddonSidebar()}}
 
-Fired when one or more items change.
+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.
+
+When this event is triggered by {{WebExtAPIRef('storage.StorageArea.set','storageArea.set')}}, it's possible to receive a callback when there is no change to the underlying data. Also, the information returned includes all keys within the storage area {{WebExtAPIRef('storage.StorageArea.set','storageArea.set')}} ran against. The extension can determine the changes that occurred by examining the content of the `changes` argument received by the `onChanged` listeners.
 
 ## Syntax
 
@@ -40,10 +42,10 @@ Events have three functions:
 
 - `callback`
 
-  - : Function that will be called when this event occurs. The function will be passed the following arguments:
+  - : The function called when this event occurs. The function is passed these arguments:
 
     - `changes`
-      - : `object`. Object describing the change. This contains one property for each key that changed. The name of the property is the name of the key that changed, and its value is a {{WebExtAPIRef('storage.StorageChange')}} object describing the change to that item.
+      - : `object`. Object describing the change. This object contains properties for all the keys in the storage area included in the {{WebExtAPIRef('storage.StorageArea.set','storageAred.set')}} call, even if key values are unchanged. 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.