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Enables WebExtensions to store and retrieve data, and listen for changes to stored items.

The storage system is based on the Web Storage API, with a few differences.

To use this API you need to include the "storage" permission in your manifest.json file. Each WebExtension has its own storage area, which can be split into different types of storage.

Although this API is similar to Window.localStorage it is recommended that you don't use Window.localStorage in add-on code. Firefox will clear data stored by add-ons using the localStorage API in various scenarios where users clear their browsing history and data for privacy reasons, while data saved using the storage.local API will be correctly persisted in these scenarios.


An object representing a storage area.
An object representing a change to a storage area.


storage has three properties, which represent the different types of available storage area.

Represents the sync storage area. Items in sync storage are synced by the browser, and are available across all instances of that browser that the user is logged into, across different devices.
Represents the local storage area. Items in local storage are local to the machine the extension was installed on.
Represents the managed storage area. Items in managed storage are set by the domain administrator and are read-only for the extension. Trying to modify this namespace results in an error.


Fired when one or more items change in a storage area.

Browser compatibility

Chrome Edge Firefox Firefox for Android Opera
StorageArea Yes Yes 45.0 48.0 33
StorageArea.clear Yes Yes 45.0 48.0 33
StorageArea.get Yes Yes 45.0 48.0 33
StorageArea.getBytesInUse Yes Yes No No 33
StorageArea.remove Yes Yes 45.0 48.0 33
StorageArea.set Yes Yes * 45.0 48.0 33
StorageChange Yes Yes 45.0 48.0 33
local Yes Yes 45.0 * 48.0 33
managed Yes No No No No
onChanged Yes Yes 45.0 48.0 33
sync Yes No 53.0 53.0 No

Edge incompatibilities

Promises are not supported in Edge. Use callbacks instead.

Chrome incompatibilities


Example add-ons


This API is based on Chromium's API. This documentation is derived from storage.json in the Chromium code.

Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.

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