storage.sync

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 (e.g. via Firefox sync, or a Google account), across different devices.

For Firefox a user must have Add-ons checked under the "Sync Settings" options in "about:preferences".

Note that the implementation of storage.sync in Firefox relies on the Add-on ID. If you use storage.sync, you must set an ID for your extension using the browser_specific_settings manifest.json key.

The main use case of this API is to store preferences about your extension and allow the user to sync them to different profiles.

Storage quotas for sync data

The browser enforces limits on the amount of data each extension is allowed to store in the sync area:

If an extension attempts to store items that exceed these limits, the call to storage.sync.set() will be rejected with an error. An extension can use storage.sync.getBytesInUse() to find out how much of its maximum total quota it is currently using.

Methods

The sync object implements the methods defined on the storage.StorageArea type:

storage.StorageArea.get()

Retrieves one or more items from the storage area.

storage.StorageArea.getBytesInUse()

Gets the amount of storage space (in bytes) used one or more items being stored in the storage area.

storage.StorageArea.set()

Stores one or more items in the storage area. If the item already exists, its value will be updated.

storage.StorageArea.remove()

Removes one or more items from the storage area.

storage.StorageArea.clear()

Removes all items from the storage area.

Browser compatibility

Example extensions

• favourite-colour