MDN wants to learn about developers like you:



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

This is an asynchronous function that returns a Promise.


var gettingSpace =<storageType>.getBytesInUse(
  keys                      // null, string, or array of strings

<storageType> will be one of the writable storage types — storage.sync or storage.local.


A key (string) or keys (an array of strings) to identify the item(s) whose storage space you want to retrieve. If an empty string or array is passed in, 0 will be returned. If you pass null here, the function will return the space used by the entire storage area.

Return value

A Promise that will be fulfilled with an integer, bytesUsed, representing the storage space used by the objects that were specified in keys. If the operation failed, the promise will be rejected with an error message.

Browser compatibility

ChromeEdgeFirefoxFirefox for AndroidOpera
Basic support Yes Yes No No33


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.

Document Tags and Contributors

 Contributors to this page: wbamberg, Makyen, chrisdavidmills
 Last updated by: wbamberg,