Secure context
This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

The StorageEstimate dictionary is used by the StorageManager to provide estimates of the size of a site's or application's data store and how much of it is in use. The estimate() method returns an object that conforms to this dictionary when its Promise resolves.

These values are only estimates for several reasons, including both performance and preventing storage capacity data from being used for fingerprinting purposes. See the individual property pages for details.


This dictionary currently always has both of the following properties defined.

quota Secure context
A numeric value which provides a conservative approximation of the total storage the user's device or computer has available for the site origin or Web app. It's possible that there's more than this amount of space available though you can't rely on that being the case.
usage Secure context
A numeric value approximating the amount of storage space currently being used by the site or Web app, out of the available space as indicated by quota.


Specification Status Comment
The definition of 'StorageEstimate' in that specification.
Living Standard Initial definition.

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Microsoft Edge Opera Safari (WebKit)
Basic support 55 57 (57) ? ? 42 ?
Feature Android Webview Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? 55 57.0 (57) ? 42 ?

See also

Document Tags and Contributors

Contributors to this page: chrisdavidmills, jpmedley, tomayac, Sheppy
Last updated by: chrisdavidmills,