This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The clientId read-only property of the FetchEvent returns the id of the Client that the current service worker is controlling.

The Clients.get() method could then be passed this ID to retrieve the associated client.


var myClientId = FetchEvent.clientId;


A DOMString that represents the client ID.


self.addEventListener('fetch', function(event) {


Specification Status Comment
Service Workers
The definition of 'clientId' in that specification.
Working Draft Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 49.0 45.0 (45.0)[1] No support ? No support
Feature Android Android Webview Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support No support 49.0 45.0 (45.0) (Yes) No support ? No support 49.0

[1] Service workers (and Push) have been disabled in the Firefox 45 Extended Support Release (ESR.)

See also

Document Tags and Contributors

 Contributors to this page: chrisdavidmills, dgashmdn
 Last updated by: chrisdavidmills,