This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The claim() method of the Clients allows an active service worker to set itself as the controller for all clients within its scope. This triggers a "controllerchange" event on navigator.serviceWorker in any clients that become controlled by this service worker.

When a service worker is initially registered, pages won't use it until they next load. The claim() method causes those pages to be controlled immediately. Be aware that this results in your service worker controlling pages that loaded regularly over the network, or possibly via a different service worker.


await clients.claim();




A Promise for void.


The following example uses claim() inside service worker's "activate" event listener so that clients loaded in the same scope do not need to be reloaded before their fetches will go through this service worker.

self.addEventListener('activate', event => {


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

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Chrome Full support 42Edge ? Firefox Full support 44
Full support 44
Notes Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR).
IE No support NoOpera Full support 29Safari No support NoWebView Android Full support 42Chrome Android Full support 42Edge Mobile ? Firefox Android Full support 44Opera Android Full support 29Safari iOS No support NoSamsung Internet Android Full support 4.0


Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.

See also

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