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 possible 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

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support42 ?441 No29 No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support4242 ?4429 No4.0

1. Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR).

See also

Document Tags and Contributors

Contributors to this page: fscholz, jpmedley, jaffathecake, chrisdavidmills, riking, kscarfone
Last updated by: fscholz,