The claim() method of the Clients interface 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();



Return value

A Promise that resolves to undefined.


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

BCD tables only load in the browser

See also