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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 activeWorker read-only property of the InstallEvent interface returns the ServiceWorker that is currently actively controlling the page.

This will return null if no active worker is already controlling the page.


var myActiveWorker = event.activeWorker


A ServiceWorker object.


self.addEventListener('install', function(event) {
  var myActiveWorker = event.activeWorker;


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 40.0 44.0 (44.0)[1] No support 24 No support
Feature Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support ? 44.0 (44.0) (Yes) No support ? No support 40.0

[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, Sebastianz, kscarfone
 Last updated by: chrisdavidmills,