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

The parameter passed into the oninstall handler, the InstallEvent interface represents an install action that is dispatched on the ServiceWorkerGlobalScope of a ServiceWorker. As a child of ExtendableEvent, it ensures that functional events such as FetchEvent are not dispatched during installation.

This interface inherits from the ExtendableEvent interface.


Creates a new InstallEvent object.


Inherits properties from its ancestor, Event.

InstallEvent.activeWorker Read only
Returns the ServiceWorker that is currently controlling the page.


Inherits methods from its parent, ExtendableEvent.


This code snippet is from the service worker prefetch sample (see prefetch running live.) The code calls ExtendableEvent.waitUntil() in ServiceWorkerGlobalScope.oninstall and delays treating the ServiceWorkerRegistration.installing worker as installed until the passed promise resolves successfully. The promise resolves when all resources have been fetched and cached, or when any exception occurs.

The code snippet also shows a best practice for versioning caches used by the service worker. Although this example has only one cache, you can use this approach for multiple caches. The code maps a shorthand identifier for a cache to a specific, versioned cache name.

Note: Logging statements are visible in Google Chrome via the "Inspect" interface for the relevant service worker accessed via chrome://serviceworker-internals.

  prefetch: 'prefetch-cache-v' + CACHE_VERSION

self.addEventListener('install', function(event) {
  var urlsToPrefetch = [

console.log('Handling install event. Resources to pre-fetch:', urlsToPrefetch);

    caches.open(CURRENT_CACHES['prefetch']).then(function(cache) {
      cache.addAll(urlsToPrefetch.map(function(urlToPrefetch) {
        return new Request(urlToPrefetch, {mode: 'no-cors'});
      })).then(function() {
        console.log('All resources have been fetched and cached.');
    }).catch(function(error) {
      console.error('Pre-fetching failed:', error);


Specification Status Comment
Service Workers Working Draft As of May 2015, the install event is an instance of ExtendableEvent rather than a child of it.

Browser compatibilityUpdate compatibility data on GitHub

Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 40 ? 44
Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR).
No 27 No
InstallEvent() constructor. 40 ? 44
Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR).
No 27 No
activeWorker 40 ? 44
Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR).
No 27 No
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support 40 40 ? 44 27 No 4.0
InstallEvent() constructor. 40 40 ? 44 27 No 4.0
activeWorker 40 40 ? 44 27 No 4.0

See also

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