/Web APIs


Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

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.


InstallEvent() Deprecated Non-standard

Creates a new InstallEvent object.

Instance properties

Inherits properties from its ancestor, Event.

InstallEvent.activeWorker Read only Deprecated Non-standard

Returns the ServiceWorker that is currently controlling the page.

Instance methods

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.

const CACHE_VERSION = 1;
  prefetch: `prefetch-cache-v${CACHE_VERSION}`,

self.addEventListener("install", (event) => {
  const urlsToPrefetch = [

    "Handling install event. Resources to pre-fetch:",

      .then((cache) => {
        return cache
            urlsToPrefetch.map((urlToPrefetch) => {
              return new Request(urlToPrefetch, { mode: "no-cors" });
          .then(() => {
            console.log("All resources have been fetched and cached.");
      .catch((error) => {
        console.error("Pre-fetching failed:", error);

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
InstallEvent 40 79 44 No 27 No 40 40 44 27 No 4.0
InstallEvent 40 17 44 No 27 No 40 40 44 27 No 4.0
activeWorker 40 17 44 No 27 No 40 40 44 27 No 4.0

See also

© 2005–2023 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.