ServiceWorker

Baseline Widely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2018.

* Some parts of this feature may have varying levels of support.

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

Note: This feature is available in Web Workers.

The ServiceWorker interface of the Service Worker API provides a reference to a service worker. Multiple browsing contexts (e.g., pages, workers, etc.) can be associated with the same service worker, each through a unique ServiceWorker object.

A ServiceWorker object is available via a number of properties:

The ServiceWorker.state property and statechange event can be used to check and observe changes in the lifecycle-state of the object's associated service worker. Related lifecycle events, such as install and activate are fired at the service worker itself.

Service workers allow static import of ECMAScript modules, if supported, using import. Dynamic import is disallowed by the specification — calling import() will throw.

Service workers can only be registered in the Window scope in some or all browsers, because the ServiceWorker object is not exposed to DedicatedWorkerGlobalScope and SharedWorkerGlobalScope. Check the browser compatibility for information.

EventTarget ServiceWorker

Instance properties

The ServiceWorker interface inherits properties from its parent, EventTarget.

ServiceWorker.scriptURL Read only

Returns the ServiceWorker serialized script URL defined as part of ServiceWorkerRegistration. The URL must be on the same origin as the document that registers the ServiceWorker.

ServiceWorker.state Read only

Returns the state of the service worker. It returns one of the following values: parsed, installing, installed, activating, activated, or redundant.

Instance methods

The ServiceWorker interface inherits methods from its parent, EventTarget.

ServiceWorker.postMessage()

Sends a message — consisting of any structured-cloneable JavaScript object — to the service worker. The message is transmitted to the service worker using a message event on its global scope.

Events

statechange

Fired when ServiceWorker.state changes.

error

Fired when an error happens inside the ServiceWorker object.

Examples

This code snippet is from the service worker registration-events sample (live demo). The code listens for any change in the ServiceWorker.state and returns its value.

js
if ("serviceWorker" in navigator) {
  navigator.serviceWorker
    .register("service-worker.js", {
      scope: "./",
    })
    .then((registration) => {
      let serviceWorker;
      if (registration.installing) {
        serviceWorker = registration.installing;
        document.querySelector("#kind").textContent = "installing";
      } else if (registration.waiting) {
        serviceWorker = registration.waiting;
        document.querySelector("#kind").textContent = "waiting";
      } else if (registration.active) {
        serviceWorker = registration.active;
        document.querySelector("#kind").textContent = "active";
      }
      if (serviceWorker) {
        // logState(serviceWorker.state);
        serviceWorker.addEventListener("statechange", (e) => {
          // logState(e.target.state);
        });
      }
    })
    .catch((error) => {
      // Something went wrong during registration. The service-worker.js file
      // might be unavailable or contain a syntax error.
    });
} else {
  // The current browser doesn't support service workers.
  // Perhaps it is too old or we are not in a Secure Context.
}

Specifications

Specification
Service Workers Nightly
# serviceworker-interface

Browser compatibility

desktop mobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
ServiceWorker
Chrome – Full support
Chrome 40 (Release date: 2015-01-21)
footnote Full support
Edge – Full support
Edge 17 (Release date: 2018-04-30)
footnote Full support
Firefox – Full support
Firefox 44 (Release date: 2016-01-26)
footnote Full support
Opera – Full support
Opera 27 (Release date: 2015-01-27)
footnote Full support
Safari – Full support
Safari 11.1 (Release date: 2018-04-12)
footnote Full support
Chrome Android – Full support
Chrome Android 40 (Release date: 2015-01-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 44 (Release date: 2016-01-26)
footnote Full support
Opera Android – Full support
Opera Android 27 (Release date: 2015-01-29)
footnote Full support
Safari on iOS – Full support
Safari on iOS 11.3 (Release date: 2018-03-29)
footnote Full support
Samsung Internet – Full support
Samsung Internet 4 (Release date: 2016-03-11)
footnote Full support
WebView Android – Full support
WebView Android 40 (Release date: 2015-01-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
Support for ECMAScript modules
Chrome – Full support
Chrome 91 (Release date: 2021-05-25)
footnote Full support
Edge – Full support
Edge 91 (Release date: 2021-05-27)
footnote Full support
Firefox – Full support
Firefox 147 (Release date: 2026-01-13)
footnote Full support
Opera – Full support
Opera 77 (Release date: 2021-06-09)
footnote Full support
Safari – Full support
Safari 15 (Release date: 2021-09-20)
footnote
footnote Nested workers support was introduced in Safari 15.5.
footnote Script loading in nested workers was introduced in Safari 16.4.
Chrome Android – Full support
Chrome Android 91 (Release date: 2021-05-25)
footnote Full support
Firefox for Android – Full support
Firefox for Android 147 (Release date: 2026-01-13)
footnote Full support
Opera Android – Full support
Opera Android 64 (Release date: 2021-05-25)
footnote Full support
Safari on iOS – Full support
Safari on iOS 15 (Release date: 2021-09-20)
footnote
footnote Nested workers support was introduced in Safari on iOS 15.5.
footnote Script loading in nested workers was introduced in Safari on iOS 16.4.
Samsung Internet – Full support
Samsung Internet 16 (Release date: 2021-11-25)
footnote Full support
WebView Android – Full support
WebView Android 91 (Release date: 2021-05-25)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
error event
Chrome – Full support
Chrome 40 (Release date: 2015-01-21)
footnote Full support
Edge – Full support
Edge 17 (Release date: 2018-04-30)
footnote Full support
Firefox – Full support
Firefox 44 (Release date: 2016-01-26)
footnote Full support
Opera – Full support
Opera 27 (Release date: 2015-01-27)
footnote Full support
Safari – Full support
Safari 11.1 (Release date: 2018-04-12)
footnote Full support
Chrome Android – Full support
Chrome Android 40 (Release date: 2015-01-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 44 (Release date: 2016-01-26)
footnote Full support
Opera Android – Full support
Opera Android 27 (Release date: 2015-01-29)
footnote Full support
Safari on iOS – Full support
Safari on iOS 11.3 (Release date: 2018-03-29)
footnote Full support
Samsung Internet – Full support
Samsung Internet 4 (Release date: 2016-03-11)
footnote Full support
WebView Android – Full support
WebView Android 40 (Release date: 2015-01-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
postMessage
Chrome – Full support
Chrome 40 (Release date: 2015-01-21)
footnote Full support
Edge – Full support
Edge 17 (Release date: 2018-04-30)
footnote Full support
Firefox – Full support
Firefox 44 (Release date: 2016-01-26)
footnote Full support
Opera – Full support
Opera 27 (Release date: 2015-01-27)
footnote Full support
Safari – Full support
Safari 11.1 (Release date: 2018-04-12)
footnote Full support
Chrome Android – Full support
Chrome Android 40 (Release date: 2015-01-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 44 (Release date: 2016-01-26)
footnote Full support
Opera Android – Full support
Opera Android 27 (Release date: 2015-01-29)
footnote Full support
Safari on iOS – Full support
Safari on iOS 11.3 (Release date: 2018-03-29)
footnote Full support
Samsung Internet – Full support
Samsung Internet 4 (Release date: 2016-03-11)
footnote Full support
WebView Android – Full support
WebView Android 40 (Release date: 2015-01-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
scriptURL
Chrome – Full support
Chrome 40 (Release date: 2015-01-21)
footnote Full support
Edge – Full support
Edge 17 (Release date: 2018-04-30)
footnote Full support
Firefox – Full support
Firefox 44 (Release date: 2016-01-26)
footnote Full support
Opera – Full support
Opera 27 (Release date: 2015-01-27)
footnote Full support
Safari – Full support
Safari 11.1 (Release date: 2018-04-12)
footnote Full support
Chrome Android – Full support
Chrome Android 40 (Release date: 2015-01-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 44 (Release date: 2016-01-26)
footnote Full support
Opera Android – Full support
Opera Android 27 (Release date: 2015-01-29)
footnote Full support
Safari on iOS – Full support
Safari on iOS 11.3 (Release date: 2018-03-29)
footnote Full support
Samsung Internet – Full support
Samsung Internet 4 (Release date: 2016-03-11)
footnote Full support
WebView Android – Full support
WebView Android 40 (Release date: 2015-01-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
state
Chrome – Full support
Chrome 40 (Release date: 2015-01-21)
footnote Full support
Edge – Full support
Edge 17 (Release date: 2018-04-30)
footnote Full support
Firefox – Full support
Firefox 44 (Release date: 2016-01-26)
footnote Full support
Opera – Full support
Opera 27 (Release date: 2015-01-27)
footnote Full support
Safari – Full support
Safari 11.1 (Release date: 2018-04-12)
footnote Full support
Chrome Android – Full support
Chrome Android 40 (Release date: 2015-01-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 44 (Release date: 2016-01-26)
footnote Full support
Opera Android – Full support
Opera Android 27 (Release date: 2015-01-29)
footnote Full support
Safari on iOS – Full support
Safari on iOS 11.3 (Release date: 2018-03-29)
footnote Full support
Samsung Internet – Full support
Samsung Internet 4 (Release date: 2016-03-11)
footnote Full support
WebView Android – Full support
WebView Android 40 (Release date: 2015-01-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support
statechange event
Chrome – Full support
Chrome 40 (Release date: 2015-01-21)
footnote Full support
Edge – Full support
Edge 17 (Release date: 2018-04-30)
footnote Full support
Firefox – Full support
Firefox 44 (Release date: 2016-01-26)
footnote Full support
Opera – Full support
Opera 27 (Release date: 2015-01-27)
footnote Full support
Safari – Full support
Safari 11.1 (Release date: 2018-04-12)
footnote Full support
Chrome Android – Full support
Chrome Android 40 (Release date: 2015-01-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 44 (Release date: 2016-01-26)
footnote Full support
Opera Android – Full support
Opera Android 27 (Release date: 2015-01-29)
footnote Full support
Safari on iOS – Full support
Safari on iOS 11.3 (Release date: 2018-03-29)
footnote Full support
Samsung Internet – Full support
Samsung Internet 4 (Release date: 2016-03-11)
footnote Full support
WebView Android – Full support
WebView Android 40 (Release date: 2015-01-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support
See implementation notes.

See also