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 ServiceWorker interface of the ServiceWorker 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 in the property, and the ServiceWorkerContainer.controller property — this is a service worker that activated and controlling the page (the service worker has been successfully registered, and the controlled page has been reloaded.)

The ServiceWorker interface is dispatched a set of lifecycle events — install and activate — and functional events including fetch. A ServiceWorker object has an associated ServiceWorker.state, related to its lifecycle.


The ServiceWorker interface inherits properties from its parent, Worker.

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: installing, installed, activating, activated, or redundant.

Event handlers

ServiceWorker.onstatechange Read only
An EventListener property called whenever an event of type statechange is fired; it is basically fired anytime the ServiceWorker.state changes.


The ServiceWorker interface inherits methods from its parent, Worker, with the exception of Worker.terminate — this should not be accessible from service workers.


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.

if ('serviceWorker' in navigator) {
    navigator.serviceWorker.register('service-worker.js', {
        scope: './'
    }).then(function (registration) {
        var 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 ( {
            serviceWorker =;
            document.querySelector('#kind').textContent = 'active';
        if (serviceWorker) {
            // logState(serviceWorker.state);
            serviceWorker.addEventListener('statechange', function (e) {
                // logState(;
    }).catch (function (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.


Specification Status Comment
Service Workers
The definition of 'ServiceWorker' 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 Android Webview Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support No support No 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


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API Draft Interface Offline offline Service Workers ServiceWorker Workers