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

The register() method of the ServiceWorkerContainer interface creates or updates a ServiceWorkerRegistration for the given scriptURL.

If successful, a service worker registration ties the provided script URL to a scope, which is subsequently used for navigation matching. You can call this method unconditionally from the controlled page. I.e., you don't need to first check whether there's an active registration.

There is frequent confusion surrounding the meaning and use of scope. Since a service worker can't have a scope broader than its own location, only use the scope option when you need a scope that is narrower than the default.


ServiceWorkerContainer.register(scriptURL, options)
  .then(function(ServiceWorkerRegistration) { ... });


The URL of the service worker script. The registered service worker file needs to have a valid JavaScript MIME type.
options Optional
An object containing registration options. Currently available options are:
  • scope: A USVString representing a URL that defines a service worker's registration scope; that is, what range of URLs a service worker can control. This is usually a relative URL. It is relative to the base URL of the application. By default, the scope value for a service worker registration is set to the directory where the service worker script is located. See the Examples section for more information on how it works.

Return value

A Promise that resolves with a ServiceWorkerRegistration object.


The examples described here should be taken together to get a better understanding of how service workers scope applies to a page.

The following example uses the default value of scope (by omitting it). The service worker in this case will control example.com/index.html as well as pages underneath it, like example.com/product/description.html.

if ('serviceWorker' in navigator) {
  // Register a service worker hosted at the root of the
  // site using the default scope.
  navigator.serviceWorker.register('/sw.js').then(function(registration) {
    console.log('Service worker registration succeeded:', registration);
  }, /*catch*/ function(error) {
    console.log('Service worker registration failed:', error);
} else {
  console.log('Service workers are not supported.');

The following code, if included in a page at the root of a site, would apply to exactly the same pages as the example above. Remember the scope, when included, uses the page's location as its base. Alternatively, if this code were included in a page at example.com/product/description.html, the scope of './' would mean that the service worker only applies to resources under example.com/product. If I needed to register a service worker on example.com/product/description.html that applied to all of example.com, I would leave off the scope as above.

if ('serviceWorker' in navigator) {
  // Register a service worker hosted at the root of the
  // site using a more restrictive scope.
  navigator.serviceWorker.register('/sw.js', {scope: './'}).then(function(registration) {
    console.log('Service worker registration succeeded:', registration);
  }, /*catch*/ function(error) {
    console.log('Service worker registration failed:', error);
} else {
  console.log('Service workers are not supported.');


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

Browser compatibilityUpdate compatibility data on GitHub

Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 40 17
Disabled From version 16: this feature is behind the Enable service workers preference.
Service workers (and Push) have been disabled in the Firefox 45 and 52 Extended Support Releases (ESR).
No 27 11.1
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support 40 40 ? 44 27 11.1 4.0

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