ServiceWorkerContainer: register() method

scriptURL

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 string 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 (by resolving ./ against scriptURL). See the Examples section for more information on how it works.

type

A string specifying the type of worker to create. Valid values are:

'classic'

The loaded service worker is in a standard script. This is the default.

'module'

The loaded service worker is in an ES module and the import statement is available on worker contexts. For ES module compatibility info, see the browser compatibility data table for the ServiceWorker interface.

updateViaCache

A string indicating how the HTTP cache is used for service worker scripts resources during updates. Note: This only refers to the service worker script and its imports, not other resources fetched by these scripts.

'all'

The HTTP cache will be queried for the main script, and all imported scripts. If no fresh entry is found in the HTTP cache, then the scripts are fetched from the network.

'imports'

The HTTP cache will be queried for imports, but the main script will always be updated from the network. If no fresh entry is found in the HTTP cache for the imports, they're fetched from the network.

'none'

The HTTP cache will not be used for the main script or its imports. All service worker script resources will be updated from the network.

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). Suppose the service worker code is at example.com/sw.js, and the registration code at example.com/index.html. The service worker code 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(
    (registration) => {
      console.log("Service worker registration succeeded:", registration);
    },
    (error) => {
      console.error(`Service worker registration failed: ${error}`);
    },
  );
} else {
  console.error("Service workers are not supported.");
}

The following code, with all code in the same place, would apply to exactly the same pages as the example above. Alternatively, if the service worker code is at example.com/product/sw.js, and the registration code at example.com/product/description.html. then the service worker would only apply to resources under example.com/product. Remember the scope, when included, uses the page's location as its base.

if ("serviceWorker" in navigator) {
  // declaring scope manually
  navigator.serviceWorker.register("./sw.js", { scope: "./" }).then(
    (registration) => {
      console.log("Service worker registration succeeded:", registration);
    },
    (error) => {
      console.error(`Service worker registration failed: ${error}`);
    },
  );
} else {
  console.error("Service workers are not supported.");
}

There is frequent confusion surrounding the meaning and use of scope. A service worker can't have a scope broader than its own location, unless the server specifies a broader maximum scope in a Service-Worker-Allowed header on the service worker script. Therefore you should use the scope option when you need a narrower scope than the default.

The following code, if included in example.com/index.html, at the root of a site, would only apply to resources under example.com/product.

if ("serviceWorker" in navigator) {
  // declaring scope manually
  navigator.serviceWorker.register("./sw.js", { scope: "/product/" }).then(
    (registration) => {
      console.log("Service worker registration succeeded:", registration);
    },
    (error) => {
      console.error(`Service worker registration failed: ${error}`);
    },
  );
} else {
  console.error("Service workers are not supported.");
}

As noted above, servers can change the default maximum scope by setting the Service-Worker-Allowed header on the service worker script. In this case, the scope option should specify a scope narrower than the header value, but potentially larger than the service worker's location.

The following code, if included in example.com/product/index.html, would apply to all resources under example.com if the server set the Service-Worker-Allowed header to / or https://example.com/ when serving sw.js. If the server doesn't set the header, the service worker registration will fail, as the requested scope is too broad.

if ("serviceWorker" in navigator) {
  // Declaring a broadened scope
  navigator.serviceWorker.register("./sw.js", { scope: "/" }).then(
    (registration) => {
      // The registration succeeded because the Service-Worker-Allowed header
      // had set a broadened maximum scope for the service worker script
      console.log("Service worker registration succeeded:", registration);
    },
    (error) => {
      // This happens if the Service-Worker-Allowed header doesn't broaden the scope
      console.error(`Service worker registration failed: ${error}`);
    },
  );
} else {
  console.error("Service workers are not supported.");
}

• ServiceWorkerRegistration: unregister() method
• Service worker API
• Using service workers