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 openWindow() method of the Clients interface creates a new top level browsing context and loads a given URL. If the calling script doesn't have permission to show popups, openWindow() will throw an InvalidAccessError.

In Firefox, the method is allowed to show popups only when called as the result of a notification click event.

In Chrome for Android, the method may instead open the URL in an existing browsing context provided by a standalone web app previously added to the user's home screen.


ServiceWorkerClients.openWindow(url).then(function(WindowClient) {
  // do something with your WindowClient


A USVString representing the URL of the client you want to open in the window. Generally this value must be a URL from the same origin as the calling script.

Return value

Promise that resolves to a WindowClient object if the URL is from the same origin as the service worker or a null value otherwise.


// When the user clicks a notification focus the window if it exists or open
// a new one otherwise.
onotificationclick = function(event) {
  var found = false;
  clients.matchAll().then(function(clients) {
    for (i = 0; i < clients.length; i++) {
      if (clients[i].url === {
        // We already have a window to use, focus it.
        found = true;
    if (!found) {
      // Create a new window.
      clients.openWindow( {
        // do something with the windowClient.


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 42.0[1] 45.0 (45.0)[2] No support ? 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 45.0 (45.0) (Yes) No support ? No support 40.0 [1][3]
  • [1] In Chrome 43 and later, you can open any URL. In Chrome 42 you could only open URLs on the same origin.
  • [2] Service workers (and Push) have been disabled in the Firefox 45 Extended Support Release (ESR.)
  • [3] In Chrome for Android 51 and later, URLs may open inside an existing browsing context provided by a standalone web app.

Document Tags and Contributors

 Last updated by: samthor,