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

The Clients interface provides access to Client objects. Access it via self.clients within a service worker.


Returns a Promise for a Client matching a given id.
Returns a Promise for an array of Client objects. An options argument allows you to control the types of clients returned. 
Opens a new browser window for a given url and returns a Promise for the new WindowClient.
Allows an active service worker to set itself as the controller for all clients within its scope


The following example shows an existing chat window or creates a new one when the user clicks a notification.

addEventListener('notificationclick', event => {
  event.waitUntil(async function() {
    const allClients = await clients.matchAll({
      includeUncontrolled: true

    let chatClient;

    // Let's see if we already have a chat window open:
    for (const client of allClients) {
      const url = new URL(client.url);

      if (url.pathname == '/chat/') {
        // Excellent, let's use it!
        chatClient = client;

    // If we didn't find an existing chat window,
    // open a new one:
    if (!chatClient) {
      chatClient = await clients.openWindow('/chat/');

    // Message the client:
    chatClient.postMessage("New chat messages!");


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

Browser compatibility

BCD tables only load in the browser

See also