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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 type read-only property of the Client interface indicates the type of client the service worker is controlling.


var myClientType = Client.type;


A string, representing the client type. The value can be one of

  • window
  • worker
  • sharedworker
  • all


// service worker client (e.g. a document)
function sendMessage(message) {
  return new Promise(function(resolve, reject) {
    // note that this is the ServiceWorker.postMessage version
    window.serviceWorker.onMessage = function(e) {

// controlling service worker
self.addEventListener("message", function(e) {
  // e.source is a client object
  e.source.postMessage("Hello! Your message was: " +;
  // Let's also post the type value back to the client


Specification Status Comment
Service Workers
The definition of 'type' in that specification.
Editor's Draft Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 60 54.0 (54.0) No support 47 No support
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support No support 54.0 (54.0) No support 47 No support ?

Document Tags and Contributors

 Contributors to this page: jan.roudaut, chrisdavidmills
 Last updated by: jan.roudaut,