ServiceWorkerGlobalScope: message event

The message event of the ServiceWorkerGlobalScope interface occurs when incoming messages are received. Controlled pages can use the ServiceWorker.postMessage() method to send messages to service workers.
The service worker can optionally send a response back via the Client.postMessage(), corresponding to the controlled page.

Bubbles No
Cancelable No
Interface ExtendableMessageEvent
Event handler property onmessage


In the below example a page gets a handle to the ServiceWorker object via, and then calls its postMessage() function.

// in the page being controlled
if (navigator.serviceWorker) {


  navigator.serviceWorker.addEventListener('message', event => {
    // event is a MessageEvent object
    console.log(`The service worker sent me a message: ${}`);

  navigator.serviceWorker.ready.then( registration => {"Hi service worker");


The service worker can receive the message by listening to the message event:

// in the service worker
addEventListener('message', event => {
  // event is an ExtendableMessageEvent object
  console.log(`The client sent me a message: ${}`);

  event.source.postMessage("Hi client");


Specification Status
Service Workers
The definition of 'message' in that specification.
Working Draft

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
message event
Chrome Full support 40Edge Full support ≤79Firefox Full support 44
Full support 44
Notes Extended Support Releases (ESR) before Firefox 78 ESR do not support service workers and the Push API.
IE No support NoOpera Full support 24Safari Full support 11.1WebView Android Full support 40Chrome Android Full support 40Firefox Android Full support 44Opera Android Full support 24Safari iOS Full support 11.3Samsung Internet Android Full support 4.0


Full support
Full support
No support
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.

See also