The onmessage property of the ServiceWorkerGlobalScope interface is an event handler fired whenever a message event occurs — when incoming messages are received.

Note: Service workers define the extendable event to allow extending the lifetime of the event. For the message event, service workers use the ExtendableMessageEvent interface which extends the ExtendableEvent interface.

Note: Messages received from service worker contexts (e.g. as the event object of onmessage) are represented by MessageEvent objects in modern browsers, for consistency with other web messaging features. (They used to be represented by ServiceWorkerMessageEvent objects, which have now been deprecated.)


serviceWorkerGlobalScope.onmessage = function(extendableMessageEvent) { ... };


self.addEventListener('message', function(messageEvent) {
  console.log('Handling message event:', messageEvent);


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

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
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.