The BroadcastChannel.onmessage event handler is a property that specifies the function to execute when a message event, of type MessageEvent, is received by this BroadcastChannel. Such an event is sent by the browser with a message broadcasted to the channel.

Note: This feature is available in Web Workers


channel.onmessage = function;


  • function is the name of a user-defined function, without the () suffix or any parameters, or an anonymous function declaration, such as function(event) {...}. An event handler always has one single parameter, containing the event, here of type MessageEvent.


bc.onmessage = function(ev) { console.log(`message event received! '${}'`); };


HTML Standard (HTML)
# handler-broadcastchannel-onmessage

Browser compatibility

BCD tables only load in the browser

See also

  • Another, more heavy weight, way of communicating between browser contexts: ServiceWorker