Window: message event

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The message event is fired on a Window object when the window receives a message, for example from a call to Window.postMessage() from another browsing context.

This event is not cancellable and does not bubble.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

js
addEventListener("message", (event) => {});

onmessage = (event) => {};

Event type

Event properties

This interface also inherits properties from its parent, Event.

MessageEvent.data Read only

The data sent by the message emitter.

MessageEvent.origin Read only

A string representing the origin of the message emitter.

MessageEvent.lastEventId Read only

A string representing a unique ID for the event.

MessageEvent.source Read only

A MessageEventSource (which can be a WindowProxy, MessagePort, or ServiceWorker object) representing the message emitter.

MessageEvent.ports Read only

An array of MessagePort objects representing the ports associated with the channel the message is being sent through (where appropriate, e.g. in channel messaging or when sending a message to a shared worker).

Examples

Suppose a script sends a message to a different browsing context, such as another <iframe>, using code like this:

js
const targetFrame = window.top.frames[1];
const targetOrigin = "https://example.org";
const windowMessageButton = document.querySelector("#window-message");

windowMessageButton.addEventListener("click", () => {
  targetFrame.postMessage("hello there", targetOrigin);
});

The receiver can listen for the message using addEventListener() with code like this:

js
window.addEventListener("message", (event) => {
  console.log(`Received message: ${event.data}`);
});

Alternatively the listener could use the onmessage event handler property:

js
window.onmessage = (event) => {
  console.log(`Received message: ${event.data}`);
};

Specifications

Specification
HTML
# event-message
HTML
# handler-window-onmessage

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
message event

Legend

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Full support
Full support

See also