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ServiceWorkerContainer: 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 April 2018.
Learn more
See full compatibility
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
Note: This feature is available in Web Workers.
The message event is used in a page controlled by a service worker to receive messages from the service worker.
This event is not cancelable and does not bubble.
In this article
Syntax
Event type
Event properties
Examples
Specifications
Browser compatibility
See also
Syntax
Use the event name in methods like addEventListener(), or set an event handler property.
js
addEventListener("message", (event) => { })
onmessage = (event) => { }
Event type
A MessageEvent. Inherits from Event.
Event
MessageEvent
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
In this example the service worker get the client's ID from a fetch event and then sends it a message using Client.postMessage:
js
// service-worker.js
async function messageClient(clientId) {
const client = await clients.get(clientId);
client.postMessage("Hi client!");
}
addEventListener("fetch", (event) => {
messageClient(event.clientId);
event.respondWith(() => {
// …
});
});
The client can receive the message by listening to the message event:
js
// main.js
navigator.serviceWorker.addEventListener("message", (message) => {
console.log(message);
});
Alternatively, the client can receive the message with the onmessage event handler:
js
// main.js
navigator.serviceWorker.onmessage = (message) => {
console.log(message);
};
Specifications
Specification
Service Workers Nightly
# dom-serviceworkercontainer-onmessage
Browser compatibility
Enable JavaScript to view this browser compatibility table.
See also
Using Service Workers
Service workers basic code example
Using web workers
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This page was last modified on May 2, 2025 by MDN contributors.
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