The SharedWorker interface represents a specific kind of worker that can be accessed from several browsing contexts, such as several windows, iframes or even workers. They implement an interface different than dedicated workers and have a different global scope, SharedWorkerGlobalScope.

Note: If SharedWorker can be accessed from several browsing contexts, all those browsing contexts must share the exact same origin (same protocol, host and port).

Constructors

SharedWorker()
Creates a shared web worker that executes the script at the specified URL.

Properties

Inherits properties from its parent, EventTarget, and implements properties from AbstractWorker.

AbstractWorker.onerror
Is an EventListener that is called whenever an ErrorEvent of type error bubbles through the worker.
SharedWorker.port Read only
Returns a MessagePort object used to communicate and control the shared worker.

Methods

Inherits methods from its parent, EventTarget, and implements methods from AbstractWorker.

Example

In our Basic shared worker example (run shared worker), we have two HTML pages, each of which uses some JavaScript to perform a simple calculation. The different scripts are using the same worker file to perform the calculation — they can both access it, even if their pages are running inside different windows.

The following code snippet shows creation of a SharedWorker object using the SharedWorker() constructor. Both scripts contain this:

var myWorker = new SharedWorker('worker.js');

Both scripts then access the worker through a MessagePort object created using the SharedWorker.port property. If the onmessage event is attached using addEventListener, the port is manually started using its start() method:

myWorker.port.start();

When the port is started, both scripts post messages to the worker and handle messages sent from it using port.postMessage() and port.onmessage, respectively:

first.onchange = function() {
  myWorker.port.postMessage([first.value,second.value]);
  console.log('Message posted to worker');
}

second.onchange = function() {
  myWorker.port.postMessage([first.value,second.value]);
  console.log('Message posted to worker');
}

myWorker.port.onmessage = function(e) {
  result1.textContent = e.data;
  console.log('Message received from worker');
}

Inside the worker we use the SharedWorkerGlobalScope.onconnect handler to connect to the same port discussed above. The ports associated with that worker are accessible in the connect event's ports property — we then use MessagePort start() method to start the port, and the onmessage handler to deal with messages sent from the main threads.

onconnect = function(e) {
  var port = e.ports[0];

  port.addEventListener('message', function(e) {
    var workerResult = 'Result: ' + (e.data[0] * e.data[1]);
    port.postMessage(workerResult);
  });

  port.start(); // Required when using addEventListener. Otherwise called implicitly by onmessage setter.
}

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'SharedWorker' in that specification.
Living Standard No change from Unknown.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic supportChrome Full support 4Edge ? Firefox Full support 29IE Full support 10Opera Full support 10.6Safari No support 5 — 6.1WebView Android Full support YesChrome Android Full support YesEdge Mobile ? Firefox Android Full support 33Opera Android Full support 11.5Safari iOS No support 5.1 — 7.1Samsung Internet Android Full support Yes
SharedWorker() constructorChrome Full support 4Edge ? Firefox Full support 29IE Full support 10Opera Full support 10.6Safari No support 5 — 6.1WebView Android Full support YesChrome Android Full support YesEdge Mobile ? Firefox Android Full support 33Opera Android Full support 11.5Safari iOS No support 5.1 — 7.1Samsung Internet Android Full support Yes
portChrome Full support 4Edge ? Firefox Full support 29IE Full support 10Opera Full support 10.6Safari No support 5 — 6.1WebView Android Full support YesChrome Android Full support YesEdge Mobile ? Firefox Android Full support 33Opera Android Full support 11.5Safari iOS No support 5.1 — 7.1Samsung Internet Android Full support Yes

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown

See also

Document Tags and Contributors

Last updated by: antigone2,