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    The Worker() constructor creates a Worker object that executes the script at the specified URL. This script must obey the same-origin policy.

    If the URL has an invalid syntax or if the same-origin policy is violated a DOMException of type SECURITY_ERR is thrown.

    Note: that there is a disagreement among browser manufacturers about whether a data URI is of the same origin or not. Though Gecko 10.0 (Firefox 10.0 / Thunderbird 10.0 / SeaMonkey 2.7) and later accept data URIs, that's not the case in all other browsers.


    var myWorker = new Worker("aURL");


    Is a DOMString representing the URL of the script the worker will execute. It must obey the same-origin policy.


    The following code snippet shows creation of a Worker object using the Worker() constructor and subsequent usage of the object:

    var myWorker = new Worker("worker.js");
    first.onchange = function() {
      console.log('Message posted to worker');

    For a full example, see ourBasic dedicated worker example (run dedicated worker).


    Specification Status Comment
    WHATWG HTML Living Standard
    The definition of 'Worker()' in that specification.
    Living Standard No change from Web Workers.
    Web Workers
    The definition of 'Worker()' in that specification.
    Recommendation Initial definition.

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
    Basic support 4 3.5 10.0 10.6 4
    Feature Android Firefox Mobile (Gecko) Firefox OS (Gecko) IE Phone Opera Mobile Safari Mobile
    Basic support 4.4 3.5 1.0.1 10.0 11.5 5.1

    See also

    The Worker interface it belongs to.

    Document Tags and Contributors

    Contributors to this page: kscarfone, chrisdavidmills, teoli
    Last updated by: teoli,