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WorkerGlobalScope

The WorkerGlobalScope interface of the Web Workers API is an interface representing the scope of any worker. Workers have no browsing context; this scope contains the information usually conveyed by Window objects — in this case event handlers, the console or the associated WorkerNavigator object. Each WorkerGlobalScope has its own event loop.

This interface is usually specialized by each worker type: DedicatedWorkerGlobalScope for dedicated workers, SharedWorkerGlobalScope for shared workers, and ServiceWorkerGlobalScope for ServiceWorker. The self property returns the specialized scope for each context.

Instance properties

This interface inherits properties from the EventTarget interface.

Standard properties

WorkerGlobalScope.caches Read only: Returns the CacheStorage object associated with the current context. This object enables functionality such as storing assets for offline use, and generating custom responses to requests.
WorkerGlobalScope.fonts Read only: Returns the FontFaceSet associated with the worker.
WorkerGlobalScope.indexedDB Read only: Provides a mechanism for applications to asynchronously access capabilities of indexed databases; returns an IDBFactory object.
WorkerGlobalScope.isSecureContext Read only: Returns a boolean indicating whether the current context is secure (true) or not (false).
WorkerGlobalScope.location Read only: Returns the WorkerLocation associated with the worker. It is a specific location object, mostly a subset of the Location for browsing scopes, but adapted to workers.r.
WorkerGlobalScope.navigator Read only: Returns the WorkerNavigator associated with the worker. It is a specific navigator object, mostly a subset of the Navigator for browsing scopes, but adapted to workers.
WorkerGlobalScope.origin Read only: Returns the global object's origin, serialized as a string.
WorkerGlobalScope.performance Read only: Returns the Performance associated with the worker. It is a regular performance object, except that only a subset of its property and methods are available to workers.
WorkerGlobalScope.scheduler Read only: Returns the Scheduler object associated with the current context. This is the entry point for using the Prioritized Task Scheduling API.
WorkerGlobalScope.self Read only: Returns a reference to the WorkerGlobalScope itself. Most of the time it is a specific scope like DedicatedWorkerGlobalScope, SharedWorkerGlobalScope or ServiceWorkerGlobalScope.

Non-standard properties

console Read only Non-standard: Returns the console associated with the worker.

Instance methods

This interface inherits methods from the EventTarget interface.

Standard methods

WorkerGlobalScope.atob(): Decodes a string of data which has been encoded using base-64 encoding.
WorkerGlobalScope.btoa(): Creates a base-64 encoded ASCII string from a string of binary data.
WorkerGlobalScope.clearInterval(): Cancels the repeated execution set using setInterval().
WorkerGlobalScope.clearTimeout(): Cancels the delayed execution set using setTimeout().
WorkerGlobalScope.createImageBitmap(): Accepts a variety of different image sources, and returns a Promise which resolves to an ImageBitmap. Optionally the source is cropped to the rectangle of pixels originating at (sx, sy) with width sw, and height sh.
WorkerGlobalScope.fetch(): Starts the process of fetching a resource from the network.
WorkerGlobalScope.importScripts(): Imports one or more scripts into the worker's scope. You can specify as many as you'd like, separated by commas. For example: importScripts('foo.js', 'bar.js');
WorkerGlobalScope.setInterval(): Schedules a function to execute every time a given number of milliseconds elapses.
WorkerGlobalScope.setTimeout(): Schedules a function to execute in a given amount of time.
WorkerGlobalScope.reportError(): Reports an error in a script, emulating an unhandled exception.

Non-standard methods

WorkerGlobalScope.dump() Deprecated Non-standard: Allows you to write a message to stdout — i.e. in your terminal. This is the same as Firefox's window.dump, but for workers.

Events

error: Fires when an error occurred.
offline: Fires when the browser has lost access to the network and the value of navigator.onLine switched to false.
online: Fires when the browser has gained access to the network and the value of navigator.onLine switched to true.
languagechange: Fires at the global/worker scope object when the user's preferred languages change.
rejectionhandled Non-standard: Fires on handled Promise rejection events.
unhandledrejection Non-standard: Fires on unhandled Promise rejection events.

Example

You won't access WorkerGlobalScope directly in your code; however, its properties and methods are inherited by more specific global scopes such as DedicatedWorkerGlobalScope and SharedWorkerGlobalScope. For example, you could import another script into the worker and print out the contents of the worker scope's navigator object using the following two lines:

importScripts("foo.js");
console.log(navigator);

Note: Since the global scope of the worker script is effectively the global scope of the worker you are running (DedicatedWorkerGlobalScope or whatever) and all worker global scopes inherit methods, properties, etc. from WorkerGlobalScope, you can run lines such as those above without specifying a parent object.

Specifications

Specification
HTML Standard # the-workerglobalscope-common-interface

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`WorkerGlobalScope`	4	12	3.5	10	10.6	4	4.4	18	4	11	5	1.0
`dump`	No	No	3.5 This method exists but has no effect.	No	No	No	No	No	4 This method exists but has no effect.	No	No	No
`error_event`	4	12	3.5	10	11.5	4	4.4	18	4	14	5	1.0
`fonts`	69	79	105	No	56	15	69	69	105	48	15	10.0
`importScripts`	4	12	4	10	10.6	4	4.4	18	4	11	5	1.0
`languagechange_event`	4	79	74	No	11.5	4	≤37	18	79	14	5	1.0
`location`	4	12	3.5	10	11.5	4	4.4	18	4	14	5	1.0
`navigator`	4	17	3.5	10	11.5	4	4.4	18	4	14	5	1.0
`offline_event`	No	No	29	No	No	8	No	No	29	No	8	No
`online_event`	No	No	29	No	No	8	No	No	29	No	8	No
`securitypolicyviolation_event`	41	15	63	No	28	10	41	41	63	28	10	4.0
`self`	4	12	3.5	10	11.5	4	4.4	18	34	14	5	1.0