WorkerGlobalScope

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.

* Some parts of this feature may have varying levels of support.

Note: This feature is only available inWeb Workers.

TheWorkerGlobalScope interface of theWeb Workers API is an interface representing the scope of any worker. Workers have no browsing context; this scope contains the information usually conveyed byWindow objects — in this case event handlers, the console or the associatedWorkerNavigator object. EachWorkerGlobalScope has its own event loop.

This interface is usually specialized by each worker type:DedicatedWorkerGlobalScope for dedicated workers,SharedWorkerGlobalScope for shared workers, andServiceWorkerGlobalScope forServiceWorker. Theself property returns the specialized scope for each context.

Instance properties

This interface inherits properties from theEventTarget interface.

WorkerGlobalScope.cachesRead onlySecure context: Returns theCacheStorage object associated with the current context. This object enables functionality such as storing assets for offline use, and generating custom responses to requests.
WorkerGlobalScope.crossOriginIsolatedRead only: Returns a boolean value that indicates whether the website is in a cross-origin isolation state.
WorkerGlobalScope.cryptoRead only: Returns theCrypto object associated to the global object.
WorkerGlobalScope.fontsRead only: Returns theFontFaceSet associated with the worker.
WorkerGlobalScope.indexedDBRead only: Provides a mechanism for workers to asynchronously access capabilities of indexed databases; returns anIDBFactory object.
WorkerGlobalScope.isSecureContextRead only: Returns a boolean indicating whether the current context is secure (true) or not (false).
WorkerGlobalScope.locationRead only: Returns theWorkerLocation associated with the worker. It is a specific location object, mostly a subset of theLocation for browsing scopes, but adapted to workers.
WorkerGlobalScope.navigatorRead only: Returns theWorkerNavigator associated with the worker. It is a specific navigator object, mostly a subset of theNavigator for browsing scopes, but adapted to workers.
WorkerGlobalScope.originRead only: Returns the global object's origin, serialized as a string.
WorkerGlobalScope.performanceRead only: Returns thePerformance associated with the worker. Only a subset of the properties and methods of thePerformance interface are available to workers.
WorkerGlobalScope.schedulerRead only: Returns theScheduler object associated with the current context. This is the entry point for using thePrioritized Task Scheduling API.
WorkerGlobalScope.trustedTypesRead only: Returns theTrustedTypePolicyFactory object associated with the global object, providing the entry point for using theTrusted Types API.
WorkerGlobalScope.selfRead only: Returns a reference to theWorkerGlobalScope itself. Most of the time it is a specific scope likeDedicatedWorkerGlobalScope,SharedWorkerGlobalScope orServiceWorkerGlobalScope.

Instance methods

This interface inherits methods from theEventTarget interface.

WorkerGlobalScope.atob(): Decodes a string of data which has been encoded using base-64 encoding.
WorkerGlobalScope.btoa(): Creates a base-64 encodedASCII string from a string of binary data.
WorkerGlobalScope.clearInterval(): Cancels the repeated execution set usingWorkerGlobalScope.setInterval().
WorkerGlobalScope.clearTimeout(): Cancels the delayed execution set usingWorkerGlobalScope.setTimeout().
WorkerGlobalScope.createImageBitmap(): Accepts a variety of different image sources, and returns aPromise which resolves to anImageBitmap. Optionally the source is cropped to the rectangle of pixels originating at(sx, sy) with width sw, and height sh.
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.
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.queueMicrotask(): Queues a microtask to be executed at a safe time prior to control returning to the browser's event loop.
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.structuredClone(): Creates adeep clone of a given value using thestructured clone algorithm.
WorkerGlobalScope.reportError(): Reports an error in a script, emulating an unhandled exception.

Events

error: Fired when an error occurred.
languagechange: Fired at the global/worker scope object when the user's preferred languages change.
offline: Fired when the browser has lost access to the network and the value ofnavigator.onLine switched tofalse.
online: Fired when the browser has gained access to the network and the value ofnavigator.onLine switched totrue.
rejectionhandled: Fired on handledPromise rejection events.
securitypolicyviolation: Fired when aContent Security Policy is violated.
unhandledrejection: Fired on unhandledPromise rejection events.

Example

You won't accessWorkerGlobalScope directly in your code; however, its properties and methods are inherited by more specific global scopes such asDedicatedWorkerGlobalScope andSharedWorkerGlobalScope. For example, you could import another script into the worker and print out the contents of the worker scope'snavigator 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. fromWorkerGlobalScope, you can run lines such as those above without specifying a parent object.