In addition to the standard JavaScript set of functions (such as String, Array, Object, JSON, etc.), there are a variety of functions available from the DOM to workers. This article provides a list of those.

Workers run in a different global context than the current window! While Window is not directly available to workers, many of the same methods are defined in a shared mixin (WindowOrWorkerGlobalScope), and made available to workers through their own WorkerGlobalScope-derived contexts:

• DedicatedWorkerGlobalScope for dedicated workers
• SharedWorkerGlobalScope for shared workers
• ServiceWorkerGlobalScope for service workers

Some of the functions (a subset) that are common to all workers and to the main thread (from WindowOrWorkerGlobalScope) are:

• atob()
• btoa()
• clearInterval()
• clearTimeout()
• dump() Non-standard
• queueMicrotask()
• setInterval()
• setTimeout()
• structuredClone()
• window.requestAnimationFrame (dedicated workers only)
• window.cancelAnimationFrame (dedicated workers only)

The following functions are only available to workers:

• WorkerGlobalScope.importScripts() (all workers)
• DedicatedWorkerGlobalScope.postMessage (dedicated workers only)

The following Web APIs are available to workers:

• Barcode Detection API
• Broadcast Channel API
• Cache API
• Channel Messaging API
• Console API
• Web Crypto API (e.g. Crypto)
• CSS Font Loading API
• CustomEvent
• Encoding API (e.g. TextEncoder, TextDecoder)
• Fetch API
• FileReader
• FileReaderSync (only works in workers!)
• FormData
• ImageBitmap
• ImageData
• IndexedDB
• Media Source Extensions API (dedicated workers only)
• Network Information API
• Notifications API
• OffscreenCanvas (and all the canvas context APIs)
• Performance API, including:
  • Performance
  • PerformanceEntry
  • PerformanceMeasure
  • PerformanceMark
  • PerformanceObserver
  • PerformanceResourceTiming
• Server-sent events
• ServiceWorkerRegistration
• URL API (e.g. URL)
• WebCodecs_API
• WebSocket
• XMLHttpRequest

Workers can also spawn other workers, so these APIs are also available:

• Worker
• WorkerGlobalScope
• WorkerLocation
• WorkerNavigator

• Using web workers
• Worker