Web APIs

Web-standard APIs supported by Bun for server-side JavaScript

Some Web APIs, like the DOM API and History API, aren’t relevant in a server-first runtime like Bun. Many others are broadly useful outside the browser; when possible, Bun implements these Web-standard APIs instead of introducing new ones.

Bun partially or completely supports the following Web APIs.

Category	APIs
HTTP	fetch, Response, Request, Headers, AbortController, AbortSignal
URLs	URL, URLSearchParams
Web Workers	Worker, self.postMessage, structuredClone, MessagePort, MessageChannel, BroadcastChannel
Streams	ReadableStream, WritableStream, TransformStream, ByteLengthQueuingStrategy, CountQueuingStrategy and associated classes
Blob	Blob
WebSockets	WebSocket
Encoding and decoding	Uint8Array, Uint8Array.prototype.toBase64(), Uint8Array.fromBase64(), TextEncoder, TextDecoder, atob, btoa
JSON	JSON
Timeouts	setTimeout, clearTimeout
Intervals	setInterval, clearInterval
Crypto	crypto, SubtleCrypto, CryptoKey
Debugging	console, performance
Microtasks	queueMicrotask
Errors	reportError
User interaction	alert, confirm, prompt (intended for interactive CLIs)
Realms	ShadowRealm
Events	EventTarget, Event, ErrorEvent, CloseEvent, MessageEvent