Web APIs

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. The following Web APIs are partially or completely supported.

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`

Get Started

Core Runtime

File & Module System

HTTP server

Networking

Data & Storage

Concurrency

Process & System

Interop & Tooling

Utilities

Standards & Compatibility

Contributing