Runtime Standards & Compatibility
Web APIs
Web-standard APIs supported by Bun for server-side JavaScript
Some Web APIs aren't relevant in the context of a server-first runtime like Bun, such as the DOM API or History API. Many others, though, are broadly useful outside of the browser context; when possible, Bun implements these Web-standard APIs instead of introducing new APIs.
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 | atob, btoa, TextEncoder, TextDecoder |
| 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 |