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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

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