---
title: "Web APIs"
description: "Web-standard APIs supported by Bun for server-side JavaScript"
mode: center
---

Some Web APIs, like the [DOM API](https://developer.mozilla.org/en-US/docs/Web/API/HTML_DOM_API#html_dom_api_interfaces) and [History API](https://developer.mozilla.org/en-US/docs/Web/API/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`](https://developer.mozilla.org/en-US/docs/Web/API/fetch), [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response), [`Request`](https://developer.mozilla.org/en-US/docs/Web/API/Request), [`Headers`](https://developer.mozilla.org/en-US/docs/Web/API/Headers), [`AbortController`](https://developer.mozilla.org/en-US/docs/Web/API/AbortController), [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)                                                                                                                                                                                                                              |
| URLs                  | [`URL`](https://developer.mozilla.org/en-US/docs/Web/API/URL), [`URLSearchParams`](https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Web Workers           | [`Worker`](https://developer.mozilla.org/en-US/docs/Web/API/Worker), [`self.postMessage`](https://developer.mozilla.org/en-US/docs/Web/API/DedicatedWorkerGlobalScope/postMessage), [`structuredClone`](https://developer.mozilla.org/en-US/docs/Web/API/structuredClone), [`MessagePort`](https://developer.mozilla.org/en-US/docs/Web/API/MessagePort), [`MessageChannel`](https://developer.mozilla.org/en-US/docs/Web/API/MessageChannel), [`BroadcastChannel`](https://developer.mozilla.org/en-US/docs/Web/API/BroadcastChannel)                                                                                                                                                      |
| Streams               | [`ReadableStream`](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream), [`WritableStream`](https://developer.mozilla.org/en-US/docs/Web/API/WritableStream), [`TransformStream`](https://developer.mozilla.org/en-US/docs/Web/API/TransformStream), [`ByteLengthQueuingStrategy`](https://developer.mozilla.org/en-US/docs/Web/API/ByteLengthQueuingStrategy), [`CountQueuingStrategy`](https://developer.mozilla.org/en-US/docs/Web/API/CountQueuingStrategy) and associated classes                                                                                                                                                                                          |
| Blob                  | [`Blob`](https://developer.mozilla.org/en-US/docs/Web/API/Blob)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| WebSockets            | [`WebSocket`](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Encoding and decoding | [`Uint8Array`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array), [`Uint8Array.prototype.toBase64()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array/toBase64), [`Uint8Array.fromBase64()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array/fromBase64), [`TextEncoder`](https://developer.mozilla.org/en-US/docs/Web/API/TextEncoder), [`TextDecoder`](https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder), [`atob`](https://developer.mozilla.org/en-US/docs/Web/API/atob), [`btoa`](https://developer.mozilla.org/en-US/docs/Web/API/btoa) |
| JSON                  | [`JSON`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Timeouts              | [`setTimeout`](https://developer.mozilla.org/en-US/docs/Web/API/setTimeout), [`clearTimeout`](https://developer.mozilla.org/en-US/docs/Web/API/clearTimeout)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Intervals             | [`setInterval`](https://developer.mozilla.org/en-US/docs/Web/API/setInterval), [`clearInterval`](https://developer.mozilla.org/en-US/docs/Web/API/clearInterval)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Crypto                | [`crypto`](https://developer.mozilla.org/en-US/docs/Web/API/Crypto), [`SubtleCrypto`](https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto), [`CryptoKey`](https://developer.mozilla.org/en-US/docs/Web/API/CryptoKey)                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Debugging             | [`console`](https://developer.mozilla.org/en-US/docs/Web/API/console), [`performance`](https://developer.mozilla.org/en-US/docs/Web/API/Performance)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Microtasks            | [`queueMicrotask`](https://developer.mozilla.org/en-US/docs/Web/API/queueMicrotask)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Errors                | [`reportError`](https://developer.mozilla.org/en-US/docs/Web/API/reportError)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| User interaction      | [`alert`](https://developer.mozilla.org/en-US/docs/Web/API/Window/alert), [`confirm`](https://developer.mozilla.org/en-US/docs/Web/API/Window/confirm), [`prompt`](https://developer.mozilla.org/en-US/docs/Web/API/Window/prompt) (intended for interactive CLIs)                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Realms                | [`ShadowRealm`](https://github.com/tc39/proposal-shadowrealm)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Events                | [`EventTarget`](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget), [`Event`](https://developer.mozilla.org/en-US/docs/Web/API/Event), [`ErrorEvent`](https://developer.mozilla.org/en-US/docs/Web/API/ErrorEvent), [`CloseEvent`](https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent), [`MessageEvent`](https://developer.mozilla.org/en-US/docs/Web/API/MessageEvent)                                                                                                                                                                                                                                                                                                 |
