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Bun — A fast all-in-one JavaScript runtime 
Bun is a fast JavaScript
Bun is joining Anthropic & Anthropic is betting on Bun →
Bun v1.3.7
50% faster `Buffer.from(array)`, 35% faster async/await, 3x faster `array.flat()`, 90% faster `padStart`/`padEnd` via JSC upgrade. New: `Bun.JSO...
Bun v1.3.6
Bun.Archive API for creating & extracting tarballs with gzip compression, Bun.JSONC for parsing JSON with comments, metafile & files options in ...
Bun v1.3.5
Bun.Terminal API, compile-time feature flags, improved Bun.stringWidth accuracy, V8 C++ value type checking APIs, Content-Disposition support fo...
Bun v1.3.4
URLPattern API, Fake Timers for bun:test, Custom Proxy Headers in fetch(),console.log %j format, http.Agent connection pooling fix, Standalone e...
Bun v1.3.3
CompressionStream and DecompressionStream, Control .env and bunfig.toml loading in standalone executables, `retry` and `repeats` in `bun:test`, ...
Bun v1.3.2
Hoisted installs restored as default for backward compatibility. CPU profiling with --cpu-prof, faster installs for packages with post-install s...
Bun v1.3.7 is here! →
Bun is a fast JavaScript
all-in-one toolkit|
Bun is a fast, incrementally adoptable all-in-one JavaScript, TypeScript & JSX toolkit. Use individual tools like bun test or bun install in Node.js projects, or adopt the complete stack with a fast JavaScript runtime, bundler, test runner, and package manager built in. Bun aims for 100% Node.js compatibility.
Install Bun v1.3.7
curl -fsSL https://bun.sh/install | bashpowershell -c "irm bun.sh/install.ps1 | iex"USED BY
Bundling 10,000 React components
Build time in milliseconds (Linux x64, Hetzner)
Bun
v1.3.0
269.1 ms
Rolldown
v1.0.0-beta.42
494.9 ms
esbuild
v0.25.10
571.9 ms
Farm
v1.0.5
1,608 ms
Rspack
v1.5.8
2,137 ms
Express.js 'hello world'
HTTP requests per second (Linux x64)
- bun: 59,026 requests per second59,026
- deno: 25,335 requests per second25,335
- node: 19,039 requests per second19,039
WebSocket chat server
Messages sent per second (Linux x64, 32 clients)
- bun: 2,536,227 messages sent per second2,536,227
- deno: 1,320,525 messages sent per second1,320,525
- node: 435,099 messages sent per second435,099
Load a huge table
Queries per second. 100 rows x 100 parallel queries
- bun: 28,571 queries per second28,571
- node: 14,522 queries per second14,522
- deno: 11,169 queries per second11,169
Four tools, one toolkit
Use them together as an all-in-one toolkit, or adopt them incrementally. bun test works in Node.js projects. bun install can be used as the fastest npm client. Each tool stands on its own.
Test Runner
Replaces Jest & VitestJest-compatible test runner with built-in code coverage and watch mode
$ bun test- ✓Jest-compatible expect() API
- ✓Snapshot testing
- ✓Watch mode & lifecycle hooks
- ✓DOM APIs via happy-dom
- ✓Concurrent test execution
- ✓Built-in code coverage
Who uses Bun?
Claude Code uses Bun
Bun's single file executables & fast start times are great for CLIs.
Railway Functions powered by Bun
Bun's all-in-one toolkit makes Railway's serverless functions fast and easy to use.
Midjourney uses Bun
Bun's built-in WebSocket server helps Midjourney publish image generation notifications at scale.
What's different about Bun?
Bun provides extensive builtin APIs and tooling
Everything you need to build & ship
Production-ready APIs and tools, built into Bun
HTTP & WebSockets
Databases
File System
Testing
Build & Deploy
TypeScript & DX
Security
System Integration
$ bun run
Bun is a JavaScript runtime.
Bun is a new JavaScript runtime built from scratch to serve the modern JavaScript ecosystem. It has three major design goals:
- Speed. Bun starts fast and runs fast. It extends JavaScriptCore, the performance-minded JS engine built for Safari. Fast start times mean fast apps and fast APIs.
- Elegant APIs. Bun provides a minimal set of highly-optimized APIs for performing common tasks, like starting an HTTP server and writing files.
- Cohesive DX. Bun is a complete toolkit for building JavaScript apps, including a package manager, test runner, and bundler.
Bun is designed as a drop-in replacement for Node.js. It natively implements thousands of Node.js and Web APIs, including fs, path, Buffer and more.
The goal of Bun is to run most of the world's server-side JavaScript and provide tools to improve performance, reduce complexity, and multiply developer productivity.
Bun works with Next.js
Lee Robinson
VP of Developer Experience at Cursor (Anysphere)
app/blog/[slug]/page.tsx
import { s3, $, sql } from "bun";
export default async function BlogPage({ params }) {
const [post] = await sql`
SELECT title, image_key, content
FROM posts
WHERE slug = ${params.slug}
`;
const imgUrl = s3.file(post.image_key).presign({•••expiresIn: 3600 });
const wordCount = await $`echo ${post.content} | wc -w`;
return (
<div>
<h1>{post.title}</h1>
<img src={imgUrl} />
<p>Word count: {wordCount}</p>
</div>
);
}
Full speed full-stack
Fast frontend apps with Bun's built-in high performance development server and production bundler. You've never seen hot-reloading this fast!
Develop and ship frontend apps
Bun's built-in bundler and dev server make frontend development fast and simple. Develop with instant hot reload, then ship optimized production builds—all with zero configuration.
$ bun init --react
Start a dev server
Run bun ./index.html to start a dev server. TypeScript, JSX, React, and CSS imports work out of the box.
Hot Module Replacement
Built-in HMR preserves application state during development. Changes appear instantly—no manual refresh needed.
Build for production
Build optimized bundles with bun build ./index.html --production. Tree-shaking, minification, and code splitting work out of the box.
$ bun install
Bun is an npm-compatible package manager.
Bun
pnpm
17x slower
npm
29x slower
Yarn
33x slower
Installing dependencies from cache for a Remix app.
View benchmark
$ bun test
Bun is a test runner that makes the rest look like test walkers.
Bun
Vitest
5x slower
Jest+SWC
8x slower
Jest+tsjest
18x slower
Jest+Babel
20x slower
The APIs you need. Baked in.
Start an HTTP server
Start a WebSocket server
Read and write files
Hash a password
Frontend dev server
Write a test
Query PostgreSQL
Use Redis
Import YAML
Set cookies
Run a shell script
Call a C function
index.tsx
import { sql, serve } from "bun";
const server = serve({
port: 3000,
routes: {
"/": new Response("Welcome to Bun!"),
"/api/users": async (req) => {
const users = await sql`SELECT * FROM users LIMIT 10`;
return Response.json({ users });
},
},
});
console.log(`Listening on localhost:${server.port}`);index.tsx
const server = Bun.serve<{ authToken: string; }>({
fetch(req, server) {
// use a library to parse cookies
const cookies = parseCookies(req.headers.get("Cookie"));
server.upgrade(req, {
data: { authToken: cookies['X-Token'] },
});
},
websocket: {
// handler called when a message is received
async message(ws, message) {
console.log(`Received: ${message}`);
const user = getUserFromToken(ws.data.authToken);
await db.Message.insert({
message: String(message),
userId: user.id,
});
},
},
});
console.log(`Listening on localhost:${server.port}`);index.tsx
const file = Bun.file(import.meta.dir + '/package.json'); // BunFile
const pkg = await file.json(); // BunFile extends Blob
pkg.name = 'my-package';
pkg.version = '1.0.0';
await Bun.write(file, JSON.stringify(pkg, null, 2));
index.tsx
const password = "super-secure-pa$$word";
const hash = await Bun.password.hash(password);
// => $argon2id$v=19$m=65536,t=2,p=1$tFq+9AVr1bfPxQdh...
const isMatch = await Bun.password.verify(password, hash);
// => trueserver.ts
// Run 'bun init --react' to get started
import { serve } from "bun";
import reactApp from "./index.html";
serve({
port: 3000,
routes: {
"/": reactApp,
"/api/hello": () => Response.json({ message: "Hello!" }),
},
development: {
console: true, // Stream browser logs to terminal
hmr: true, // Enable hot module reloading
},
});index.test.tsx
import { test, expect } from "bun:test";
// Run tests concurrently for better performance
test.concurrent("fetch user 1", async () => {
const res = await fetch("https://api.example.com/users/1");
expect(res.status).toBe(200);
});
test.concurrent("fetch user 2", async () => {
const res = await fetch("https://api.example.com/users/2");
expect(res.status).toBe(200);
});
test("addition", () => {
expect(2 + 2).toBe(4);
});
index.tsx
import { sql } from "bun";
// Query with automatic SQL injection prevention
const users = await sql`
SELECT * FROM users
WHERE active = ${true}
LIMIT 10
`;
// Insert with object notation
const [user] = await sql`
INSERT INTO users ${sql({
name: "Alice",
email: "alice@example.com"
})}
RETURNING *
`;config.yaml
// Import YAML files directly
import config from "./config.yaml";
console.log(config.database.host);
// => "localhost"
// Or parse YAML at runtime
const data = Bun.YAML.parse(`
name: my-app
version: 1.0.0
database:
host: localhost
port: 5432
`);index.tsx
import { serve } from "bun";
serve({
port: 3000,
routes: {
"/": (request) => {
// Read cookies with built-in parsing
const sessionId = request.cookies.get("session_id");
// Set cookies
request.cookies.set("session_id", "abc123", {
path: "/",
httpOnly: true,
secure: true,
});
return Response.json({ success: true });
},
},
});index.tsx
import { redis } from "bun";
// Set a key
await redis.set("greeting", "Hello from Bun!");
console.log(db.query("SELECT 1 as x").get());
// { x: 1 }
index.tsx
import { $ } from 'bun';
// Run a shell command (also works on Windows!)
await $`echo "Hello, world!"`;
const response = await fetch("https://example.com");
// Pipe the response body to gzip
const data = await $`gzip < ${response}`.arrayBuffer();index.tsx
import { dlopen, FFIType, suffix } from "bun:ffi";
// `suffix` is either "dylib", "so", or "dll" depending on the platform
const path = `libsqlite3.${suffix}`;
const {
symbols: {
sqlite3_libversion, // the function to call
},
} = dlopen(path, {
sqlite3_libversion: {
args: [], // no arguments
returns: FFIType.cstring, // returns a string
},
});
console.log(`SQLite 3 version: ${sqlite3_libversion()}`);Learn more
Developers love Bun.
Sainder
Jan 17
@Sainder_Pradipt
Bun
Lic
Jan 18
@Lik228
bun
Martin Navrátil
Jan 17
@martin_nav_
Bun....
SaltyAom
Jan 17
@saltyAom
bun
reaxios
Jan 17
@reaxios
bun install bun
kyge
Jan 17
@0xkyge
bun
James Landrum
Jan 17
@JamesRLandrum
Node
orlowdev
Jan 17
@orlowdev
Yeah, bun, but my code does not have dependencies.
hola
Jan 17
@jdggggyujhbc
bun
std::venom
Jan 17
@std_venom
Bun
tiago
Jan 19
@tiagorangel23
should have used Bun instead of npm
Sainder
Jan 17
@Sainder_Pradipt
Bun
Lic
Jan 18
@Lik228
bun
Martin Navrátil
Jan 17
@martin_nav_
Bun....
SaltyAom
Jan 17
@saltyAom
bun
reaxios
Jan 17
@reaxios
bun install bun
kyge
Jan 17
@0xkyge
bun
James Landrum
Jan 17
@JamesRLandrum
Node
orlowdev
Jan 17
@orlowdev
Yeah, bun, but my code does not have dependencies.
hola
Jan 17
@jdggggyujhbc
bun
std::venom
Jan 17
@std_venom
Bun
tiago
Jan 19
@tiagorangel23
should have used Bun instead of npm
46officials
Jan 19
@46officials
Bun
yuki
Jan 19
@staticdots
Bun
Stefan
Jan 17
@stefangarofalo
Bun
Samuel
Jan 17
@samueldans0
Bun always
Divin Prince
Jan 17
@divinprnc
Yeah Bun
Gibson
Jan 16
@GibsonSMurray
bun
Oggie Sutrisna
Jan 16
@oggiesutrisna
bun
emanon
Jan 16
@0x_emanon
✅ bun
yuki
Jan 16
@staticdots
bun
SpiritBear
Jan 16
@0xSpiritBear
bun
Ayu
Jan 12
@Ayuu2809
Bun good 🧅
46officials
Jan 19
@46officials
Bun
yuki
Jan 19
@staticdots
Bun
Stefan
Jan 17
@stefangarofalo
Bun
Samuel
Jan 17
@samueldans0
Bun always
Divin Prince
Jan 17
@divinprnc
Yeah Bun
Gibson
Jan 16
@GibsonSMurray
bun
Oggie Sutrisna
Jan 16
@oggiesutrisna
bun
emanon
Jan 16
@0x_emanon
✅ bun
yuki
Jan 16
@staticdots
bun
SpiritBear
Jan 16
@0xSpiritBear
bun
Ayu
Jan 12
@Ayuu2809
Bun good 🧅
Hirbod
Jan 19
@hirbod_dev
For everything. Yes. I even run with bunx expo run:ios etc
Luis Paolini
Jan 18
@DigitalLuiggi
Jus use @bunjavascript
buraks
Jan 18
@buraks____
I use bun patch and I love it!
fahadali
Jan 8
@fahadali503
Bun
Aiden Bai
Jan 1
@aidenybai
2025 will be the year of JS/TS and @bunjavascript is why
Catalin
Jan 1
@catalinmpit
Bun is goated
MadMax
Jan 3
@dr__madmax
@bunjavascript is yet to get enough appreciation it deserves.
Baggi/e
Jan 3
@ManiSohi
Performant TS/JS backend needs more love
Elysia for the win
Michael Feldstein
Dec 18
@msfeldstein
holy shit bun is the solution to spending all day mucking around with typescript/module/commonjs/import bullshit and just running scripts
Hirbod
Jan 19
@hirbod_dev
For everything. Yes. I even run with bunx expo run:ios etc
Luis Paolini
Jan 18
@DigitalLuiggi
Jus use @bunjavascript
buraks
Jan 18
@buraks____
I use bun patch and I love it!
fahadali
Jan 8
@fahadali503
Bun
Aiden Bai
Jan 1
@aidenybai
2025 will be the year of JS/TS and @bunjavascript is why
Catalin
Jan 1
@catalinmpit
Bun is goated
MadMax
Jan 3
@dr__madmax
@bunjavascript is yet to get enough appreciation it deserves.
Baggi/e
Jan 3
@ManiSohi
Performant TS/JS backend needs more love
Elysia for the win
Michael Feldstein
Dec 18
@msfeldstein
holy shit bun is the solution to spending all day mucking around with typescript/module/commonjs/import bullshit and just running scripts