Bun

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What is Bun?

Bun is an all-in-one toolkit for JavaScript and TypeScript apps. It ships as a single executable called bun.

At its core is the Bun runtime, a fast JavaScript runtime designed as a drop-in replacement for Node.js. It's written in Rust and powered by JavaScriptCore under the hood, dramatically reducing startup times and memory usage.

bun run index.tsx             # TS and JSX supported out-of-the-box

The bun command-line tool also implements a test runner, script runner, and Node.js-compatible package manager. Instead of 1,000 node_modules for development, you only need bun. Bun's built-in tools are significantly faster than existing options and usable in existing Node.js projects with little to no changes.

bun test                      # run tests
bun run start                 # run the start script in package.json
bun install <pkg>             # install a package
bunx cowsay 'Hello, world!'   # execute a package

Install

Bun supports Linux (x64 & arm64), macOS (x64 & Apple Silicon), and Windows (x64 & arm64).

Linux users — Kernel version 5.6 or higher is strongly recommended, but the minimum is 5.1.

x64 users — if you see "illegal instruction" or similar errors, check our CPU requirements

# with install script (recommended)
curl -fsSL https://bun.com/install | bash
on windows
powershell -c "irm bun.sh/install.ps1 | iex"
with npm
npm install -g bun
with Homebrew
brew tap oven-sh/bun
brew install bun
with Docker
docker pull oven/bun
docker run --rm --init --ulimit memlock=-1:-1 oven/bun

Upgrade

To upgrade to the latest version of Bun, run:

bun upgrade

Bun automatically releases a canary build on every commit to main. To upgrade to the latest canary build, run:

bun upgrade --canary

View canary build

Quick links

• Intro

- What is Bun? - Installation - Quickstart - TypeScript - TypeScript 6

• Templating

- bun init - bun create

• Runtime

- bun run - File types (Loaders) - JSX - Environment variables - Bun APIs - Web APIs - Node.js compatibility - Plugins - Watch mode / Hot Reloading - Module resolution - Auto-install - bunfig.toml - Debugger - REPL - $ Shell

• Package manager

- bun install - bun add - bun remove - bun update - bun link - bun pm - bun outdated - bun publish - bun patch - bun why - bun audit - bun info - Global cache - Global store - Isolated installs - Workspaces - Catalogs - Lifecycle scripts - Filter - Lockfile - Scopes and registries - Overrides and resolutions - Security scanner API - .npmrc

• Bundler

- Bun.build - Loaders - Plugins - Macros - vs esbuild - Single-file executable - CSS - HTML & static sites - Hot Module Replacement (HMR) - Full-stack with HTML imports - Standalone HTML - Bytecode caching - Minifier

• Test runner

- bun test - Writing tests - Lifecycle hooks - Mocks - Snapshots - Dates and times - DOM testing - Code coverage - Configuration - Discovery - Reporters - Runtime Behavior

• Package runner

- bunx

• API

- HTTP server (Bun.serve) - HTTP routing - HTTP error handling - HTTP metrics - WebSockets - Workers - Binary data - Streams - File I/O (Bun.file) - Archive (tar) - SQLite (bun:sqlite) - PostgreSQL (Bun.sql) - Redis (Bun.redis) - S3 Client (Bun.s3) - FileSystemRouter - TCP sockets - UDP sockets - Globals - Child processes (spawn) - Cron (Bun.cron) - WebView - Transpiler (Bun.Transpiler) - Hashing - Colors (Bun.color) - Console - FFI (bun:ffi) - C Compiler (bun:ffi cc) - HTMLRewriter - Cookies (Bun.Cookie) - CSRF (Bun.CSRF) - Secrets (Bun.secrets) - YAML (Bun.YAML) - TOML (Bun.TOML) - JSON5 - JSONL - Markdown - Image processing - Utils - Node-API - Glob (Bun.Glob) - Semver (Bun.semver) - DNS - fetch API extensions

Guides

• Deployment

- Deploy to Vercel - Deploy to Railway - Deploy to Render - Deploy to AWS Lambda - Deploy to DigitalOcean - Deploy to Google Cloud Run

• Binary

- Convert a Blob to a string - Convert a Buffer to a blob - Convert a Blob to a DataView - Convert a Buffer to a string - Convert a Blob to a ReadableStream - Convert a Blob to a Uint8Array - Convert a DataView to a string - Convert a Uint8Array to a Blob - Convert a Blob to an ArrayBuffer - Convert an ArrayBuffer to a Blob - Convert a Buffer to a Uint8Array - Convert a Uint8Array to a Buffer - Convert a Uint8Array to a string - Convert a Buffer to an ArrayBuffer - Convert an ArrayBuffer to a Buffer - Convert an ArrayBuffer to a string - Convert a Uint8Array to a DataView - Convert a Buffer to a ReadableStream - Convert a Uint8Array to an ArrayBuffer - Convert an ArrayBuffer to a Uint8Array - Convert an ArrayBuffer to an array of numbers - Convert a Uint8Array to a ReadableStream

• Ecosystem

- Use React and JSX - Use Gel with Bun - Use Prisma with Bun - Use Prisma Postgres with Bun - Add Sentry to a Bun app - Create a Discord bot - Run Bun as a daemon with PM2 - Use Drizzle ORM with Bun - Use Upstash Redis with Bun - Build an app with Nuxt and Bun - Build an app with Qwik and Bun - Build an app with Astro and Bun - Build an app with Remix and Bun - Build a frontend using Vite and Bun - Build an app with Next.js and Bun - Run Bun as a daemon with systemd - Build an HTTP server using Hono and Bun - Build an app with SvelteKit and Bun - Build an app with SolidStart and Bun - Build an app with TanStack Start and Bun - Build an HTTP server using Elysia and Bun - Build an HTTP server using StricJS and Bun - Containerize a Bun application with Docker - Build an HTTP server using Express and Bun - Use Neon Postgres through Drizzle ORM - Server-side render (SSR) a React component - Read and write data to MongoDB using Mongoose and Bun - Use Neon's Serverless Postgres with Bun

• HTMLRewriter

- Extract links from a webpage using HTMLRewriter - Extract social share images and Open Graph tags

• HTTP

- Hot reload an HTTP server - Common HTTP server usage - Write a simple HTTP server - Configure TLS on an HTTP server - Send an HTTP request using fetch - Proxy HTTP requests using fetch() - Start a cluster of HTTP servers - Stream a file as an HTTP Response - fetch with unix domain sockets in Bun - Upload files via HTTP using FormData - Streaming HTTP Server with Async Iterators - Streaming HTTP Server with Node.js Streams - Server-Sent Events (SSE) with Bun

• Install

- Add a dependency - Add a Git dependency - Add a peer dependency - Add a trusted dependency - Add a development dependency - Add a tarball dependency - Add an optional dependency - Generate a yarn-compatible lockfile - Configuring a monorepo using workspaces - Install a package under a different name - Install dependencies with Bun in GitHub Actions - Using bun install with Artifactory - Configure git to diff Bun's lockb lockfile - Override the default npm registry for bun install - Using bun install with an Azure Artifacts npm registry - Migrate from npm install to bun install - Configure a private registry for an organization scope with bun install

• Process

- Read from stdin - Listen for CTRL+C - Spawn a child process - Listen to OS signals - Parse command-line arguments - Read stderr from a child process - Read stdout from a child process - Get the process uptime in nanoseconds - Spawn a child process and communicate using IPC

• Read file

- Read a JSON file - Check if a file exists - Read a file as a string - Read a file to a Buffer - Get the MIME type of a file - Watch a directory for changes - Read a file as a ReadableStream - Read a file to a Uint8Array - Read a file to an ArrayBuffer

• Runtime

- Delete files - Run a Shell Command - Import a JSON file - Import a TOML file - Import a YAML file - Import a JSON5 file - Set a time zone in Bun - Set environment variables - Re-map import paths - Delete directories - Read environment variables - Import a HTML file as text - Install and run Bun in GitHub Actions - Debugging Bun with the web debugger - Install TypeScript declarations for Bun - Debugging Bun with the VS Code extension - Inspect memory usage using V8 heap snapshots - Define and replace static globals & constants - Build-time constants with --define - Codesign a single-file JavaScript executable on macOS

• Streams

- Convert a ReadableStream to JSON - Convert a ReadableStream to a Blob - Convert a ReadableStream to a Buffer - Convert a ReadableStream to a string - Convert a ReadableStream to a Uint8Array - Convert a ReadableStream to an array of chunks - Convert a Node.js Readable to JSON - Convert a ReadableStream to an ArrayBuffer - Convert a Node.js Readable to a Blob - Convert a Node.js Readable to a string - Convert a Node.js Readable to an Uint8Array - Convert a Node.js Readable to an ArrayBuffer

• Test

- Spy on methods in bun test - Bail early with the Bun test runner - Mock functions in bun test - Run tests in watch mode with Bun - Use snapshot testing in bun test - Skip tests with the Bun test runner - Using Testing Library with Bun - Update snapshots in bun test - Run your tests with the Bun test runner - Set the system time in Bun's test runner - Set a per-test timeout with the Bun test runner - Migrate from Jest to Bun's test runner - Write browser DOM tests with Bun and happy-dom - Mark a test as a "todo" with the Bun test runner - Re-run tests multiple times with the Bun test runner - Generate code coverage reports with the Bun test runner - import, require, and test Svelte components with bun test - Set a code coverage threshold with the Bun test runner - Selectively run tests concurrently with glob patterns

• Util

- Generate a UUID - Hash a password - Escape an HTML string - Get the current Bun version - Upgrade Bun to the latest version - Encode and decode base64 strings - Compress and decompress data with gzip - Sleep for a fixed number of milliseconds - Detect when code is executed with Bun - Check if two objects are deeply equal - Compress and decompress data with DEFLATE - Get the absolute path to the current entrypoint - Get the directory of the current file - Check if the current file is the entrypoint - Get the file name of the current file - Convert a file URL to an absolute path - Convert an absolute path to a file URL - Get the absolute path of the current file - Get the path to an executable bin file

• WebSocket

- Build a publish-subscribe WebSocket server - Build a simple WebSocket server - Enable compression for WebSocket messages - Set per-socket contextual data on a WebSocket

• Write file

- Delete a file - Write to stdout - Write a file to stdout - Write a Blob to a file - Write a string to a file - Append content to a file - Write a file incrementally - Write a Response to a file - Copy a file to another location - Write a ReadableStream to a file

Contributing

Refer to the Project > Contributing guide to start contributing to Bun.

License

Refer to the Project > License page for information about Bun's licensing.