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
• <code class="ra0-md-code">bun init</code>
• <code class="ra0-md-code">bun create</code>

• Runtime
• <code class="ra0-md-code">bun run</code>
• 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
• <code class="ra0-md-code">bun install</code>
• <code class="ra0-md-code">bun add</code>
• <code class="ra0-md-code">bun remove</code>
• <code class="ra0-md-code">bun update</code>
• <code class="ra0-md-code">bun link</code>
• <code class="ra0-md-code">bun pm</code>
• <code class="ra0-md-code">bun outdated</code>
• <code class="ra0-md-code">bun publish</code>
• <code class="ra0-md-code">bun patch</code>
• <code class="ra0-md-code">bun why</code>
• <code class="ra0-md-code">bun audit</code>
• <code class="ra0-md-code">bun info</code>
• Global cache
• Global store
• Isolated installs
• Workspaces
• Catalogs
• Lifecycle scripts
• Filter
• Lockfile
• Scopes and registries
• Overrides and resolutions
• Security scanner API
• <code class="ra0-md-code">.npmrc</code>

• Bundler
• <code class="ra0-md-code">Bun.build</code>
• 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
• <code class="ra0-md-code">bun test</code>
• Writing tests
• Lifecycle hooks
• Mocks
• Snapshots
• Dates and times
• DOM testing
• Code coverage
• Configuration
• Discovery
• Reporters
• Runtime Behavior

• Package runner
• <code class="ra0-md-code">bunx</code>

• API
• HTTP server (<code class="ra0-md-code">Bun.serve</code>)
• HTTP routing
• HTTP error handling
• HTTP metrics
• WebSockets
• Workers
• Binary data
• Streams
• File I/O (<code class="ra0-md-code">Bun.file</code>)
• Archive (tar)
• SQLite (<code class="ra0-md-code">bun:sqlite</code>)
• PostgreSQL (<code class="ra0-md-code">Bun.sql</code>)
• Redis (<code class="ra0-md-code">Bun.redis</code>)
• S3 Client (<code class="ra0-md-code">Bun.s3</code>)
• FileSystemRouter
• TCP sockets
• UDP sockets
• Globals
• Child processes (spawn)
• Cron (<code class="ra0-md-code">Bun.cron</code>)
• WebView
• Transpiler (<code class="ra0-md-code">Bun.Transpiler</code>)
• Hashing
• Colors (<code class="ra0-md-code">Bun.color</code>)
• Console
• FFI (<code class="ra0-md-code">bun:ffi</code>)
• C Compiler (<code class="ra0-md-code">bun:ffi</code> cc)
• HTMLRewriter
• Cookies (<code class="ra0-md-code">Bun.Cookie</code>)
• CSRF (<code class="ra0-md-code">Bun.CSRF</code>)
• Secrets (<code class="ra0-md-code">Bun.secrets</code>)
• YAML (<code class="ra0-md-code">Bun.YAML</code>)
• TOML (<code class="ra0-md-code">Bun.TOML</code>)
• JSON5
• JSONL
• Markdown
• Image processing
• Utils
• Node-API
• Glob (<code class="ra0-md-code">Bun.Glob</code>)
• Semver (<code class="ra0-md-code">Bun.semver</code>)
• 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 <code class="ra0-md-code">bun test</code>
• Bail early with the Bun test runner
• Mock functions in <code class="ra0-md-code">bun test</code>
• Run tests in watch mode with Bun
• Use snapshot testing in <code class="ra0-md-code">bun test</code>
• Skip tests with the Bun test runner
• Using Testing Library with Bun
• Update snapshots in <code class="ra0-md-code">bun test</code>
• 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.