Bun

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What is Bun?

Bun is under active development. Use it to speed up your development workflows or run simpler production code in resource-constrained environments like serverless functions. We're working on more complete Node.js compatibility and integration with existing frameworks. Join the Discord and watch the GitHub repository to keep tabs on future releases.

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 Zig 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).

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

# with install script (recommended)
curl -fsSL https://bun.sh/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

• Templating

  • bun init
  • bun create

• Runtime

  • bun run
  • File types
  • TypeScript
  • JSX
  • Environment variables
  • Bun APIs
  • Web APIs
  • Node.js compatibility
  • Single-file executable
  • Plugins
  • Watch mode
  • Module resolution
  • Auto-install
  • bunfig.toml
  • Debugger
  • Framework API

• Package manager

  • bun install
  • bun add
  • bun remove
  • bun update
  • bun link
  • bun pm
  • Global cache
  • Workspaces
  • Lifecycle scripts
  • Filter
  • Lockfile
  • Scopes and registries
  • Overrides and resolutions

• Bundler

  • Bun.build
  • Loaders
  • Plugins
  • Macros
  • vs esbuild

• Test runner

  • bun test
  • Writing tests
  • Watch mode
  • Lifecycle hooks
  • Mocks
  • Snapshots
  • Dates and times
  • DOM testing
  • Code coverage

• Package runner

  • bunx

• API

  • HTTP server
  • WebSockets
  • Workers
  • Binary data
  • Streams
  • File I/O
  • import.meta
  • SQLite
  • FileSystemRouter
  • TCP sockets
  • UDP sockets
  • Globals
  • $ Shell
  • Child processes
  • Transpiler
  • Hashing
  • Console
  • FFI
  • HTMLRewriter
  • Testing
  • Utils
  • Node-API
  • Glob
  • Semver

• Project

  • Roadmap
  • Benchmarking
  • Contributing
  • Building Windows
  • License

Guides

• Binary

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

• Ecosystem

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

• HTTP

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

• Install

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

• Process

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

• Read file

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

• Runtime

  • Debugging Bun with the VS Code extension
  • Debugging Bun with the web debugger
  • Define and replace static globals & constants
  • Import a JSON file
  • Import a TOML file
  • Import HTML file as text
  • Install and run Bun in GitHub Actions
  • Install TypeScript declarations for Bun
  • Re-map import paths
  • Read environment variables
  • Run a Shell Command
  • Set a time zone in Bun
  • Set environment variables

• Streams

  • Convert a Node.js Readable to a Blob
  • Convert a Node.js Readable to a string
  • Convert a Node.js Readable to an ArrayBuffer
  • Convert a Node.js Readable 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 ReadableStream to an ArrayBuffer
  • Convert a ReadableStream to JSON

• Test

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

• Util

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

• 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

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

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.