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 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 & 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

• Templating

  • bun init
  • bun create

• CLI

  • bun upgrade

• Runtime

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

• Package manager

  • bun install
  • bun add
  • bun remove
  • bun update
  • bun link
  • bun unlink
  • bun pm
  • bun outdated
  • bun publish
  • bun patch
  • bun patch-commit
  • Global cache
  • Workspaces
  • Lifecycle scripts
  • Filter
  • Lockfile
  • Scopes and registries
  • Overrides and resolutions
  • .npmrc

• Bundler

  • Bun.build
  • Loaders
  • Plugins
  • Macros
  • vs esbuild
  • Single-file executable
  • CSS
  • HTML
  • Hot Module Replacement (HMR)
  • Full-stack with HTML imports

• Test runner

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

• Package runner

  • bunx

• API

  • HTTP server (Bun.serve)
  • WebSockets
  • Workers
  • Binary data
  • Streams
  • File I/O (Bun.file)
  • import.meta
  • SQLite (bun:sqlite)
  • PostgreSQL (Bun.sql)
  • Redis (Bun.redis)
  • S3 Client (Bun.s3)
  • FileSystemRouter
  • TCP sockets
  • UDP sockets
  • Globals
  • $ Shell
  • Child processes (spawn)
  • Transpiler (Bun.Transpiler)
  • Hashing
  • Colors (Bun.color)
  • Console
  • FFI (bun:ffi)
  • C Compiler (bun:ffi cc)
  • HTMLRewriter
  • Testing (bun:test)
  • Cookies (Bun.Cookie)
  • Utils
  • Node-API
  • Glob (Bun.Glob)
  • Semver (Bun.semver)
  • DNS
  • fetch API extensions

Guides

• 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
  • Add Sentry to a Bun app
  • Create a Discord bot
  • Run Bun as a daemon with PM2
  • Use Drizzle ORM 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
  • Deploy a Bun application on Render
  • Build an HTTP server using Hono and Bun
  • Build an app with SvelteKit and Bun
  • Build an app with SolidStart 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

• 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
  • 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
  • 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

• Util

  • Generate a UUID
  • Hash a password
  • Escape an HTML string
  • Get the current Bun 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.