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• bun outdated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.