Bun

Overview

Bun is an all-in-one JavaScript runtime and toolkit designed for speed. It replaces Node.js, npm, npx, Jest, Webpack, and ts-node with a single binary.

Core APIs

bun.serve

HTTP server with built-in request/response handling. Supports TLS, streaming, and WebSockets natively.

bun.file

Lazy file reader with BLOB support. Works with Response, ArrayBuffer, and streaming interfaces.

bun:sqlite

Built-in SQLite3 binding. Synchronous API, no C dependencies. Supports prepared statements, transactions, and WAL mode.

Package Management

• bun install — fast lockfile-free installs with global cache
• bun add / bun remove — dependency management
• bunx — npx-compatible package runner

Build System

Bun.build bundles JavaScript/TypeScript for browser and server. Supports entry points, external modules, minification, source maps, and targeting.

Plugin System

Bun plugins intercept module resolution and transformation. Useful for loaders (CSS, YAML, .env) and custom transpilation.

Test Runner

bun test provides Jest-compatible API (describe, it, expect) with TypeScript and JSX support, snapshots, and lifecycle hooks.

Node.js Compatibility

Bun aims for full Node.js API compatibility. Most npm packages work without modification. Built-in support for node:* modules, CommonJS, and ESM.