What is Bun?

Bun is a fast, all-in-one toolkit for JavaScript and TypeScript development. It replaces multiple tools with a single runtime that includes a native bundler, transpiler, task runner, and npm client. Designed for incremental adoption, Bun works alongside existing Node.js projects or as a complete replacement stack. It aims for 100% Node.js compatibility while delivering dramatically faster performance for everyday tasks like installing packages, running tests, and building applications.

Who it's for

• JavaScript developers looking to speed up their development workflow with a runtime that bundles, transpiles, and runs code faster than traditional tools.
• Node.js project maintainers who want to adopt individual Bun tools like bun install or bun test without migrating their entire stack.
• TypeScript and JSX users seeking a runtime that handles these formats natively without separate configuration or build steps.

Key features

Blazing fast package manager

Bun's built-in npm client streams tarballs directly to disk, using 17x less memory than traditional package managers. This makes bun install significantly faster, especially in CI environments or on machines with limited resources.

Native bundler and transpiler

Bun can bundle 10,000 React components in 269 milliseconds — faster than esbuild, Rolldown, and other popular bundlers. It handles JavaScript, TypeScript, and JSX out of the box, eliminating the need for separate build tools.

Built-in test runner

The bun test command supports parallel execution, sharding, and isolation. It includes features like mock and spyOn with Symbol.dispose support, making it a drop-in replacement for existing test frameworks in many projects.

High-performance HTTP server

Bun delivers 59,026 requests per second for a basic Express.js "hello world" — roughly 3x faster than Node.js and over 2x faster than Deno. This makes it ideal for latency-sensitive web applications.

What stands out

Bun is a fast, incrementally adoptable all-in-one JavaScript, TypeScript & JSX toolkit.

This philosophy sets Bun apart from other runtimes. You don't need to rewrite your entire project to benefit — you can start by replacing just npm install or node commands. The performance gains compound as you adopt more of Bun's integrated tools, but there's no lock-in pressure. The bundler, test runner, and package manager all work independently, letting teams migrate at their own pace.

Worth checking out if…

You're tired of managing separate tools for bundling, testing, and package management, or if your Node.js projects are hitting performance bottlenecks. Bun is especially valuable for teams running large monorepos, CI pipelines with many install steps, or web applications that need faster cold starts and request handling. It's also a strong choice for TypeScript developers who want a runtime that understands their code without extra configuration.