Bun — All-in-One JavaScript Runtime

Bun Performance

Package Manager

# Install all dependencies (lockfile-aware)
bun install          # 25x faster than npm install

# Add a package
bun add openai
bun add -d typescript

# Remove
bun remove express

# Compatible with package.json and node_modules

Native TypeScript

// No tsconfig needed, no ts-node, no build step
const response: Response = await fetch("https://api.openai.com/v1/models");
const data: { data: Array<{ id: string }> } = await response.json();
console.log(data.data.map(m => m.id));

bun run app.ts  # Just works

Built-in Test Runner

// app.test.ts
import { expect, test } from "bun:test";

test("2 + 2 = 4", () => {
    expect(2 + 2).toBe(4);
});

test("fetch works", async () => {
    const res = await fetch("https://httpbin.org/get");
    expect(res.status).toBe(200);
});

bun test  # Runs all .test.ts files

Built-in Bundler

bun build ./src/index.ts --outdir ./dist --target browser

SQLite Built-in

import { Database } from "bun:sqlite";

const db = new Database("mydb.sqlite");
db.run("CREATE TABLE IF NOT EXISTS chats (id INTEGER PRIMARY KEY, prompt TEXT, response TEXT)");
db.run("INSERT INTO chats (prompt, response) VALUES (?, ?)", ["Hello", "Hi there!"]);

FAQ

Q: What is Bun? A: Bun is an all-in-one JavaScript/TypeScript runtime with 88,700+ GitHub stars. It replaces Node.js (runtime), npm (package manager), webpack (bundler), and Jest (test runner) in a single fast tool.

Q: Is Bun compatible with Node.js? A: Yes, Bun is largely compatible with Node.js APIs and npm packages. Most Express, Fastify, and Next.js apps work with Bun with minimal changes.

Q: Is Bun free? A: Yes, open-source under MIT license.