Bun Package Manager: The Fastest JavaScript Runtime and Package Manager in 2026

Bun is an all-in-one JavaScript runtime and toolkit written in Zig. Its package manager installs dependencies up to 23x faster than npm by using a binary lockfile, a global package cache, and symlink-based node_modules. In 2026, Bun 1.x has become a serious alternative to the Node.js ecosystem for both development and production.

Installation and Basic Commands

Bun installs in seconds and works as a drop-in replacement for npm commands. It reads package.json, installs to node_modules, and supports all npm registry packages.

# Install Bun
curl -fsSL https://bun.sh/install | bash

# Verify installation
bun --version  # 1.x.x

# Install dependencies (reads package.json)
bun install

# Install a specific package
bun add express
bun add -d typescript @types/node   # dev dependency
bun add -g bunx                     # global install

# Remove a package
bun remove lodash

# Update all packages
bun update

# Run a script from package.json
bun run build
bun run dev

# Execute a TypeScript file directly (no transpile step)
bun run index.ts

Workspaces (Monorepo Support)

Bun supports npm-style workspaces for monorepos. Use --filter to run scripts across all workspaces, or target specific packages.

// package.json — monorepo root
{
  "name": "my-monorepo",
  "workspaces": [
    "packages/*",
    "apps/*"
  ],
  "scripts": {
    "dev": "bun run --filter '*' dev",
    "build": "bun run --filter '*' build",
    "test": "bun test"
  }
}

// Run a script only in specific workspace
bun run --filter @myapp/web dev

// Install a dependency in a specific workspace
bun add react --cwd apps/web

// Link a local workspace package
// (Bun automatically resolves workspace: protocol)

The Binary Lockfile (bun.lockb)

Bun uses a binary lockfile (bun.lockb) instead of JSON. It is dramatically faster to parse than package-lock.json or yarn.lock, which is why bun install is so fast.

# bun.lockb is a binary lockfile (much faster to parse than JSON)
# To view lockfile contents in human-readable form:
bun bun.lockb  # prints as yarn.lock format

# To regenerate lockfile:
bun install --frozen-lockfile  # CI: fails if lockfile is stale

# Migrating from npm/yarn/pnpm:
# Bun reads package-lock.json, yarn.lock, pnpm-lock.yaml
# to preserve existing versions on first install

# .gitignore for Bun:
# node_modules/
# *.lock  (optional — commit bun.lockb for reproducible installs)

Performance Benchmarks

Bun's package manager is substantially faster than all alternatives due to its native code (Zig), binary lockfile, parallel downloads, and global cache.

# Benchmark: installing react + 1400 packages
# (warm cache, MacBook M2 Pro)

npm install:   28.3s
yarn install:  14.1s
pnpm install:   9.4s
bun install:    1.2s   # 23x faster than npm!

# Cold cache (first install, no node_modules)
npm install:   38.7s
bun install:    4.1s   # 9x faster

# bun install uses:
# - Symlink-based node_modules (like pnpm)
# - Binary lockfile (bun.lockb) for fast parsing
# - Parallel downloads
# - Global package cache (~/.bun/install/cache)
# - Native code (written in Zig)

bunx and Built-in Tools

bunx runs packages without downloading — it uses cached binaries. Bun also includes a built-in test runner (Jest-compatible), TypeScript runner, bundler, and .env loader.

# bunx — like npx but instant (no download delay)
bunx create-next-app@latest my-app
bunx prettier --write .
bunx eslint src/

# Run TypeScript directly
bun index.ts            # works without ts-node or compilation
bun --watch server.ts   # auto-restart on file changes

# Bun's built-in test runner (Jest-compatible API)
bun test
bun test --watch
bun test src/utils.test.ts

// Example test file
import { expect, test, describe } from 'bun:test';

describe('math', () => {
    test('adds numbers', () => {
        expect(1 + 2).toBe(3);
    });

    test('async operations', async () => {
        const result = await fetch('https://api.example.com/data');
        expect(result.ok).toBe(true);
    });
});

Scripts and Build Integration

Bun runs package.json scripts faster than npm/yarn because it avoids spinning up a new Node.js process. It also includes a built-in bundler that can replace esbuild for simple use cases.

// package.json scripts with Bun
{
  "scripts": {
    "dev": "bun --watch src/index.ts",
    "build": "bun build src/index.ts --outdir dist --target node",
    "bundle:web": "bun build src/app.ts --outdir public/js --target browser --minify",
    "test": "bun test",
    "lint": "bunx eslint src/",
    "format": "bunx prettier --write src/"
  }
}

// Bun's built-in bundler (replaces esbuild/webpack for simple cases)
// bun build src/index.ts --outdir dist --target node --minify

// Environment variables (Bun auto-loads .env files)
// No need for dotenv package!
console.log(process.env.DATABASE_URL); // works in Bun automatically

Bun vs npm vs pnpm vs Yarn

Best Practices

• Commit bun.lockb to version control for reproducible installs. Use --frozen-lockfile in CI to catch lockfile drift.
• Use bun --watch for development — it is faster than nodemon or ts-node-dev and works with TypeScript natively.
• Migrate from npm scripts gradually: replace npm run with bun run and npm install with bun install first.
• For monorepos, Bun workspaces are simpler than Turborepo's configuration but pair well with it for task caching.
• Bun auto-loads .env, .env.local, .env.production — no dotenv package needed. Use this to simplify config.

Frequently Asked Questions