Bun

Fast all-in-one JavaScript runtime, bundler, test runner, and package manager.

Quick Start

# Create new project
bun init

# Install dependencies
bun install

# Run a script
bun run ./file.ts

# Run tests
bun test

Contents

• Package Management
• Running Code
• Testing
• Building
• Configuration
• Workspaces
• Environment Variables

Package Management

Installation

bun add <pkg>              # Production dep
bun add -d <pkg>           # Dev dependency
bun add --optional <pkg>   # Optional dep
bun add -g <pkg>           # Global install

Management

bun remove <pkg>           # Remove package
bun update                 # Update all
bun outdated               # Show outdated
bun audit                  # Security audit
bun why <pkg>              # Why installed
bun info <pkg>             # Show package metadata
bun publish                # Publish to npm
bun patch <pkg>            # Patch a package
bun link                   # Link local package
bun unlink                 # Unlink local package

See Package Management for details.

Running Code

bun run ./file.ts          # Execute file
bun run dev               # Run script
bun -e "code"             # Eval code
bun exec ./script.sh      # Run shell script

# Long-running/watch mode (use tmux for background)
tmux new -d -s dev 'bun run --watch ./file.ts'
tmux new -d -s hot 'bun run --hot ./file.ts'
tmux new -d -s repl 'bun repl'

See Running Code for details.

Testing

bun test                   # Run all tests
bun test --coverage       # With coverage
bun test -t "pattern"     # Filter by name
bun test --bail 3         # Stop after N failures
bun test -u               # Update snapshots

# Watch mode (use tmux for background)
tmux new -d -s test 'bun test --watch'

See Testing for details.

Building

bun build ./src/index.ts              # Bundle
bun build --production ./src/index.ts # Minified
bun build --target=node ./src/index.ts # Node target
bun build --compile ./cli.ts          # Executable
bun build --splitting ./src/index.ts  # Code splitting

See Building for details.

Configuration

bunfig.toml

[install]
linker = "hoisted"           # or "isolated"
minimumReleaseAge = 259200   # Security (3 days)
optional = true

[test]
timeout = 5000
coverage = { reporter = ["text"] }

[build]
minify = true
sourcemap = "external"

See Configuration for details.

Workspaces

Root package.json

{
  "workspaces": ["packages/*"],
  "catalog": {
    "react": "^18.0.0",
    "typescript": "^5.0.0"
  }
}

Workspace Commands

bun run --workspaces test    # Run in all workspaces
bun add <pkg> --filter <ws>  # Add to specific workspace
bun remove <pkg> --filter <ws> # Remove from workspace

See Workspaces for details.

Environment Variables

bun run --env-file=.env dev  # Load .env
process.env.VAR             # Access in code

See Environment Variables for details.

Tips

• Use bunx for one-off CLIs (auto-installs)
• Commit bun.lock for reproducible installs
• --frozen-lockfile in CI to prevent changes
• bun run -i auto-installs missing deps
• Standalone executables: bun build --compile
• Use tmux for watch/hot modes: tmux new -d -s dev 'bun run --watch'

Related Skills

• typescript: TypeScript configuration and type checking
• vitest: Test utilities and mocking
• ast-grep: Pattern matching for refactoring