What is pnpm and how does it differ from npm and Yarn?

pnpm (Performant npm) is a fast, disk-space efficient JavaScript package manager.

Key Differences:

1. Storage Mechanism

   • pnpm: Uses content-addressable storage, all packages stored in global store, referenced via hard links in projects
   • npm/Yarn: Each project copies its own node_modules, consuming significant disk space

2. Installation Speed

   • pnpm: Extremely fast on subsequent installs due to hard linking
   • npm/Yarn: Requires re-downloading or copying files each time

3. Dependency Structure

   • pnpm: Uses non-flat node_modules structure, creates strict dependency trees via symlinks
   • npm/Yarn: Uses flat structure, may cause "phantom dependencies" issues

4. Disk Space

   • pnpm: Multiple projects share the same packages, saving 70%+ disk space
   • npm/Yarn: Each project stores independently, duplicating space usage

Example Comparison:

bash
# npm install
npm install lodash
# node_modules contains complete lodash copy

# pnpm install
pnpm add lodash
# node_modules contains only hard link to global store

Advantages Summary:

• Faster installation speed
• Less disk usage
• Stricter dependency management, avoiding phantom dependencies
• Better monorepo support