whyinstall

CLI tool to find why a dependency exists in your JS/TS project. Works with npm, yarn, and pnpm.

Installation

npm install -g whyinstall

Or use with npx:

npx whyinstall <package-name>

Usage

whyinstall lodash

Options

• -j, --json - Output results as JSON
• -c, --cwd <path> - Set working directory (default: current directory)
• -s, --size-map - Show bundle size impact breakdown

Features

• Works with npm, Yarn, and pnpm (auto-detection)
• Shows dependency chains for any package
• Displays dependency type (prod, dev, peer, optional)
• Shows package description, version, and size
• Finds source files that actually use the package
• Colored tree output for readability
• JSON output for CI/CD
• Actionable suggestions for optimization
• Bundle size impact breakdown

Example Output

whyinstall chalk

chalk v5.3.0 (43 KB)
  Terminal string styling done right

  installed via 1 path

1. prod
   whyinstall
   └─> chalk

Used in (2):
  src/cli.ts
  src/formatter.ts

Suggested actions:
  1. Can be removed from direct dependencies - it's installed transitively

Size Map Output

whyinstall next --size-map

Size map for: next

next total impact: 66.69 MB

Breakdown:
- next: 63.08 MB
- caniuse-lite: 2.19 MB
- styled-jsx: 971 KB
- @swc/helpers: 190 KB
- source-map-js: 104 KB
- postcss: 101 KB
- tslib: 60 KB
- nanoid: 20 KB
- @next/env: 10 KB
- picocolors: 3 KB
- client-only: 144 B

This package contributes 44.7% of your vendor bundle.

Development

npm install
npm run build
npm link

License

MIT