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The bun why command explains why a package is installed in your project by showing the dependency chain that led to its installation.

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Usage

terminal
bun why <package>

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Arguments

  • <package>: The name of the package to explain. Supports glob patterns like @org/* or *-lodash.

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Options

  • --top: Show only the top-level dependencies instead of the complete dependency tree.
  • --depth <number>: Maximum depth of the dependency tree to display.

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Examples

Check why a specific package is installed:
terminal
bun why react

react@18.2.0
  └─ my-app@1.0.0 (requires ^18.0.0)
Check why all packages with a specific pattern are installed:
terminal
bun why "@types/*"

@types/react@18.2.15
  └─ dev my-app@1.0.0 (requires ^18.0.0)

@types/react-dom@18.2.7
  └─ dev my-app@1.0.0 (requires ^18.0.0)
Show only top-level dependencies:
terminal
bun why express --top

express@4.18.2
  └─ my-app@1.0.0 (requires ^4.18.2)
Limit the dependency tree depth:
terminal
bun why express --depth 2

express@4.18.2
  └─ express-pollyfill@1.20.1 (requires ^4.18.2)
     └─ body-parser@1.20.1 (requires ^1.20.1)
     └─ accepts@1.3.8 (requires ^1.3.8)
        └─ (deeper dependencies hidden)

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Understanding the Output

The output shows:
  • The package name and version being queried
  • The dependency chain that led to its installation
  • The type of dependency (dev, peer, optional, or production)
  • The version requirement specified in each package’s dependencies
For nested dependencies, the command shows the complete dependency tree by default, with indentation indicating the relationship hierarchy.
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