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Catalogs share dependency versions across the packages in a monorepo. Rather than repeating the same versions in each workspace package, you define them once in the root package.json and reference them throughout your project.

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Overview

Instead of each workspace package specifying its own versions, you:
  1. Define version catalogs in the root package.json
  2. Reference those versions with the catalog: protocol
  3. Update every package at once by changing the version in one place
This matters most in large monorepos where dozens of packages depend on the same versions of key dependencies.

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How to Use Catalogs

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Directory Structure Example

Consider a monorepo with the following structure: 
my-monorepo/
├── package.json
├── bun.lock
└── packages/
    ├── app/
    │   └── package.json
    ├── ui/
    │   └── package.json
    └── utils/
        └── package.json

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1. Define Catalogs in Root package.json

In your root-level package.json, add a catalog or catalogs field within the workspaces object:
package.json
{
  "name": "my-monorepo",
  "workspaces": {
    "packages": ["packages/*"],
    "catalog": {
      "react": "^19.0.0",
      "react-dom": "^19.0.0"
    },
    "catalogs": {
      "testing": {
        "jest": "30.0.0",
        "testing-library": "14.0.0"
      }
    }
  }
}
catalog and catalogs also work at the top level of package.json.

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2. Reference Catalog Versions in Workspace Packages

In your workspace packages, use the catalog: protocol to reference versions:
packages/app/package.json
{
  "name": "app",
  "dependencies": {
    "react": "catalog:",
    "react-dom": "catalog:",
    "jest": "catalog:testing"
  }
}
packages/ui/package.json
{
  "name": "ui",
  "dependencies": {
    "react": "catalog:",
    "react-dom": "catalog:"
  },
  "devDependencies": {
    "jest": "catalog:testing",
    "testing-library": "catalog:testing"
  }
}

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3. Run Bun Install

Run bun install to install all dependencies according to the catalog versions.

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Catalog vs Catalogs

Bun supports two ways to define catalogs:
  1. catalog (singular): A single default catalog for commonly used dependencies
    package.json
    "catalog": {
  "react": "^19.0.0",
  "react-dom": "^19.0.0"
}
    Reference with catalog::
    packages/app/package.json
    "dependencies": {
  "react": "catalog:"
}
  2. catalogs (plural): Multiple named catalogs for grouping dependencies
    package.json
    "catalogs": {
  "testing": {
    "jest": "30.0.0"
  },
  "ui": {
    "tailwind": "4.0.0"
  }
}
    Reference with catalog:<name>:
    packages/app/package.json
    "dependencies": {
  "jest": "catalog:testing",
  "tailwind": "catalog:ui"
}

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Benefits of Using Catalogs

  • Consistency: All packages use the same version of critical dependencies
  • Maintenance: Update a dependency version in one place instead of across multiple package.json files
  • Clarity: Makes it obvious which dependencies are standardized across your monorepo
  • Simplicity: No extra version resolution strategies or external tools

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Real-World Example

A larger example, for a React application: Root package.json
package.json
{
  "name": "react-monorepo",
  "workspaces": {
    "packages": ["packages/*"],
    "catalog": {
      "react": "^19.0.0",
      "react-dom": "^19.0.0",
      "react-router-dom": "^6.15.0"
    },
    "catalogs": {
      "build": {
        "webpack": "5.88.2",
        "babel": "7.22.10"
      },
      "testing": {
        "jest": "29.6.2",
        "react-testing-library": "14.0.0"
      }
    }
  },
  "devDependencies": {
    "typescript": "5.1.6"
  }
}
packages/app/package.json
{
  "name": "app",
  "dependencies": {
    "react": "catalog:",
    "react-dom": "catalog:",
    "react-router-dom": "catalog:",
    "@monorepo/ui": "workspace:*",
    "@monorepo/utils": "workspace:*"
  },
  "devDependencies": {
    "webpack": "catalog:build",
    "babel": "catalog:build",
    "jest": "catalog:testing",
    "react-testing-library": "catalog:testing"
  }
}
packages/ui/package.json
{
  "name": "@monorepo/ui",
  "dependencies": {
    "react": "catalog:",
    "react-dom": "catalog:"
  },
  "devDependencies": {
    "jest": "catalog:testing",
    "react-testing-library": "catalog:testing"
  }
}
packages/utils/package.json
{
  "name": "@monorepo/utils",
  "dependencies": {
    "react": "catalog:"
  },
  "devDependencies": {
    "jest": "catalog:testing"
  }
}

​
Updating Versions

To update versions across all packages, change the version in the root package.json:
package.json
"catalog": {
  "react": "^19.1.0",  // Updated from ^19.0.0
  "react-dom": "^19.1.0"  // Updated from ^19.0.0
}
Then run bun install to update all packages.

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Lockfile Integration

Bun’s lockfile tracks catalog versions, so installs are consistent across environments. The lockfile includes:
  • The catalog definitions from your package.json
  • The resolution of each cataloged dependency
bun.lock(excerpt)
{
  "lockfileVersion": 2,
  "workspaces": {
    "": {
      "name": "react-monorepo",
    },
    "packages/app": {
      "name": "app",
      "dependencies": {
        "react": "catalog:",
        "react-dom": "catalog:",
        ...
      },
    },
    ...
  },
  "catalog": {
    "react": "^19.0.0",
    "react-dom": "^19.0.0",
    ...
  },
  "catalogs": {
    "build": {
      "webpack": "5.88.2",
      ...
    },
    ...
  },
  "packages": {
    ...
  }
}

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Limitations and Edge Cases

  • Catalog references must match a dependency defined in either catalog or one of the named catalogs
  • Empty strings and whitespace in catalog names are ignored (treated as default catalog)
  • Invalid dependency versions in catalogs fail to resolve during bun install
  • Catalogs are only available within workspaces; they cannot be used outside the monorepo

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Publishing

When you run bun publish or bun pm pack, Bun replaces catalog: references in your package.json with the resolved version numbers. The published package includes regular semver strings and no longer depends on your catalog definitions.