Syncpack is a command-line utility designed to manage and enforce consistency across dependencies in large JavaScript monorepos and multi-package repositories. It helps teams ensure that shared dependencies across multiple packages use the same versions and follow consistent rules.

The tool scans all package.json files in a repository and detects mismatches such as different versions of the same dependency across packages, inconsistent semver ranges, or improperly formatted dependency declarations. It can then automatically fix these issues or report them for review.

Syncpack is commonly used in monorepo environments where multiple packages depend on shared libraries like React or utility packages. Without version enforcement, these environments can easily drift into dependency fragmentation, causing hard-to-debug inconsistencies. Syncpack solves this by allowing teams to define strict version policies and enforce them programmatically.

It provides both linting and fixing capabilities, along with flexible configuration through version groups. Developers can define rules such as enforcing exact versions, pinning specific dependencies, or ignoring certain packages. It also supports formatting package.json files to maintain consistent structure across a repository.

Key features include:

• Detecting and fixing dependency version mismatches across monorepos
• Enforcing consistent semver policies and version ranges
• Formatting and sorting package.json files consistently
• Support for dependency filtering and version grouping rules
• CLI commands for linting, fixing, listing, and updating dependencies

Common use cases include:

• Managing dependency consistency in monorepos
• Preventing version drift across packages
• Enforcing strict dependency policies in large teams
• Automating maintenance of package.json files in multi-package JavaScript projects.

Syncpack is an open-source project created and maintained by Jamie Mason.