lockfile-lint is a tool that helps developers lint their lockfiles to ensure they adhere to pre-defined security policies and mitigate the risk of malicious packages being injected into the lockfile. Lockfiles are used as a trusted manifest of resources to fetch packages from, but keeping track of changes to lockfiles can be challenging as they are designed to be consumed by machines. The tool can be easily invoked using the npx command and can lint both yarn.lock and npm-shrinkwrap.json files. It checks the lockfile against a set of predefined security policies, such as ensuring that only trusted package hosts are used and that HTTPS is used for all package downloads. If the lockfile passes the lint checks, the tool will report no issues. If it detects any exceptions to the security policies, it will report them, allowing developers to address the issues and ensure the integrity of their lockfile. lockfile-lint can be used as a standalone CLI tool or as a programmatic API library, making it easy to integrate into existing development workflows, such as pre-commit hooks or CI/CD pipelines.