A CODEOWNERS file is a configuration tool used in Git repositories to designate specific users or teams as responsible for certain areas of the codebase, which enhances security, accountability, and efficiency in the code review process. It is particularly useful in monorepo settings, where multiple projects reside within a single repository, by ensuring that the appropriate stakeholders review code changes. The file allows for flexible assignment of ownership, using patterns and wildcards to specify files or directories, and can be stored in various locations within the repository. Although CODEOWNERS are linked to pull requests, they are not automatically assigned as reviewers to avoid unnecessary notifications, but their involvement can be requested manually. Best practices for using a CODEOWNERS file include defining ownership with appropriate granularity, maintaining consistency in ownership assignments, documenting the file's purpose and structure, and regularly testing to ensure accuracy. Dewan Ahmed, the author, is a Principal Developer Advocate at Harness and has extensive experience in solving DevOps and infrastructure challenges, with a commitment to fostering collaboration and maintaining code quality.