TL;DR

A CODEOWNERS file, when used on GitHub, exists in repo-name/.github/CODEOWNERS , it is a representation of who knows what about your repository. This file is used by GitHub to enable great automations including: automatically notifying codeowners of new Pull Requests and you can block merges unless a codeowner approves the PR.

Docs from GitHub about CODEOWNERS can be found here: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners

The File

• The CODEOWNERS file represents the code ownership across the repository.

• Users or teams can own parts of the codebase at the directory or file level

• What does it mean to be a code owner?
• At every organization this is different, but in general this means that if you’re a code owner, you will be the ‘go to’ person for this portion of the code.
• This means that you’ll be the one reviewing PR’s for changes to that code, or if anyone has any questions for that code they’ll be asking you.
• We’ve found that for large organizations this is really helpful! It’s quite common to not know who should review your changes, or even who to ask!

Automatic Pull Request Review Assignment

• In Github you can set up reviewers to be assigned automatically based on code ownership

• Once you have a valid CODEOWNERS file, GitHub will automatically start assigning code owners as reviewers 🎉

Blocking Merges by Requiring Code Owner Reviews

If you want to enable blocking merges unless a code owner reviews the PR you can via branch protection rules in GitHub:

For all the details from GitHub directly, checkout their docs here: https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/about-protected-branches#require-pull-request-reviews-before-merging

And extra detail on using branch protection rules here: https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/managing-a-branch-protection-rule

No more ‘whoops’ to the critical parts of your code 🔒