Branch protection is a set of rules a Git hosting platform enforces on a specific branch — such as requiring passing status checks, requiring reviewer approval, or blocking force-pushes and deletions — before any pull request targeting that branch can merge.
Common protections include required status checks (automated tests or scans that must pass), required reviewer approvals, a "strict" or up-to-date requirement (the branch must include the latest commits from its target before merging), and hard blocks on force-pushing, deleting, or renaming the branch. Platforms like 📝GitHub expose these as per-branch settings, typically configured differently for a fast-moving branch (light or no protection) versus a shared branch that deploys somewhere (heavier protection).
Branch protection matters most where multiple contributors — human or AI agents — merge into the same branch concurrently. A strict up-to-date requirement, for instance, rejects a merge if someone else merged first, forcing the later contributor to sync and retry — which serializes concurrent merges automatically, without a separate coordination system. Without it, two people merging around the same time can silently overwrite each other's work or leave the branch in a broken state.