What is Code Review?
The practice of having peers examine proposed code changes for correctness, design, and maintainability before merging.
Definition
Code review routes every change through at least one other engineer, typically as a GitHub or GitLab pull request, catching defects early while spreading knowledge of the codebase and its conventions. Effective reviews focus on what automation can't: correctness of logic, API design, naming, test adequacy, and security implications—while linters, formatters, and CI handle style disputes mechanically. Research (including Google's and SmartBear's studies) shows small changesets under ~400 lines get meaningfully better review; huge diffs get rubber-stamped. Team norms matter: fast turnaround, comments phrased as questions, and explicit severity labels (nit vs. blocking) keep review a multiplier rather than a bottleneck. AI reviewers now provide a useful first pass.