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PR review

PR review: how to review a pull request on GitHub

By Ilya Volodarsky · Updated

A PR review is a second engineer reading a pull request before it merges. On GitHub you read it in the Files changed tab, comment on lines, and submit the review as Comment, Approve or Request changes.[1]

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Most real misses sit outside the diff: a test, migration, config value or second read path the change should have touched too. The steps below are GitHub's; the code review checklist is what to look for.

How to review a pull request on GitHub

  1. Read the description first

    Know what the change is meant to do, and which issue it closes, before you open the diff.

  2. Open Files changed

    Read one file at a time and mark each one Viewed; the header counts how many you have read.[1]

  3. Search outside the diff

    For anything renamed, removed or retyped, find its callers, tests, migrations and configs. In Keycloak #36880 the bug sat in a file the pull request never touched: it created per-client resources with no type, so a new lookup by type found none of them. On the code review benchmark DeepSeek V4.1 Flash, DeepSeek V4 Pro, Qodo and Bugbot flagged it.[2]

    Code ReviewOn Starter, Pro and Max

  4. Comment on the line, with the fix

    Name the input that breaks it and what happens. For a small fix, add a suggestion block the author can commit.[1]

  5. Submit the review

    Comment, Approve or Request changes. Request changes does not block the merge on its own; a ruleset or branch protection rule does.[1]

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FAQ

Frequently asked questions

How do I review a pull request on GitHub?

Open the pull request and click Files changed. Comment on lines as you read, then click Review changes and submit it as Comment, Approve or Request changes.

What should I check in a PR review?

That the change does what the description says, that a test covers it, that callers, migrations and configs outside the diff still work, that errors are handled, and that no secret lands in code or logs.

Does Request changes block a merge?

Not by itself. GitHub calls it purely informational unless a ruleset or branch protection rule requires a pull request; then the pull request cannot merge until that reviewer approves.

Can AI do a PR review?

As a first pass, yes. IonWarp's Code Review reviews every pull request and posts each finding with a suggested fix; a person still approves the merge.

Sources

  1. Reviewing proposed changes in a pull requestGitHub Docs · read
  2. keycloak/keycloak #36880 (client permissions), graded code review findingsIonWarp benchmark · read