Code Review

In Turkish: kod incelemesi

Updated September 30, 20262 min read

In short

A code review is the practice of having other developers check code changes before they are merged, to catch bugs, improve quality, and share knowledge.

What is a code review?

In a code review, one or more teammates read through a proposed change before it becomes part of the main codebase. They check that the code works, is easy to understand, follows the team's conventions, and doesn't introduce security problems or unnecessary complexity. The author then responds to the feedback, makes changes, and merges once reviewers approve.

Today, most code reviews happen in pull requests on hosting platforms such as GitHub, GitLab, or Bitbucket. Reviewers see a diff, a view of exactly which lines were added, removed, or changed, and can comment on specific lines, suggest edits, approve, or request changes. Automated tools usually run first, so linters, formatters, tests, and security scanners handle the mechanical checks, leaving humans to focus on logic, design, and readability.

A code review is like having a colleague proofread an important email before you send it: a fresh pair of eyes spots mistakes and unclear wording you've stopped noticing. Beyond catching bugs, reviews spread knowledge, since more than one person understands each part of the system, and they help newer developers learn the codebase. Many teams now add AI assistants as an extra reviewer, though a human usually still gives the final approval.

Code review is sometimes confused with testing. Tests check behavior automatically, while a review checks things tests can't, such as whether the approach makes sense and whether the next developer will understand it. Good reviews are timely, focus on the code rather than the person, and work best on small changes, because reviewing hundreds of lines at once quickly leads to rubber-stamp approvals.

Key takeaways

A code review is a peer check of code changes before they are merged.
It usually happens in a pull request, with comments on specific lines.
Automated checks handle formatting and tests; humans focus on logic, design, and clarity.
Reviews catch bugs early and spread knowledge across the team.
Small changes and kind, specific feedback make reviews faster and more effective.

Example

Reviewing a branch from the command linebash

# Fetch the branch under review and see what it changes
git fetch origin
git log --oneline main..origin/feature/checkout
git diff main...origin/feature/checkout

# Check out the branch locally to run it and its tests
git switch feature/checkout
npm test

# With a hosting platform's CLI (GitHub's is shown), submit the review
gh pr review 123 --approve --body "Looks good, thanks!"
gh pr review 123 --request-changes --body "Please add a test for empty carts."

Readers ask

What should I look for in a code review?

Check that the change does what it claims, handles edge cases and errors, is readable, and fits the existing design. Also look for security issues, missing tests, and unnecessary complexity, and leave style nitpicks to automated formatters and linters.

What is the difference between a code review and a pull request?

A pull request is the mechanism for proposing that a change be merged. Code review is the activity of examining that change; it usually happens inside a pull request, but it can also be done in person or through pair programming.

Can AI replace human code review?

AI tools can quickly catch many common bugs, style issues, and security risks, and are increasingly used as a first reviewer. They don't yet reliably understand a team's goals, product context, or design trade-offs, so most teams still require human approval before merging.