Code Review Best Practices
The complete guide to effective code reviews. Learn best practices for authors, reviewers, and teams. Includes downloadable checklist.
Why Code Reviews Matter
The data behind effective code reviews
Code reviews are one of the most effective practices in software engineering. Research shows that teams practicing thorough code reviews find 60% of defects before production, improve code maintainability, and accelerate knowledge sharing across the team.
60%
Defect Reduction
Bugs caught before production
3x
Knowledge Sharing
Faster onboarding and expertise spread
30%
Better Maintainability
Cleaner code that's easier to modify
Beyond Bug Finding
While catching bugs is important, effective code reviews provide much more value:
• Knowledge sharing: Spread expertise across the team
• Mentorship: Help junior developers learn from seniors
• Consistency: Maintain coding standards and patterns
• Collaboration: Build team cohesion and shared ownership
• Quality culture: Reinforce that quality matters
The Code Review Process
Step-by-step workflow
Step 1: Author Prepares the PR
• Write clear, focused changes (keep under 400 lines)
• Write comprehensive PR description
• Self-review the code before requesting review
• Ensure tests pass and code is linted
• Add screenshots/videos for UI changes
Step 2: Request Review
• Assign appropriate reviewers (2-3 maximum)
• Add labels for priority/type
• Link related issues or tickets
• Set expectations for urgency
Step 3: Reviewer Examines Code
• Read PR description and context
• Review code systematically (architecture → implementation → tests)
• Leave specific, actionable feedback
• Approve, request changes, or comment
• Complete within 24 hours (industry standard)
Step 4: Author Addresses Feedback
• Respond to each comment
• Make requested changes
• Explain if you disagree with feedback
• Re-request review after changes
Step 5: Merge and Close
• Ensure all reviewers have approved
• Verify CI/CD checks pass
• Squash or merge commits appropriately
• Delete the branch after merge
Best Practices for Authors
Make your PRs easy to review
Write Clear PR Descriptions
A good PR description should answer:
• What changed?
• Why was this change needed?
• How does it work?
• How to test the changes?
• Screenshots/videos for UI changes
Keep PRs Small
Research shows optimal PR size:
• Under 400 lines: Ideal size for thorough review
• 400-800 lines: Acceptable but harder to review
• Over 800 lines: Too large, split into multiple PRs
Small PRs get reviewed 60% faster and have 40% fewer defects than large PRs.
Self-Review First
Before requesting review:
• Read through your own code
• Catch obvious mistakes and typos
• Add comments for complex logic
• Ensure tests cover edge cases
• Check that code follows team conventions
Respond Promptly to Feedback
Good feedback etiquette:
• Respond to every comment
• Say "done" or explain why you didn't make the change
• Don't take feedback personally
• Ask questions if feedback is unclear
• Re-request review after addressing comments
Best Practices for Reviewers
Give helpful, constructive feedback
Review Within 24 Hours
Industry standard is to complete first review within 24 hours of PR creation. This is the #1 factor in PR cycle time. Long review delays kill momentum and context.
If you can't review within 24 hours, reassign or notify the author immediately.
Focus on What Matters
Prioritize feedback in this order:
1. Correctness: Does it work? Any bugs?
2. Architecture: Is the approach sound?
3. Readability: Can others understand it?
4. Tests: Are edge cases covered?
5. Style: Only if not enforced by linter
Be Constructive, Not Critical
Frame feedback positively:
❌ "This is wrong."
✅ "This might not handle the case when X is null. Consider adding a check?"
❌ "Why didn't you use a map here?"
✅ "Using a map here would improve performance for large datasets. What do you think?"
Distinguish Must-Fix from Nice-to-Have
Use clear prefixes:
[blocking] Must be fixed before merge
[nit] Minor suggestion, not blocking
[question] Asking for clarification
[praise] Highlighting good code
Team-Level Best Practices
Build a strong code review culture
Set Clear SLAs
Document and enforce review timelines:
• First review within 24 hours
• Follow-up reviews within 8 hours
• Small PRs (<200 lines) within 4 hours
• Hotfixes within 2 hours
Balance Reviewer Workload
Prevent senior engineers from becoming bottlenecks. Track review distribution monthly. If one person reviews over 50% of PRs, redistribute. Use automated assignment to balance load.
Track Review Metrics
Monitor these key metrics:
• Median PR cycle time
• Time to first review
• Review distribution by person
• PRs waiting over 48 hours
Build Psychological Safety
Code reviews should feel collaborative, not adversarial. Celebrate good code. Make feedback about the code, not the person. Never use reviews for performance evaluation. Blameless culture enables honest feedback.
Code Review Checklist
Essential items to check in every review
Functionality & Correctness
☐ Code does what it's supposed to do
☐ Edge cases are handled
☐ Error handling is appropriate
☐ No obvious bugs or logic errors
☐ Performance is acceptable
Architecture & Design
☐ Follows existing patterns and conventions
☐ Code is in the right place
☐ Abstractions are appropriate (not over-engineered)
☐ Dependencies are reasonable
☐ Future maintainability considered
Readability & Maintainability
☐ Code is easy to understand
☐ Variable and function names are clear
☐ Comments explain "why," not "what"
☐ Complex logic is documented
☐ Code follows team style guide
Testing
☐ Tests cover happy path
☐ Tests cover edge cases and errors
☐ Tests are maintainable
☐ All tests pass
☐ Test coverage is adequate
Security & Privacy
☐ No sensitive data in logs or errors
☐ Input validation is present
☐ No SQL injection risks
☐ Authentication/authorization is correct
☐ No secrets committed to repo
Common Code Review Mistakes
Avoid these pitfalls
Mistake #1: Reviewing Only for Style
Nitpicking indentation and naming while missing architectural issues. Use linters to enforce style automatically. Focus reviews on logic, correctness, and design decisions.
Mistake #2: Rubber Stamping Large PRs
Approving 1000-line PRs without thorough review because they're too big to review properly. Large PRs should be rejected and split into smaller ones. Don't reward bad PR hygiene.
Mistake #3: Taking Days to Review
Slow reviews kill momentum and force authors to context-switch. If you can't review within 24 hours, reassign immediately. Fast feedback loops are critical for team velocity.
Mistake #4: Being Vague
Comments like "this could be better" or "refactor this" without specifics. Always explain what to change and why. Better yet, suggest the specific improvement.
Mistake #5: Perfectionism
Blocking PRs over minor improvements that could be done later. Perfect is the enemy of good. If the code works, is tested, and is maintainable, ship it. Don't let perfectionism slow delivery.
Related Resources
Automate Code Reviews
Cut PR time by 60% with automation
Best Code Review Tools
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PR Management
Stop chasing PRs manually
Tools to Improve Your Code Review Process
Automation and support tools
TeamOnTrack
Automated code review workflow management. Smart reviewer assignment, stuck PR detection, and automated reminders. Reduces PR cycle time by 60%.
Try FreeLinters & Static Analysis
ESLint, Prettier, SonarQube, etc. Automate style and common bug detection so reviewers can focus on architecture and logic.
CI/CD Integration
GitHub Actions, CircleCI, etc. Automated tests, builds, and checks before human review. Catch obvious issues automatically.