Code Review – Definition, Use Cases and Best Practices at a Glance
The systematic review of source code by other developers to find defects, ensure quality and share knowledge within the team.
What is Code Review? Definition, Benefits & Best Practices
Code reviews are among the most effective ways to improve software quality. Studies show that code reviews find up to 60% of defects before deployment – far more than automated tests alone. But they do more than find bugs: they spread knowledge, enforce consistent standards and prevent critical system knowledge from sitting with single developers. In modern teams they are a standard part of the workflow.
This glossary entry for Code Review gives you a clear Definition, practical Use Cases and Best Practices at a glance – with examples, pros and cons, and FAQs.
What is Code Review?
- Code Review – The systematic review of source code by other developers to find defects, ensure quality and share knowledge within the team.
Code review is the structured process in which one or more developers review code written by a colleague before it is merged into the main branch. The review covers correctness (does the code do the right thing?), clarity (is it readable and maintainable?), performance (obvious bottlenecks?), security (e.g. SQL injection, XSS?) and adherence to team conventions.
Reviews typically happen via pull requests (GitHub) or merge requests (GitLab), and can be synchronous (pair programming) or asynchronous (written comments).
How does Code Review work?
A developer creates a feature branch, implements changes and opens a pull request. Automated checks (linter, tests, security scans) run first. Then one or more reviewers look at the code: they comment, ask questions, suggest improvements or approve. The author responds, makes changes and marks comments as resolved. After approval the code is merged.
Good teams define review guidelines: max PR size (e.g. under 400 lines), turnaround time (e.g. under 24 hours) and clear approval criteria.
Practical Examples
A senior developer finds a race condition in a multi-threaded service during review that automated tests would not have caught – a potential production incident is avoided.
A new team member learns the project’s architecture through reviews: each PR comment explains design decisions and conventions.
A team uses GitHub Code Owners to assign PRs to the right reviewers based on changed files.
A DevOps engineer reviews infrastructure code (Terraform, Docker) and prevents a misconfiguration that would have exposed the production database.
An open-source project uses multi-stage reviews: one maintainer for architecture, another for code quality and tests.
Typical Use Cases
Quality assurance: Find defects, security issues and design problems before deployment
Knowledge sharing: Use reviews so the whole team understands the system
Onboarding: New developers learn the codebase and conventions through reviews
Compliance: Four-eyes principle for regulated industries (finance, healthcare, automotive)
Architecture quality: Ensure new features fit the existing architecture and avoid tech debt
Advantages and Disadvantages
Advantages
- Early defect detection: Bugs are found before they reach production
- Knowledge distribution: No single point of knowledge – the team can maintain the code
- Higher quality: Consistent standards, readability and thought-through design
- Mentoring: Juniors learn best practices in the flow of work
- Security: Extra layer against critical mistakes
Disadvantages
- Time cost: Reviews take developer time – poor process can make them a bottleneck
- Blocked developers: Waiting for review can interrupt flow
- Subjectivity: Without clear guidelines, style debates (bikeshedding) can drag on
- Uneven load: Experienced developers can be overloaded with reviews
Frequently Asked Questions about Code Review
How large should a pull request be?
Ideally under 400 changed lines. Studies show review quality drops sharply beyond that – reviewers find fewer issues and approve more superficially. Large features should be split into several smaller, logical PRs. Each PR should have a clear description, context and if needed screenshots or test instructions.
Who should perform code reviews?
Ideally at least one developer familiar with the affected code, plus optional specialists (e.g. security for auth code). Juniors should review too – they ask useful questions and learn. GitHub Code Owners can auto-assign by file path.
How does code review differ from pair programming?
Pair programming is synchronous: two people work on the same code at once. Code review is asynchronous: someone reviews code that is already written. Pair programming catches issues in real time and fosters deep knowledge sharing but is more resource-intensive. Many teams use both: pairing for complex features, reviews for normal flow.
Direct next steps
If you want to apply or evaluate Code Review in a real project, start with these transactional pages:
Code Review in the Context of Modern IT Projects
This page provides a concise definition of Code Review, practical use cases and best practices at a glance — everything you need to evaluate the technology for your next project. Code Review falls within the domain of Methods and plays a significant role across a wide range of IT projects. When evaluating whether Code Review is the right fit, organizations should look beyond the technical merits and consider factors such as existing team expertise, current infrastructure, long-term maintainability, and total cost of ownership.
Drawing on our experience from over 250 software projects, we have found that correctly positioning a technology or methodology within the broader project context often matters more than its isolated strengths.
At Groenewold IT Solutions, we have worked with Code Review across multiple client engagements and understand both its advantages and the typical challenges that arise during adoption. If you are unsure whether Code Review suits your particular requirements, we are happy to provide an honest, no-obligation assessment. We analyze your specific situation and recommend the approach that delivers the most value — even if that means suggesting an alternative solution.
For more terms in the area of Methods and related topics, see our IT Glossary. For concrete applications, costs, and processes we recommend our service pages and topic pages — there you will find many of the concepts explained here put into practice.
Related Terms
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