Code review: best practices, checklist and AI tools

Code review is the practice of having one or more developers examine a change to the code before it is merged, to find errors, improve quality and share knowledge. It is one of the cheapest ways to catch defects early, and it also protects security and client satisfaction.

TL;DR

• Code review means a second pair of eyes on every change before it reaches production.
• The four business benefits are better code quality, more collaboration, lower risk and happier clients.
• Effective reviews rest on clear guidelines, automated tools and specific, actionable feedback.
• A short checklist keeps reviews consistent: correctness, security, tests, readability and scope.
• AI code review speeds up the first pass but cannot judge intent, so a human still decides.
• When a whole codebase needs checking, a code audit extends the same logic beyond single changes.

What is code review and why does it matter for a business?

Code review is a step in the software development process where developers inspect each other's code to find errors, improve quality and confirm that the software meets client requirements. It matters to a business because defects found before release cost far less to fix than defects found by customers in production.

The practice has four main benefits, covered in the sections below. In a competitive market, high-quality software is critical for success, and review is one of the most reliable ways to get there. For deeper checks across a whole system, see our code audit service.

What are the benefits of code review?

Code review improves code quality, increases collaboration, reduces risk and raises client satisfaction. Each benefit comes from catching problems and sharing knowledge while a change is still small. The earlier an issue is found, the cheaper it is to fix, and the less likely it is to reach your users.

• Improved code quality: review identifies errors, redundancies and other issues before they cause problems in production. Finding and fixing them early avoids costly bugs and keeps the software running smoothly.
• Increased collaboration: team members share knowledge, learn from one another and develop new skills. This improves team cohesion and productivity, and leads to better development outcomes.
• Reduced risk: review helps mitigate data breaches and other security issues by spotting vulnerabilities and confirming that proper security protocols are in place.
• Increased client satisfaction: software that meets client requirements and expectations helps build long-term relationships.

How does an effective code review process work?

An effective code review process starts with a small change, an author who explains it, and a reviewer who checks it against agreed guidelines. The reviewer gives specific feedback, the author fixes or discusses it, and the change merges only when it clearly improves the codebase. Automation handles the mechanical checks beforehand.

Google's public engineering practices state the same standard: a reviewer should approve a change once it definitely improves the overall health of the code, even if it is not perfect. That keeps reviews fast without lowering quality.

Three strategies make the process work in practice:

• Establish clear guidelines: agree coding standards, error management and documentation rules so everyone is on the same page.
• Use automated tools: linters, static analysis and automated review tools reduce manual effort and can find issues that are hard for humans to see.
• Provide specific feedback: point to the line, explain the issue and suggest how to address it, so developers understand what to change and why.

What should a code review checklist include?

A useful code review checklist covers correctness, security, tests, readability, performance and scope. It turns reviewer judgement into a repeatable routine, so two reviewers reach similar conclusions on the same change. Keep it short enough to apply on every review, and adapt it to your stack and risk level.

1. Correctness: does the change do what the ticket asks, including edge cases and error paths?
2. Security: is input validated, are secrets kept out of the code, and are access rules respected?
3. Tests: are new behaviours covered, and do existing tests still pass?
4. Readability: are names clear, functions focused and comments useful?
5. Performance: does the change avoid obvious waste, such as repeated queries inside loops?
6. Scope: is the change small and limited to one purpose, so it can be reviewed properly?
7. Documentation: are public interfaces, configuration and decisions recorded where the team will find them?

Review and testing work together. Our guide to why QA testing is crucial explains how tests catch what a reviewer cannot see by reading.

Can AI code review replace human reviewers?

No, AI code review cannot replace human reviewers, but it is a useful first pass. Automated assistants flag style problems, likely bugs and known vulnerability patterns quickly. They do not know your business intent, your architecture or your risk appetite, so a person must still decide whether a change should merge.

AI-generated code makes this more important, not less, because it can look correct while hiding subtle flaws. Treat AI suggestions like any other contribution: review them against the same checklist. Our article on how AI is changing app development covers the tools and the risks in more detail.

How do you measure whether code review is working?

You measure code review by watching a few simple indicators over time: how long changes wait for a first review, how many defects escape to production, and how often reviewed changes are reworked afterwards. These show whether review is catching problems without becoming a bottleneck for delivery.

Choose a baseline before you change the process, and compare after a few sprints. Avoid targets that reward speed alone, because rushed approvals defeat the purpose. If you find that quality problems persist despite reviews, a wider software audit can show where the real causes lie.

How can WWG help with code review?

WWG's team of developers can help you identify and fix issues in your code, improve quality and make sure your software meets client requirements. This can mean setting up a review process with your team, or reviewing an existing codebase through the code audit service, with findings you can act on.

Review is also a good moment to look at the bigger picture. A thorough audit looks at architecture, dependencies and security together, which a review of single changes cannot do.

Want a second opinion on your code? Talk to a WWG engineer about reviewing your codebase.

Sources

• Code Review Developer Guide, Google Engineering Practices
• The Standard of Code Review, Google Engineering Practices