Code review is the "last defense against brokenness." It is a critical part of the development process: no change can be putback by anyone, no matter how knowledgeable or experienced, without first being reviewed. As a version nears release, code review requirements become more strict; more reviewers may be required. The code review process can take anywhere from a few minutes to many hours, depending on the type, size, and intrusiveness of the changes being made. Normally, developers will ask others to review their changes who are familiar with the code being modified.

The purpose of code review is to find subtle and non-obvious problems with the changes being made, not to absolve the implementor of responsibility for his or her changes. Specifically, developers must conduct their own self-review and testing before requesting a formal code review.