It can be difficult to get a team started on code reviews, especially an established team without an established culture of reviews. Developers can be very defensive about their code, and often don’t see the value in code reviews. But the value is undeniable, and good developers will come to appreciate code reviews once they get used to them. Why?

• Reviews reduce defects. This is the primary purpose of reviews, and they’re very effective.
• Reviewing code builds familiarity for the reviewer. The reviewer is exposed to code they might not have worked with before, giving them a broader base of knowledge in their own development work.
• Reviewing code improves developers ability to self-review. The more code you review, the better you get at reviewing code. The better you are at reviewing code, the better you can review your own code before you commit it. The better reviewed code is before it’s committed, the fewer defects are found in peer review, and the faster peer reviews are.
• Expecting code to be reviewed encourages developers to self-review. Knowing that someone else is going to go over your changes after you submit them encourages you to self-review to save yourself the embarrassment, however slight, of a failed peer review.
• Peer review improves consistency. When developers submit code without anyone else looking at it, they tend to follow their own styles and practices. As they review more of each others’ code, they will naturally tend to converge on a fairly similar set of styles and practices.
• Peer review helps to breed a sense of collective ownership. After peer review, code is no longer “his code” or “her code” or “their code” it’s “our code”.
• In situations where everyone is an architect – which I strongly support – peer review is even more critical. Collective design is only collective if everyone is looking over each other’s shoulders, seeing how problems are being solved, and suggesting possible alternative solutions. It really helps close the gap between a group of individuals and a true development team.

Countless tools exist for performing code reviews; the review handling built into pull requests in Atlassian’s Bitbucket and Stash is excellent, though there are many solutions, from simple things like adding a review step to your ticket workflow and putting review comments in the ticket, to using a dedicated review tool like Crucible or Reviewboard.