Code Reviews 📚

The following is a collection of my thoughts about what makes a good code review. This is a repost from the internal Calypso blog with a few modifications made from feedback. I have also included a few tips to structure PRs in a reviewer friendly way. It’s my hope that this post will help encourage folks to get excited about code reviews.

Frame of Mind

At the start of my career, I didn’t understand why good code reviews were helpful. This was partly because I hadn’t seen a good code review yet. At best someone might have rubber stamped my change, and at worst code gatekeepers nitpicked irrelevant details in the patch leaving both parties in a foul mood.

My thoughts on reviewing changed drastically once I realized I was approaching this with the wrong frame of mind. We are rewarded by what effort we put into it, and as part of that participants must share some common understandings to avoid an unproductive review.

At Automattic, I think we already have a very strong reviewing culture. The following are a few points I personally remind myself, before starting a review.

We all share ownership of the code. It is not yours, or mine, it’s ours. Always welcome improvements and share knowledge freely.

Many programing decisions are opinions. There is often no one right answer. Discuss tradeoffs in a productive way and move on quickly. Stick with project convention for stylistic things like tabs vs spaces, even if you don’t agree with it. Changing convention can be done outside of the PR as a larger discussion with the group.

We can always learn new things. No matter how much one knows, we can always learn more. Folks can expose you to new ideas. Explaining concepts you’re familiar with can help improve your understanding of it.


Another huge part of a successful code review is good communication. We’re all nice folks at Automattic, but text communication is tricky. It is very easy to misinterpret feedback about code as something more personal. I think we’ve done a very good job at avoiding this, but here are a few techniques to lesson confusion.

  • Avoid separating code ownership. Do not assign ownership of the code with words like “my code” or “your code”. Doing so makes code reviews feel more like a personal judgement. We all share ownership of the code. Remember that the code is also a product of many constraints (time, familiarity with the codebase, etc.) and is not a personal reflection about the author. Even the best developers will produce code from time to time that has some issues to work through.
  • Assume best intent, stay positive. Avoid sarcasm and negative descriptors like “terrible” or “dumb” that may be misread.
  • Avoid demands, offer suggestions instead. “What about moving this into it’s own file?” It’s also helpful to phrase these as questions. Often times the reviewer may be missing context on why a particular suggestion will not work.
  • Authors should respond to suggestions. “Great catch! Updated in 565acae.” “We went ahead with the original approach because of timing concerns.”
  • Be explicit. “Let’s do change X because of reason Y”
  • Say if something is a blocker or optional. “Due to security concerns we should update this method before shipping.” “This is optional but I think this reads better if we move this into it’s own method.”
  • If something is confusing, ask. “What is the reasoning behind these changes?”  “I don’t understand what’s happening on this line, could you please explain?
  • Let the author know when you appreciate a change. “Thanks for taking on this task!” “I really ❤️ how this new workflow feels, I left a few notes on some things we can improve.” “This PR drops our build size by 500kb! Great work!”
  • Explain next steps, or complete the review. “I noted a few blockers I’d like to see resolved before we 🚢” “Changes here look great. 🚢 when you’re ready.”
  • Keep up momentum. If a PR looks stalled ask if anything needs to be done. This is especially important for OSS contributors. It is usually better to accept a PR that has a few issues left to work through, and fix it up later, than have the OSS person abandon the PR.

Preparing your PR to be Reviewed

If folks are always waiting for a code review it helps to have some empathy for the reviewer too!

  • Explain why. Assume reviewers have little or no context when reading the PR. Explain why we need this PR and what it does. (This is also very useful when looking at past decisions). Screenshots and gifs are appreciated when behavior is complex.
  • Add Step-By-Step Test Instructions. Can someone unfamiliar with the changes test your PR by reading the summary?
  • Keep changes small. Large changes are difficult to review and understand. Try to separate janitorial changes from PRs that change behavior.
  • Note weird things. This includes explaining any odd code workarounds, or buggy behavior. This can save some back and forth between the reviewer and author, and may also expose existing bugs.

Code Review Benefits

When done well, code reviews can help on many different levels.

  • It spreads code ownership.
  • Communicates changes across teams.
  • Serves as a sanity check to verify that requirements make sense.
  • Allows folks to find bugs though both manual testing and in code.
  • Lets all folks involved learn new things!
  • Can also serve as documentation for how something worked, and why certain decisions were made. Perhaps even for a future you!

Anyone can be a Reviewer!

The fact that code reviews work on many levels also means that reviewers don’t need to know all things about a project in order to make a meaningful contribution. Sharpening copy, manually testing, polishing design, or asking questions about confusing things is a great help.

Code Review Challenge

If this isn’t a habit for you yet, I’ll like to challenge you to try reviewing a few PRs from a different team or one that you may have felt intimidated to contribute to.

Here are a few strategies I use to pick PRs to review:

  1. Take a look at one of the oldest PRs on the needs review list. Ping the author with questions if it looks inactive.
  2. If you don’t have a lot of time, choose a tiny PR to look at. These are the fastest to review and test, and usually have the least risk of causing a regression.
  3. Choose something you’re unfamiliar with. Reviewing PRs is a great way to learn, and to keep a pulse of what’s happening on other teams. Don’t be afraid to dive into a section you’ve never looked at before. If you don’t follow, or something is unclear, ask questions! The PR author is usually happy to explain.

Have fun reviewing!