Code review occupies a significant amount of developers’ work time and is an established practice in modern software development. Despite misaligments between users’ goals and the code review tools and processes pointed out by recent research, the code review tooling has largely stayed the same since the early 90s. Improving these tools, even slightly, has the potential for a large impact spread out over time and the large developer community.

In this paper, we use the Double Diamond design process to work together with a team of industry practitioners to find, refine, prototype, and evaluate ways to make it easier to compare refactored code blocks and find previously hard-to-see changes in them. The results show that a flexible comparison modal integrated into Gerrit could reduce the mental load of code review on refactored code. Potentially, it could also have effects on how code is written by no longer discouraging refactoring due to it complicating the review. The user interface created in this collaborative manner was also intuitive enough for all of the participants to be able to use it without any hints or instructions.