Reverse Engineer Any App With Claude
REA lets Claude take an app apart, explain how a feature works with the evidence, and then build your own version of it.
Ever wonder how WHOOP makes its orb, how Strava draws your route on the map, or how Instagram loads photos so fast?
REA (Reverse Engineer Anything) answers exactly that. It’s an open source tool that just passed 230,000 stars on GitHub. It plugs into Claude Code, reads the app itself down to the binary, explains how a feature is built with the evidence behind every step, and then builds a version of it for your own project. It runs locally, it’s MIT licensed and it’s free.
Want to build your own? The 4-Week Fitness App Challenge teaches you to build the app or AI agent you always wanted, so you can improve your training, control your own data and learn AI along the way.
How it works
Practice run. Point it at an app you’re allowed to take apart and get a map of its screens, its features and what it sends over the network.
Feature trace. Pick one feature and Claude follows it from the button you tap to the code that runs, step by step, with the evidence for each one.
Build your own. Claude writes your version from scratch in your own code and tests it.
What to point it at
The best targets are things you can see happen on your own screen, because the code that does them has to ship to you: animations and charts, maps and routes, how a feed loads so fast, and how the screens connect. Anything calculated on the company’s servers stays with them. REA shows you what the app sends and what comes back.
Websites are the easiest place to start, since they only need Chrome. Setup takes about 10 minutes with one command: npx rea-agents setup.
I wrote up the setup, what it can take apart, and all 3 prompts.
Get the full guide and all 3 prompts
Use it on apps you own or are allowed to examine. Learn how a feature works, then build your own version of the idea.
What would you take apart first? Hit reply and let me know.
Kevin
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