Reverse engineer the software you pay for then rebuild only what you use

How to use one free open-source tool with Claude Code to see how an app is built, feature by feature, and keep only the parts your business needs

Free PDF, 4 pages. Updated 2026-10-27. Enter your first name and email to download it now; a copy is also emailed to you.

What's inside

Most businesses pay for software with a hundred features and use five. Reverse Engineer Anything (REA) is a free, MIT-licensed tool that plugs into Claude Code. Point it at an app or a website and it traces each feature from the click to the result, then explains how it is built, step by step. That makes it much easier to plan your own lean version of the parts you actually use.

  1. Reverse Engineer Anything (REA): the free tool from the video

    Open source under the MIT licence. Works with native apps, Electron and JavaScript apps, packages and web pages.

  2. Claude Code: the AI agent that drives it

    Claude Code runs in your terminal and calls REA as a tool, so you can ask questions in plain English, for example: how does the checkout step in this funnel save the form data?

  3. Node.js: needed to install REA

    REA installs through npm. If you can run npx in your terminal, you are ready. Static JavaScript and web analysis needs no extra engine.

Step by step

  1. Install Claude Code. Follow the official guide at anthropic.com/claude-code and sign in.
  2. Add REA. In your terminal run: npx rea-agents setup. It registers REA with your agent and installs its workflow instructions.
  3. Pick one tool you pay for. Choose software you are allowed to analyse, for example a web app your business already uses.
  4. Ask Claude to trace one feature. For example: use REA to trace what happens from clicking Submit on this form to the lead appearing in the dashboard, and explain each step.
  5. List what you actually use. Write down the five features your team uses every week. Ignore the rest.
  6. Plan your own version. Ask Claude Code to draft a plan for a simple app that does only those five things, written from scratch, then build it step by step.

How to get the guide

  1. Enter your first name and email. Takes ten seconds. No account, no password.
  2. Download the PDF. The download button appears right after you submit.
  3. Keep a copy in your inbox. We email you the guide as well, so you can find it later.

Frequently asked questions

What is Reverse Engineer Anything?

REA is a free, MIT-licensed tool that an AI agent like Claude Code can use to trace how an app or website works, from a click to the result, and explain how each feature is built.

How do I install REA?

With Node.js installed, run npx rea-agents setup in your terminal. It registers REA with your agent, such as Claude Code.

Is it legal to reverse engineer software?

It depends on the software's licence, its terms and the law where you are. Only analyse software you own or are allowed to analyse, and write your own version instead of copying code.

Why rebuild only the features I use?

Many businesses pay for large platforms but use a handful of features. A small tool that does only those can be simpler to run and easier to change.

Is the guide really free?

Yes. Enter your first name and email and you can download the PDF straight away. There is nothing to pay.

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