# Fiber Debugger This is a debugger handy for visualizing how [Fiber](https://github.com/facebook/react/issues/6170) works internally. **It is only meant to be used by React contributors, and not by React users.** It is likely that it might get broken at some point. If it's broken, ping [Dan](https://twitter.com/dan_abramov). ### Running First, `npm run build` in React root repo folder. Then `npm install` and `npm start` in this folder. Open `http://localhost:3000` in Chrome. ### Features * Edit code that uses `ReactNoop` renderer * Visualize how relationships between fibers change over time * Current tree is displayed in green ![fiber debugger](https://d17oy1vhnax1f7.cloudfront.net/items/3R2W1H2M3a0h3p1l133r/Screen%20Recording%202016-10-21%20at%2020.41.gif?v=e4323e51)