React Developer Tools

React Developer Tools is a browser extension that lets you see inside React applications while you're building or debugging them. When you open your browser's developer tools on a page built with React, you get a new tab that shows you the entire structure of the app's components — how they're organized, what data they hold, and how they change.

Think of it like an X-ray machine for web apps. Instead of just seeing the final HTML that appears on the page, you can inspect each React component individually, see what props and state it's holding, and watch those values update in real-time. If something's broken in your app, you can navigate through the component tree to pinpoint exactly where the problem is, rather than hunting through code blindly.

The tool works as a Chrome or Firefox extension that installs directly into your browser. Once installed, whenever you visit a site running React, you'll see a "React" tab appear in your developer tools panel. You can click on components in the tree view to highlight them on the page, search for specific components by name, and even right-click to see their source code or store them as temporary variables for testing in the console. It also highlights components with state in red so you can quickly identify which ones are holding data.

The project comes with several versions: the official Chrome and Firefox extensions (available in their respective app stores), plus experimental versions for other environments. The README notes that if the React tab doesn't show up, it usually means the extension couldn't establish communication with the page's React code — though this is rare on properly configured sites. The tool is built to be hackable, with a simpler "plain" version for development and separate directories for each browser's specific implementation.