What is react-router?

React Router solves a fundamental problem for anyone building a React application: keeping track of which page or screen the user is viewing based on the URL in their browser's address bar. Without it, React apps would load all their content at once and struggle to handle navigation the way users expect from normal websites. At its core, the library connects React components to specific URLs. You tell it which component should display when someone visits /users, another component for /about, and so on. When the URL changes, either because a user clicks a link or types something in the address bar, React Router automatically swaps out which component appears on screen. The code example in the README shows how straightforward this is: you write out your route structure once, and the library handles the rest. It also extracts information from the URL itself, like user IDs in a path like /user/123, and passes that data to your components so they can load the right information. The library is useful for anyone building a multi-page React app. If you're creating a dashboard with different sections, an e-commerce site with product pages, a social media feed with user profiles, or any application where users need to navigate between different views, React Router is the standard tool. Instead of building navigation logic from scratch, you get features like lazy loading (only downloading code for pages when someone actually visits them), handling URLs with dynamic parameters, and managing the browser's back and forward buttons automatically. The README doesn't detail advanced tradeoffs, but it does emphasize that the library works in any browser where React runs, and you can use it by installing it through npm, importing it into your code, or even dropping it in as a plain script tag if you prefer not to use a build tool. The library has been around long enough to have comprehensive documentation and an active community channel on Slack for help.