The client-side rendering problem
React applications in 2016 run entirely in the browser: the server sends an empty HTML page, the browser downloads the JavaScript bundle, executes it, and only then does the user see content. This approach — client-side rendering (CSR) — has concrete consequences: search engines struggle to index JavaScript-generated content, time-to-first-content is high on slow connections, and configuring webpack, Babel and a server for server-side rendering requires significant effort. Next.js, released by Zeit (later renamed Vercel) under the leadership of Guillermo Rauch, proposes an integrated solution.
Server-side rendering and getInitialProps
Next.js brings server-side rendering (SSR) to React without requiring manual configuration. Every page is rendered on the server on the first request: the browser receives complete HTML with content already visible, then React “hydrates” the page to make it interactive. The mechanism is transparent to the developer.
The getInitialProps function is the connection point between server and page: it runs on the server during the first request and in the browser during client-side navigation, allowing data to be loaded from APIs or databases before the page is rendered. The developer writes the logic once and the framework decides where to execute it.
Filesystem routing and code splitting
Filesystem-based routing eliminates the need to configure a router: every file in the pages/ folder automatically becomes a route. A file pages/about.js maps to the URL /about, a file pages/blog/[id].js handles dynamic routes. Convention replaces configuration.
Automatic code splitting divides the JavaScript bundle per page: when the user navigates to /about, the browser downloads only the code needed for that page, not the entire application. The result is a loading time proportional to the complexity of the individual page, not the whole application.
Static export
Next.js also supports static export: the entire application can be generated as static HTML files during the build, ready to be served from any CDN without a Node.js server. The framework is released under the MIT licence and positions itself as the standard for React applications that need SSR, SEO and first-load performance.
Link: nextjs.org