Next.js is a React framework created by Vercel that provides a structured approach to building web applications. It adds file-based routing, server-side rendering, static site generation, API routes, and image optimization on top of React, eliminating the need to configure these capabilities separately.
The framework has gone through a significant architectural shift with the introduction of the App Router in version 13. React Server Components, which render on the server and send HTML to the client, change the mental model for data fetching and component composition. The transition from the Pages Router to the App Router has a learning curve, but the performance and developer experience benefits are substantial for most applications.
For full-stack React applications, Next.js provides a cohesive framework that handles both the frontend and backend in a single codebase. API routes allow you to write server-side logic without a separate backend service, which simplifies deployment and reduces infrastructure complexity for many applications.
For content-heavy sites, the static generation and incremental static regeneration features allow pages to be pre-rendered at build time or on-demand, providing fast load times without the overhead of server-side rendering on every request. The image optimization component automatically serves appropriately sized images in modern formats.
Next.js is free and open source. Deployment on Vercel is the most seamless option, with a free tier for personal projects. Self-hosting on any Node.js server is also supported.