Next.js is a React framework for building full-stack web applications, first released in 2016 by the company then called Zeit and now known as Vercel. Its own documentation describes it as a framework that “uses React to build user interfaces” while handling the configuration and tooling React needs, so developers can “focus on building your application instead of spending time setting up tooling.” It grew into the most widely used meta-framework in the React ecosystem, sitting on top of React rather than replacing it.
The framework’s original draw was server-side rendering. Where a plain React single-page application ships a mostly empty HTML shell and builds the page in the browser, Next.js can render React components to HTML on the server for each request, improving first-load performance and search engine visibility. Alongside server-side rendering it offers static site generation, where pages are pre-rendered to HTML at build time, and incremental static regeneration, which lets statically generated pages be refreshed after deployment.
A defining Next.js feature is file-based routing: the structure of files on disk defines the application’s URLs, removing the need to wire up a separate routing configuration. The newer App Router, built on a special directory, formalizes this with conventions such as files that define a route segment, a shared layout, an API route handler, an error boundary, and a loading state.
The App Router also brought React Server Components into mainstream use. By default, components in the App Router render on the server, which reduces the amount of JavaScript sent to the browser and allows components to access data sources directly. The remaining interactive parts of the page are then hydrated in the browser, blending server rendering with client-side interactivity.
The Next.js source code lives in the public monorepo at github.com/vercel/next.js, where its development, releases, and the evolution from the original “Pages Router” to the App Router are recorded. The project’s tight integration with Vercel’s hosting platform, plus features such as built-in image and font optimization, helped make it a default choice for new React projects.