Next.js is an open-source React framework used to build fast, scalable, and SEO-friendly web applications. Developed by Vercel, it provides powerful features such as server-side rendering (SSR), static site generation (SSG), client-side rendering, API routes, and automatic code splitting to improve performance and user experience. Next.js also includes built-in support for routing, image optimization, TypeScript, and modern web development practices, making it easier to create high-performance websites and applications. It is widely used for developing e-commerce platforms, business websites, dashboards, blogs, and enterprise applications. With its flexibility, speed, and strong developer ecosystem, Next.js has become one of the most popular frameworks for modern React-based web development.