What Is Next.js?
Next.js is a React framework for building web applications — combining server-side rendering, static site generation, API routes, and edge middleware in one production-ready package.
Next.js is the most widely-used React framework for production web applications. It adds file-based routing, server-side rendering, and build-time static generation on top of React — along with an API layer, image optimization, and edge middleware.
Core rendering modes:
- Static Site Generation (SSG) — pages pre-rendered at build time, served from CDN
- Server-Side Rendering (SSR) — pages rendered on each request
- Incremental Static Regeneration (ISR) — static pages that re-generate on a schedule
- Server Components (App Router) — components that run on the server, send HTML to the client
App Router vs Pages Router: Next.js 13+ introduced the App Router — a new architecture based on React Server Components. Server components run on the server and send HTML, reducing client JavaScript. The Pages Router still works and is stable, but App Router is the future.
Why Next.js for SaaS products:
- API routes ship alongside the frontend in one deployment
- Server components fetch data close to the database (Vercel + Supabase)
- Built-in image optimization (WebP/AVIF conversion, lazy loading)
- Vercel deploys it automatically — push to main, live in 2 minutes
SEO benefits: Server-rendered HTML is indexed immediately by search engines. Client-only React apps require JavaScript execution before content is visible — a ranking disadvantage. Next.js eliminates this for most page types.