Next.js is an open-source React framework developed by Vercel.

​Next.js Core Features & Concepts ​1. Rendering Strategies ​Next.js solves React’s primary weakness—poor search engine optimization (SEO) and slow initial load times—by offering flexible rendering options per route: ​Server Components (RSC): Rendered entirely on the server. No JavaScript bundle is sent to the client for these components, improving load speed and security. ​Server-Side Rendering (SSR): Generates fresh HTML on the server for every incoming request. Best for dynamic, user-specific data (e.g., social media feeds). ​Static Site Generation (SSG): Generates static HTML files at build time. Extremely fast and cheap to host via CDNs. Best for blogs, documentation, and landing pages. ​Incremental Static Regeneration (ISR): Allows you to update static pages in the background after deployment without rebuilding the entire app. ​2. App Router (File-Based Routing) ​Routes are defined using the file system structure inside the app/ directory instead of external routing libraries like react-router-dom: ​app/page.tsx \rightarrow / (Home page) ​app/about/page.tsx \rightarrow /about ​app/blog/[slug]/page.tsx \rightarrow /blog/my-post (Dynamic route) ​Special files inside any directory define structural behavior: ​layout.tsx: UI shared across multiple pages (e.g., sidebars, navigation bars). ​loading.tsx: Automatic fallback UI rendered while page data loads. ​error.tsx: Catch-all error boundary for unexpected component crashes. ​3. Server Actions & API Routes ​You can build full backend functionality directly inside Next.js: