nextjs-app-development

App Router enables server-first rendering with Server Components by default. Create pages under the app/ directory, use Server Components for data fetching and logic, add Client Components with 'use client' where interactivity is needed, and leverage Server Actions for mutations. This architecture reduces client-side JavaScript and improves performance.

SSR (Server-Side Rendering) generates pages on request, SSG (Static Generation) builds pages at build time for fast delivery, and ISR (Incremental Static Regeneration) revalidates static pages on demand without full rebuilds. Choose based on content frequency: SSG for static content, ISR for occasionally-updated data, SSR for dynamic user-specific pages.

Use bracket notation in file names—app/posts/[id]/page.tsx—to create dynamic segments. Access params via typed props in Server Components; Next.js passes params and searchParams as strongly-typed objects. This enables clean URLs and SEO-friendly routing without manual query parsing.

Yes, Server Actions let you define server-side functions directly in Server Components or separate files, then call them from forms or Client Components. They handle mutations securely on the server, support revalidation to update cached data, and eliminate the need for separate API routes for simple backend operations.

App Router uses Route Handlers (app/api/route.ts) as the modern approach to create backend endpoints. Server Components can fetch from Route Handlers or external APIs directly, while Client Components use fetch() or libraries. This keeps API logic colocated with your frontend and supports TypeScript end-to-end.

No, both routers work simultaneously in the same project during migration. App Router is the recommended approach for new projects; Pages Router remains supported for existing apps. Gradual adoption lets you adopt App Router features incrementally without rewriting your entire codebase.