The App Router introduced in Next.js fundamentally changes how we build React applications. It embraces React Server Components, nested layouts, and streaming to deliver faster and more scalable experiences.
Layouts and Nested Routing
Unlike the pages router, layouts persist between route changes. This enables shared UI like navigation and footers without re-rendering, improving both performance and UX.
"The App Router isn't just an upgrade — it's a new mental model."
Server vs Client Components
By default, components are server-rendered. Client components are opt-in, allowing you to drastically reduce JavaScript shipped to the browser.
