Next.js App Router in Depth

What you’ll learn

• Model routes with layouts

  Compose nested layouts, templates, and route groups so shared UI never re-renders needlessly.

• Draw the server/client line

  Decide what runs on the server and what ships to the browser, and pass data across the boundary safely.

• Control caching

  Understand what is cached, for how long, and how to revalidate it on demand instead of guessing.

• Mutate with server actions

  Handle forms, validation, and optimistic updates without hand-writing an API layer.