app-router

Dynamic routes in the Next.js App Router are structured using bracket notation like [slug] within the app directory to create page components that fetch data and handle specific path segments. You can also use catch-all and optional catch-all segments for more complex routing hierarchies.

In Next.js, loading.tsx creates loading states for immediate UI feedback during route rendering, while error.tsx establishes error boundaries to catch and handle unexpected runtime errors gracefully within specific route segments.

Yes, a root layout is required for your Next.js app directory. It must be defined in the top-level layout file and include the required html and body tags to ensure proper rendering and structure for all nested route layouts.

Parallel routes in Next.js allow you to render multiple pages simultaneously within a single layout using slots, while intercepting routes load routes within the current layout context, commonly used for modals while preserving the background layout state.

To handle not-found pages in the Next.js App Router, you add a not-found.tsx file to your route segment. This file renders a custom UI when the notFound function is called or when a requested route segment cannot be matched.

Yes, you can use route groups denoted by parentheses to organize routes without affecting the URL path, and private folders prefixed with an underscore to collocate internal files safely outside of the Next.js routing hierarchy.