Seven Common Next.js App Router Mistakes Developers Should Avoid

Next.js App Router introduces a server-first architecture that requires developers to rethink common patterns from earlier React development. Frequent mistakes include defaulting to client-side data fetching with useEffect when server-side fetching would reduce JavaScript and improve load times. Developers also tend to mark entire pages as Client Components unnecessarily, when only small interactive elements need to run on the client. Other pitfalls involve bloated Server Actions containing business logic, oversized client bundles from heavy libraries, and placing context providers too broadly in layout files. The core principle recommended is to default to server rendering and shift to the client only when interactivity genuinely requires it.