8 reasons your Next.js app is slow — and how to fix them

Slow Next.js applications often suffer from common performance issues, such as heavy data fetching, routing delays, oversized bundles, caching mistakes, and unoptimized images. Addressing perceived performance is crucial, as it impacts how quickly users feel the app responds, even if data loads in the background. Effective strategies include using React Suspense for loading states, optimizing hybrid rendering, and leveraging Promise.all() for parallel data fetching. Additionally, adopting client-side routing, code splitting, and dynamic imports can significantly reduce JavaScript bundle sizes, improving Time to Interactive (TTI). React hydration, caching, and image optimization are essential to enhance performance further, particularly for mobile users. The key is to focus on big wins like caching, image optimization, and code splitting, while continuously measuring performance with tools like Next.js analytics, Lighthouse CI, and real user monitoring to ensure a smooth user experience.