Next.js v15 is here, and it's a major update that addresses some long-standing issues. One notable change is Partial Fallback Prerendering (PFPR), which allows for faster rendering by sending pre-built parts to the client while loading dynamic elements. This feature will be especially useful for complex applications.

Another significant improvement is instrumentation, which has been marked as a stable API. This means developers can now hook into the lifecycle of the Next.js server and gain insights into their application's performance. The instrumentation file supports various hooks, including register and onRequestError, making it easier to integrate with observability libraries like OpenTelemetry or datadog.

The introduction of interceptors, also known as route-level middleware, is another major development. Interceptors can be used for tasks like redirecting requests or handling errors, and they will work seamlessly on Vercel's CDN level.

Source: https://dev.to/vordgi/nextjs-v15-reflecting-on-mistakes-3jh3