Next.js 15.3 brings key improvements focused on performance and developer experience. It introduces alpha support for using Turbopack in production builds, delivering much faster build times—especially on machines with many CPU cores. There’s also experimental community support for Rspack as an alternative bundler. New navigation hooks like onNavigate and useLinkStatus offer better routing control, and a new client instrumentation hook makes it easier to integrate monitoring tools. TypeScript plugin updates further improve performance in large projects.