React Compiler is a build-time optimization tool that automatically memoizes React components, values, and function references — eliminating the need for manual use of React.memo, useMemo, and useCallback. It became stable in October 2025 and integrates with Vite, Next.js, and Rsbuild via a Babel plugin. The compiler memoizes at a more granular level than manual approaches, caching individual JSX elements independently. Production results show meaningful gains: Instagram saw 3% average improvement, Sanity Studio achieved 20-30% better rendering, and Wakelet reported 15% INP improvement. Key drawbacks include misleading Memo badges in DevTools, library compatibility issues with hooks that return unstable references (TanStack Query, Material UI, React Router), harder debugging due to black-box behavior, and challenges adopting it in legacy codebases. It works best for new projects following the Rules of React with minimal third-party library dependencies.
