Tanner Linsley Reimplements React's API with 80% Less Code
Tanner Linsley, creator of TanStack, has published a deep-dive on reimplementing React’s public API from scratch while dropping most of its internal machinery. His custom implementation strips out concurrent rendering, lane-based scheduling, React DevTools, and the Flight client deserializer, with useTransition and useDeferredValue running synchronously and startTransition as a simple fn() wrapper over microtasks. The result passes all 200 React tests, achieves 2× better performance on benchmarks, and ships at 80% smaller bundle size—proving that much of React’s weight comes from implementation choices rather than its developer-facing API contracts.