Zustand

Zustand manages React state in about 5 lines of code: no boilerplate, no providers, no reducers, no actions. Create a store, use the hook, done. Your state updates, your component re-renders, nothing else does.

MIT licensed. The API is tiny: create and useStore. That's basically it. It handles async actions naturally (just use async/await in your store), works outside React (vanilla JS), supports middleware (persist to localStorage, devtools, immer), and plays nicely with React's concurrent features.

Fully free. No paid tier. No cloud. No enterprise version. This is a community library maintained by the pmndrs collective (same folks behind Three.js React bindings). Bundle size is ~1KB gzipped. Compare that to Redux Toolkit at ~12KB. If your state needs are simple to moderate: theme, auth, UI state, API cache, Zustand is the right call.

The catch: for very large apps with complex state relationships, Redux's structure (enforced patterns, middleware chain, devtools ecosystem) can be an advantage. Zustand's simplicity means you define your own patterns, which is freedom for experienced devs and rope for beginners.