What is Valtio?

Valtio is a simple, proxy-based state management library for React and vanilla JavaScript. Created by Daishi Kato (also the creator of Jotai and Zustand). Create state: import { proxy, useSnapshot } from 'valtio'; const state = proxy({ count: 0, text: '' });. Mutate directly (outside React): state.count++; state.text = "hello". In React components, use useSnapshot for reactivity: const snap = useSnapshot(state); <div>{snap.count}</div>. The snapshot is a read-only version of the proxy — mutations must happen on state, not snap. Deep reactivity: nested objects are automatically proxied: state.user.name = "Alice" triggers re-renders. Derived state: const derived = derive({ doubled: get => get(state).count * 2 }). Use cases: Valtio is excellent for React apps that want MobX-like mutable state without class syntax. Its proxy-based approach feels natural coming from Vue's reactivity. The main trade-off: mutations are implicit, making debugging harder than Redux's explicit action model.