What is Nuxt.js state management with `useState`?

useState is a Nuxt composable that creates SSR-safe shared reactive state that persists across components and between server and client. Unlike Vue's ref(), useState is serialized in the server response payload and rehydrated on the client, ensuring consistent state without a flash. It takes a unique key and optional initializer: const count = useState('count', () => 0). Multiple components using the same key share the same state. For complex state management, Pinia (the official Vue state management library) integrates seamlessly with Nuxt via the @pinia/nuxt module and offers DevTools support, actions, and getters.