What is Redux?
A predictable state container that centralizes application state in a single immutable store.
Definition
Redux applies the Flux pattern with three constraints: one store holds the whole state tree, state changes only by dispatching plain-object actions, and reducers are pure functions of `(state, action) => newState`. Immutability makes time-travel debugging and action replay possible, which is what the Redux DevTools trade on. Redux Toolkit is now the official, strongly recommended way to use it—`createSlice` collapses the boilerplate of action types, creators, and reducers, and Immer lets you write apparently mutable code that produces immutable updates. Redux earned a reputation for ceremony in the pre-Toolkit era, and for many apps React's built-in state plus a lighter library like Zustand or Jotai is now the better fit; Redux remains strong where state is genuinely global and complex.