What is Redux Toolkit?

Redux Toolkit (RTK) is the official, opinionated toolset for Redux development, created to address Redux's historical boilerplate problems. It is now the standard way to write Redux. Key utilities: configureStore(): simplified store setup with good defaults (DevTools, Thunk middleware). createSlice(): generates action creators and action types from reducer functions: const counterSlice = createSlice({ name: "counter", initialState: 0, reducers: { increment: state => state + 1, addAmount: (state, action) => state + action.payload } }). createAsyncThunk(): handle async operations with auto-generated pending/fulfilled/rejected actions. createEntityAdapter(): normalized state management for collections of entities. RTK Query: powerful data fetching and caching solution built into RTK. Benefits: eliminates ~75% of Redux boilerplate, enforces best practices, includes Immer for immutable updates, and provides excellent TypeScript support. All new Redux apps should use RTK — writing "hand-written" Redux is no longer recommended.