What is Redux, and why is it used in React applications?

Updated Feb 20, 2026

Short answer

Redux is a state management library used with React to manage shared application data in a predictable way. It stores state in a central place and updates it through clear actions and reducers, making complex data flows easier to understand and debug.

Deep explanation

React components usually manage their own local state with useState, but larger applications often have data that many components need to access. Examples include logged-in user information, shopping cart items, application settings, or permissions.

Redux solves this by providing a single source of truth: a centralized store that holds shared state. Components do not directly modify that state. Instead, they describe what happened by dispatching actions, and reducers decide how the state should change.

How Redux works

The core Redux flow has three important pieces:

Store: Holds the complete application state.
Action: A plain JavaScript object describing an event, usually with a type field.
Reducer: A pure function that receives the current state and an action, then returns the next state.

The flow looks like this:

Rendering diagram…

For example, when a user clicks "Add to Cart":

The component dispatches an addItem action.
A reducer handles that action.
The store updates the cart state.
Components reading the cart receive the new data.

A simplified reducer might look like:

cartReducer.js

JavaScript

1const initialState = {
2  items: []
3};
4
5function cartReducer(state = initialState, action) {
6  switch (action.type) {
7    case "cart/addItem":
8      return {
9        ...state,
10        items: [...state.items, action.payload]
11      };
12
13    default:
14      return state;
15  }
16}

Why use Redux with React?

React already has state management through hooks, so Redux is not required for every application. It becomes useful when state is:

Shared across many unrelated components.
Frequently updated from different parts of the application.
Important enough that debugging changes is difficult.
Needed across routes or large feature areas.

Redux also improves predictability because state changes follow a strict pattern. Developers can inspect actions, replay changes, and track how data moved through the application using tools like Redux DevTools.

Redux is most valuable when the problem is not storing state, but controlling how shared state changes over time.

Redux trade-offs

Approach	Best for	Trade-off
`useState` / `useReducer`	Local component state	Can become difficult for widely shared data
Context API	Simple global values	Can become harder to organize for complex updates
Redux	Large apps with complex shared state	Adds concepts and some boilerplate
Server-state libraries	API data and caching	Not a replacement for all client state

Modern Redux usage commonly relies on @reduxjs/toolkit, which reduces boilerplate with helpers like createSlice. The goal is still the same: make state changes explicit, predictable, and easier to maintain.

⚡ Use Redux when state complexity grows, not simply because an application uses React.

Real-world example

Imagine an e-commerce website where a user adds products to a cart. The cart icon in the header, checkout page, and product page all need the same cart data.

Without a shared store, developers may pass data through many component layers or duplicate logic. With Redux, all components can read from the same store and update it through actions.

cartSlice.js

JavaScript

1const cartSlice = createSlice({
2  name: "cart",
3  initialState: [],
4  reducers: {
5    addItem: (state, action) => {
6      state.push(action.payload);
7    }
8  }
9});

A product button can dispatch addItem, and every connected component automatically receives the updated cart state.

Common mistakes

* **Using Redux everywhere** - Adding Redux for tiny local state increases complexity
use component state when data does not need sharing.
* **Mutating state directly** - Changing objects manually inside reducers can create bugs
return new state or use Redux Toolkit patterns.
* **Storing server data unnecessarily** - API data often needs caching tools
Redux is not always the best database for remote state.
* **Skipping state design** - A poorly structured store becomes difficult to maintain
organize state around features and usage patterns.

Follow-up questions

Why does Redux use reducers instead of letting components update state directly?
What is the difference between Redux and React Context?
What is Redux Toolkit and why is it recommended?
When should you avoid using Redux?