100 Must-Know React Interview Questions and Answers 2025

React Basics

1.
What is React and why is it used?
2.
How is React different from Angular or Vue?
3.
What is a React component?
4.
How do you create a component in React?
5.
What is JSX and why do we use it in React?
6.
Can you explain the virtual DOM in React?
7.
What are the differences between a class component and a functional component?
8.
How do you handle events in React?
9.
What are state and props in React?
10.
How do you pass data between components in React?

React State Management

11.
What is a stateful component?
12.
Can you explain how useState works?
13.
How do you update the state of a parent component from a child component?
14.
What is lifting state up in React?
15.
When do you use Redux or Context API for state management?

React Lifecycle & Hooks

16.
Explain the lifecycle methods of a React class component.
17.
How do hooks work in React?
18.
Can you describe the useEffect hook and its purpose?
19.
How do you fetch data with hooks in React?
20.
What rules do you have to follow when using hooks?

Component Communication

21.
How do props work in React?
22.
What is prop drilling and how can you avoid it?
23.
Explain the Context API and its use cases.
24.
How do you use render props?
25.
What is the children prop?

Performance Optimization

26.
Why is performance optimization important in React?
27.
What is React.memo and when would you use it?
28.
How does PureComponent differ from Component in React?
29.
Can you explain the concept of reconciliation in React?
30.
How can you prevent unnecessary re-renders in React?

Styling in React

31.
How do you apply styles in a React application?
32.
What is CSS-in-JS and how do you implement it in React?
33.
Can you describe how Styled-Components work?
34.
What are the advantages of using Sass or LESS in a React project?
35.
How do you use inline styles in React?

React Routing

36.
What is React Router?
37.
How do you create dynamic routes in React?
38.
How would you pass data to routes in React Router v5+?
39.
How do you programmatically navigate using React Router?
40.
What are route guards and how can you implement them in React?

React Patterns

41.
What are higher-order components (HOCs)?
42.
Explain the container/presenter (smart/dumb) component pattern.
43.
How would you implement a compound component pattern in React?
44.
Explain the use of custom hooks in React.
45.
What is a render prop pattern?

Form Handling

46.
How do you handle forms in React?
47.
What is controlled and uncontrolled components?
48.
How do you validate forms in React?
49.
What is Formik and how is it used in React forms?
50.
How do you handle file uploads in React?

React with TypeScript

51.
What are the benefits of using TypeScript with React?
52.
How do you define types for props and state in TypeScript with React?
53.
Explain how to use interfaces with React components and TypeScript.
54.
How do TypeScript generics enhance react components?

Testing in React

55.
Why is testing important in React?
56.
What are some common testing libraries for React?
57.
How do you test a React component with Jest?
58.
Can you explain the difference between shallow rendering and mount rendering in Enzyme?
59.
What is react-testing-library and how is it different from Enzyme?

Advanced React Topics

60.
What are React fragments and why are they useful?
61.
What is React portal and when would you use it?
62.
How does error boundary work in React?
63.
What is server-side rendering and how is it done with React?
64.
Can you explain the concept of suspense and lazy loading in React?

React and SEO

65.
How does React affect SEO?
66.
What strategies would you use to make a React application SEO-friendly?
67.
How can server-side rendering improve SEO with React applications?

React Native

68.
What is React Native and how is it different from React?
69.
How do you bridge native modules in React Native?
70.
Can you describe the layout system in React Native?

State Management Libraries & GraphQL

71.
What is Apollo Client and how does it integrate with React?
72.
How do you manage local state in Apollo Client?
73.
What is Redux and how does it contrast with the Context API?
74.
Can you detail the Redux workflow?
75.
How do you handle side effects in Redux applications?

React Development Environment & Tooling

76.
How do you set up a React project from scratch?
77.
What is Babel and why do we use it with React?
78.
What is Webpack and what role does it play in React development?
79.
How does hot module replacement work in React?
80.
What are the features of create-react-app and how do you eject from it?

Integrations and API Handling

81.
How do you handle API calls in React?
82.
What is Axios and how is it used over fetch in React applications?
83.
How would you handle WebSocket connections in a React application?
84.
What are some strategies used to connect a React front end to a backend server?

Deployment and Optimization

85.
How would you deploy a React application?
86.
How do you optimize the performance of a React application for production?
87.
What are service workers and how can they benefit a React application?
88.
How do you configure HTTPS in a React app?

Accessibility in React

89.
Why is accessibility important in web development?
90.
How can you make a React application accessible?
91.
What is ARIA and how it is used in React?

Internationalization and Localization

92.
What is internationalization (i18n) in React?
93.
How do you implement localization (l10n) in a React app?

React Code Structure & Best Practices

94.
How do you structure large React applications?
95.
What are some best practices when writing React code?
96.
How do you ensure code quality and maintainability in a React project?

React and Git Workflows

97.
How do you manage feature branches in React development with Git?
98.
What are your strategies for resolving merge conflicts in React projects?

React Interviews Problem Solving and Scenarios

99.
How would you handle a feature request or bug report in an ongoing React project?
100.
Describe your process for optimizing a component that has complex state logic and several child components.

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100 React interview questions

What is React and why is it used?

How is React different from Angular or Vue?

What is a React component?

How do you create a component in React?

What is JSX and why do we use it in React?

Can you explain the virtual DOM in React?

What are the differences between a class component and a functional component?

How do you handle events in React?

What are state and props in React?

How do you pass data between components in React?

What is a stateful component?

Can you explain how useState works?

How do you update the state of a parent component from a child component?

What is lifting state up in React?

When do you use Redux or Context API for state management?

Explain the lifecycle methods of a React class component.

How do hooks work in React?

Can you describe the useEffect hook and its purpose?

How do you fetch data with hooks in React?

What rules do you have to follow when using hooks?

How do props work in React?

What is prop drilling and how can you avoid it?

Explain the Context API and its use cases.

How do you use render props?

What is the children prop?

Why is performance optimization important in React?

What is React.memo and when would you use it?

How does PureComponent differ from Component in React?

Can you explain the concept of reconciliation in React?

How can you prevent unnecessary re-renders in React?

How do you apply styles in a React application?

What is CSS-in-JS and how do you implement it in React?

Can you describe how Styled-Components work?

What are the advantages of using Sass or LESS in a React project?

How do you use inline styles in React?

What is React Router?

How do you create dynamic routes in React?

How would you pass data to routes in React Router v5+?

How do you programmatically navigate using React Router?

What are route guards and how can you implement them in React?

What are higher-order components (HOCs)?

Explain the container/presenter (smart/dumb) component pattern.

How would you implement a compound component pattern in React?

Explain the use of custom hooks in React.

What is a render prop pattern?

How do you handle forms in React?

What is controlled and uncontrolled components?

How do you validate forms in React?

What is Formik and how is it used in React forms?

How do you handle file uploads in React?

What are the benefits of using TypeScript with React?

How do you define types for props and state in TypeScript with React?

Explain how to use interfaces with React components and TypeScript.

How do TypeScript generics enhance react components?

Why is testing important in React?

What are some common testing libraries for React?

How do you test a React component with Jest?

Can you explain the difference between shallow rendering and mount rendering in Enzyme?

What is react-testing-library and how is it different from Enzyme?

What are React fragments and why are they useful?

What is React portal and when would you use it?

How does error boundary work in React?

What is server-side rendering and how is it done with React?

Can you explain the concept of suspense and lazy loading in React?

How does React affect SEO?

What strategies would you use to make a React application SEO-friendly?

How can server-side rendering improve SEO with React applications?

What is React Native and how is it different from React?

How do you bridge native modules in React Native?

Can you describe the layout system in React Native?

What is Apollo Client and how does it integrate with React?

How do you manage local state in Apollo Client?

What is Redux and how does it contrast with the Context API?

Can you detail the Redux workflow?

How do you handle side effects in Redux applications?

How do you set up a React project from scratch?

What is Babel and why do we use it with React?