Top 50 Most Frequently Asked React Interview Questions (Beginner to Advanced Guide for 2026)
Preparing for a React interview can feel overwhelming—but it doesn’t have to be.
This comprehensive guide covers the 50 most frequently asked React interview questions, carefully divided into Beginner, Intermediate, and Advanced levels. Along with clear answers, you’ll get real-world insights, practical advice, and a future-ready perspective to help you stand out in modern frontend interviews.
Beginner-Level React Interview Questions (1–17)
1. What is React?
React is an open-source JavaScript library used for building fast, interactive user interfaces, primarily for single-page applications.
2. What are the main features of React?
- Component-based architecture
- Virtual DOM
- Unidirectional data flow
- Declarative UI
- Hooks for state and lifecycle management
3. What is JSX?
JSX is a syntax extension that allows writing HTML-like code inside JavaScript, improving readability and development speed.
4. Why is React faster than traditional DOM manipulation?
React uses a Virtual DOM, which updates only the necessary parts of the UI instead of re-rendering everything.
5. What is a component in React?
Components are reusable, self-contained UI blocks that manage their own structure and behavior.
6. Functional vs Class components?
Functional components are simpler, use hooks, and are preferred in modern React, while class components rely on lifecycle methods.
7. What are props?
Props are read-only inputs passed from parent to child components.
8. What is state?
State is a mutable object that stores data affecting how a component renders and behaves.
9. What is useState?
A hook that allows functional components to manage local state.
10. What is conditional rendering?
Rendering UI elements based on conditions using logical operators or ternary expressions.
11. What is key in React lists?
Keys help React identify which items have changed, improving rendering performance.
12. What is React.Fragment?
It allows grouping elements without adding extra nodes to the DOM.
13. What are controlled components?
Form elements whose values are managed by React state.
14. What is useEffect?
A hook for handling side effects like API calls, subscriptions, or DOM updates.
15. What is lifting state up?
Sharing state between components by moving it to their closest common ancestor.
16. What is React Strict Mode?
A development tool that highlights potential problems and unsafe lifecycle usage.
17. What is the difference between React and ReactDOM?
React handles UI logic, while ReactDOM renders components to the browser DOM.
Intermediate-Level React Interview Questions (18–35)
18. What is Virtual DOM?
A lightweight copy of the real DOM that React uses for efficient UI updates.
19. What are hooks?
Hooks let you use state and lifecycle features in functional components.
20. Explain useContext.
It provides a way to pass data through the component tree without prop drilling.
21. What is prop drilling?
Passing props through multiple layers unnecessarily, which can hurt maintainability.
22. What is memoization in React?
Optimizing performance by caching results using React.memo, useMemo, or useCallback.
23. Difference between useMemo and useCallback?
useMemomemoizes valuesuseCallbackmemoizes functions
24. What are Higher-Order Components (HOC)?
Functions that take a component and return an enhanced version.
25. What is React Router?
A library for handling navigation and routing in React applications.
26. What is lazy loading?
Loading components only when needed using React.lazy and Suspense.
27. What are error boundaries?
Components that catch JavaScript errors in the component tree.
28. What is reconciliation?
React’s process of comparing old and new Virtual DOM trees.
29. What is synthetic event?
A cross-browser wrapper around native browser events.
30. How does React handle forms?
Using controlled or uncontrolled components with state or refs.
31. What is useRef used for?
Accessing DOM elements or persisting values without re-rendering.
32. What is Redux?
A predictable state management library often used with React.
33. Redux vs Context API?
Context is simpler and built-in; Redux offers better debugging and scalability.
34. What is immutability in React?
Not mutating state directly to ensure predictable updates and re-rendering.
35. What is hydration in React?
Attaching event listeners to server-rendered HTML in SSR applications.
Advanced-Level React Interview Questions (36–50)
36. What is Concurrent React?
A feature that improves responsiveness by interruptible rendering.
37. Explain Server-Side Rendering (SSR).
Rendering React components on the server for better SEO and performance.
38. What is React Fiber?
The internal engine that enables concurrent rendering.
39. How does React optimize performance?
- Memoization
- Code splitting
- Lazy loading
- Virtual DOM diffing
40. What are render props?
A pattern for sharing logic using a function as a prop.
41. What is code splitting?
Breaking bundles into smaller chunks to reduce initial load time.
42. What is Suspense used for?
Handling asynchronous rendering like lazy-loaded components.
43. Explain micro-frontends in React.
Breaking large apps into independent, deployable frontend modules.
44. How does React handle accessibility?
Using semantic HTML, ARIA attributes, and keyboard navigation support.
45. What is tree shaking?
Removing unused code during the build process.
46. What is the difference between CSR and SSR?
CSR renders on the client; SSR renders on the server for faster first paint.
47. What are Web Workers in React apps?
Used to run heavy computations without blocking the UI thread.
48. How does React work with TypeScript?
TypeScript adds type safety, improving maintainability and scalability.
49. What are design patterns commonly used in React?
- Container-Presentational
- Compound components
- Hooks-based architecture
50. What’s the future of React?
More focus on Server Components, performance optimization, and edge rendering.
