Web Development Interview Questions

1. What is a REST API?

2. Cookies vs Sessions vs JWT

3. What is CORS?

4. Difference Between GET and POST

5. REST vs GraphQL: What Is the Difference?

6. What Is OAuth?

7. What Is the Virtual DOM?

8. What Is Web Caching?

9. What Is Webpack and Bundling?

10. Server-Side vs Client-Side Rendering

11. What is a WebSocket?

12. What is the Same-Origin Policy?

13. What is CSRF?

14. What is XSS?

15. What is a Single-Page Application?

16. What is Lazy Loading?

17. What is a Service Worker?

18. What is Content Security Policy (CSP)?

19. What are HTTP Caching Headers?

20. Debouncing vs Throttling

21. What is the DOM?

22. What is Progressive Enhancement?

23. What is an HTTP Status Code?

24. What is API Versioning?

25. What Is a Closure in JavaScript?

26. What Is Hoisting in JavaScript?

27. What Is the JavaScript Event Loop?

28. Promises vs async/await: What Is the Difference?

29. What Is Prototypal Inheritance in JavaScript?

30. How Does the `this` Keyword Work in JavaScript?

31. What Is Currying in JavaScript?

32. What Is the Difference Between Event Bubbling and Capturing?

33. What Is Event Delegation and Why Use It?

34. What Is the Difference Between call, apply, and bind?

35. Shallow Copy vs Deep Copy: What Is the Difference?

36. What Is the Temporal Dead Zone in JavaScript?

37. What Is the IIFE Pattern in JavaScript?

38. What Are Generators in JavaScript and How Do They Work?

39. What Are Symbols in JavaScript and Why Use Them?

40. WeakMap vs WeakSet: What Is the Difference?

41. What Are Proxy and Reflect in JavaScript?

42. What Are Tagged Template Literals?

43. What Is Optional Chaining in JavaScript?

44. What Is Destructuring Assignment in JavaScript?

45. Spread vs Rest Operator: What Is the Difference?

46. ESM vs CommonJS: What Is the Difference?

47. What Is Tree-Shaking in JavaScript?

48. What Is Memoization in JavaScript?

49. Microtask vs Macrotask Queue: What Is the Difference?

50. What Is Strict Mode in JavaScript?

51. What Is Type Coercion in JavaScript?

52. What Is NaN and How Do You Check for It?

53. What Is the CSS Box Model?

54. CSS Flexbox vs Grid: What Is the Difference?

55. How Does CSS Specificity Work?

56. What Are the CSS Position Values and How Do They Differ?

57. How Do z-index and Stacking Contexts Work?

58. What Are CSS Custom Properties (CSS Variables)?

59. What Are CSS Media Queries and How Do They Work?

60. What Are the Core Principles of Responsive Web Design?

61. What Are CSS Pseudo-Elements and How Do They Differ From Pseudo-Classes?

62. What Is the Difference Between CSS Transitions and CSS Animations?

63. How Does CSS Transform Enable GPU-Accelerated Animation?

64. What Is BEM Methodology and Why Use It in CSS?

65. What Is the CSS-in-JS Approach and When Should You Use It?

66. What Is Critical CSS Extraction and Why Does It Matter?

67. What Is the Difference Between Reflow and Repaint?

68. How Does React Reconciliation Work?

69. Why Does React Need Keys for List Items?

70. What Are the Rules of Hooks and Why Do They Exist?

71. useEffect vs useLayoutEffect: What Is the Difference?

72. useMemo vs useCallback: What Is the Difference?

73. Context API vs Redux: When Should You Use Each?

74. Controlled vs Uncontrolled Components: What Is the Difference?

75. What Is Prop Drilling and How Do You Avoid It?

76. What Is React Fiber Architecture?

77. What Is Hydration in React?

78. What Is React Suspense and How Does It Work?

79. What Are Error Boundaries in React?

80. What Are React Portals and When Do You Use Them?

81. What Are the Main State Management Patterns in Frontend Apps?

82. SSR vs SSG vs ISR: What Is the Difference?

83. What Is the Critical Rendering Path?

84. What Are Core Web Vitals — LCP, FID/INP, and CLS?

85. What Are Code-Splitting Strategies and Why Do They Matter?

86. Preload vs Prefetch: What Is the Difference?

87. What Are Key Image Optimization Techniques for the Web?

88. Gzip vs Brotli: How Do These Compression Algorithms Compare?

89. What Was HTTP/2 Server Push, and Why Was It Deprecated?

90. What Are Resource Hints (preload, prefetch, preconnect)?

91. What Is the Difference Between defer and async Scripts?

92. What Is List Virtualization and Why Use It?

93. What Is Clickjacking and How Do You Prevent It?

94. What Is SQL Injection and How Do You Prevent It?

95. What Are the Secure and HttpOnly Cookie Attributes?

96. What Is the SameSite Cookie Attribute and How Does It Prevent CSRF?

97. What Is Subresource Integrity (SRI)?

98. What Are JWT Security Best Practices?

99. What Is a Session Fixation Attack and How Do You Prevent It?

100. What Is HTTPS and What Causes Mixed Content Errors?

101. How Do You Design a Good GraphQL Schema?

102. WebSockets vs Server-Sent Events: When to Use Each?

103. What Are Webhooks and How Do They Work?

104. What Are Common API Rate Limiting Strategies?

105. What Is Idempotency in REST APIs?

106. HTTP Methods: Safe vs. Idempotent, What Is the Difference?

107. What Do the HTTP Status Code Families Mean?

108. What Are the Main API Pagination Strategies?

109. What Are the Main API Authentication Methods?

110. What Is Refresh Token Rotation?

111. What Are CORS Preflight Requests?

112. What Does Babel Do When Transpiling JavaScript?

113. ES Modules vs. Bundlers: How Do They Relate?

114. What Are Source Maps and Why Do They Matter?

115. What Is ESLint and Why Does Linting Matter?

116. DOM vs Shadow DOM: What Is the Difference?

117. What Are Web Components?

118. What Are Service Worker Caching Strategies?

119. What Is a Progressive Web App (PWA)?

120. IndexedDB vs localStorage vs Cookies: When Do You Use Each?

121. What Are the Size Limits of Web Storage Mechanisms?

122. What Are ARIA Attributes and When Should You Use Them?

123. Why Does Semantic HTML Matter?

124. How Do You Build Keyboard-Accessible Web Interfaces?

125. Repaint vs Reflow: How Do They Affect Rendering Performance?

126. What Is requestAnimationFrame and When Should You Use It?

127. What Is the Intersection Observer API and Why Use It?

128. What Is the Mutation Observer API and When Should You Use It?

129. What Is the Resize Observer API and Why Is It Useful?

130. map, filter, and reduce: How Do They Differ?

131. What Does Array Sort Stability Mean?

132. How Does the Event Loop Order Microtasks and Macrotasks?

133. Promise.all vs Promise.allSettled: When to Use Each?

134. Promise.race vs Promise.any: What Sets Them Apart?

135. What Are Async Generators in JavaScript?

136. How Do Modern Module Bundlers Like Vite, esbuild, and Webpack Compare?

137. How Does CSS Grid grid-template-areas Work?

138. What Do justify-content, align-items, and align-self Do in Flexbox?

139. What Are CSS Container Queries and How Do They Differ from Media Queries?

140. What Are CSS Cascade Layers (@layer) and Why Do They Matter?

141. How Does Native CSS Nesting Syntax Work?

142. What Are CSS Viewport Units (vh, vw, dvh, svh, lvh)?

143. How Do You Implement Dark Mode in a Web App?

144. How Do CSS Custom Media Queries (@custom-media) Work?

145. What Are React Server Components?

146. What Are the Basics of the Next.js App Router?

147. What Is React Concurrent Rendering?

148. How Does React Strict Mode Change Component Behavior?

149. What Is forwardRef in React and When Do You Need It?

150. How Do React.lazy and Suspense Enable Code Splitting?

151. How Do You Design a Good Custom React Hook?

152. What Are Higher-Order Components (HOCs) in React?

153. What Is the Render Props Pattern in React?

154. What Is the Compound Components Pattern in React?

155. What Are State Machines and Why Use Them in Frontend Code?

156. What Are Optimistic UI Updates and How Do You Implement Them?

157. How Do You Implement a Debounced Search Input?

158. How Do You Implement Infinite Scroll?

159. What Are Skeleton Loading Screens and Why Use Them?

160. How Do You Test a Web App for Accessibility?

161. How Do You Manage Focus in a Single-Page Application?

162. What Are ARIA Live Regions and When Do You Use Them?

163. What Color Contrast Ratios Does WCAG Require and Why?

164. How Do You Make Custom Components Screen-Reader Compatible?

165. What Is the Browser Rendering Pipeline?

166. What Is Layout Thrashing and How Do You Avoid It?

167. What Are Passive Event Listeners and Why Do They Matter?

168. When Should You Use requestIdleCallback?

169. What Are Web Workers and When Should You Use Them?

170. Shared Workers vs Web Workers: What Is the Difference?

171. What Is Offline-First Architecture?

172. What Is the Background Sync API?

173. How Do Web Push Notifications Work?

174. What Is the Cache API and How Does It Differ From HTTP Caching?

175. HTTP/1.1 vs HTTP/2: What Changed?

176. What Is HTTP/3 and How Does QUIC Change Things?

177. What Is DNS Prefetching and When Should You Use It?

178. What Happens During a TLS Handshake?

179. What CDN Caching Strategies Should You Know?

180. Monorepo vs Polyrepo for Frontend Projects: How Do You Choose?

181. What Is Micro-Frontend Architecture?

182. What Is Webpack Module Federation and How Does It Work?

183. How Do Feature Flags Work in Frontend Development?

184. How Does A/B Testing Work on the Frontend?

185. What Are Form Validation Strategies on the Web?

186. Controlled Forms in React: Performance Tradeoffs?

187. How Do You Handle File Uploads on the Web?

188. How Does the HTML5 Drag and Drop API Work?

189. How Does the Web Clipboard API Work?

190. How Does the Geolocation API Work in the Browser?

191. What Is the Web Animations API and How Does It Compare to CSS Animations?

192. Canvas vs SVG: When Should You Use Each for Web Graphics?

193. What Is WebGL and How Does It Render Graphics in the Browser?

194. What Is the Web Audio API and How Does the Audio Graph Work?

195. How Does Browser Storage Quota Management Work?

196. How Do You Manage Third-Party Script Performance?

197. How Do Lighthouse Audits Work and What Do They Measure?

198. How Do You Use Bundle Analysis Tools to Optimize JavaScript?

199. What Is Dead Code Elimination and How Does It Work?

200. What Is CSS Specificity and How Do You Resolve Conflicts?

201. What Is the Atomic CSS Approach?

202. What Is Utility-First CSS and How Does It Differ From Semantic CSS?

203. What Are CSS Modules and How Do They Solve Global Scope Problems?

204. What Are the Tradeoffs of Using Styled-Components (CSS-in-JS)?

205. TypeScript vs JavaScript: What Is the Difference?

206. What Is Type Narrowing in TypeScript?

207. What Are Generics in TypeScript and Why Use Them?

208. What Are TypeScript Utility Types Like Partial and Pick?

209. What Are Discriminated Unions in TypeScript?

210. Monolithic vs Microservice: How Does the Frontend Integrate?

211. What Is the Backend-for-Frontend (BFF) Pattern?

212. What Is the API Gateway Pattern?

213. How Does Caching Differ Between GraphQL and REST?

214. What Is the GraphQL N+1 Problem and How Do You Solve It?

215. What Are HTTP Security Headers and Why Do They Matter?

216. How Do CSP Nonces Prevent Inline Script Injection?

217. What Does the Referrer-Policy Header Control?

218. What Is the Permissions-Policy Header Used For?

219. What Is the Trusted Types API and How Does It Prevent DOM XSS?

220. What Is a Web Performance Budget?

221. What Is the Time to Interactive (TTI) Metric?

222. What Is First Contentful Paint (FCP)?

223. What Is Total Blocking Time (TBT)?

224. What Is the Speed Index Metric?