Introduction

Interviewing for a Next.js role? Whether you're aiming to work on performance-optimized web applications or server-rendered React apps, Next.js interviews can be tough if you're unprepared. Knowing the most common Next.js interview questions can drastically improve your confidence and help you perform at your best. This guide will cover the 30 most frequently asked Next.js interview questions, why they’re asked, and how to answer them like a pro.

What are Next.js interview questions?

Next.js interview questions are queries that test your understanding of the Next.js framework—a popular React-based framework used for server-side rendering (SSR), static site generation (SSG), routing, and performance optimization. These questions can span basic concepts to advanced topics like middleware, streaming, and server components.

Why do interviewers ask Next.js questions?

Interviewers ask Next.js questions to assess your:

• Understanding of modern web development best practices

• Experience building performant applications with React and Next.js

• Familiarity with SSR, SSG, ISR, and other core Next.js capabilities

• Problem-solving and architectural thinking for real-world scenarios

Preview: Top 30 Next.js Interview Questions

1. What is Next.js and what are its main features?

2. How do you create a new Next.js application?

3. Explain the difference between server-side rendering (SSR) and static site generation (SSG) in Next.js.

4. How does routing work in Next.js?

5. What is dynamic routing in Next.js and how is it implemented?

6. Explain the purpose of the pages directory in a Next.js project.

7. What is the difference between getServerSideProps and getStaticProps?

8. How do you implement API routes in Next.js?

9. What is the purpose of the _app.js file in Next.js?

10. How do you optimize images in Next.js?

11. Explain the concept of code splitting in Next.js.

12. What is the purpose of the next.config.js file?

13. How do you implement authentication in a Next.js application?

14. What is Incremental Static Regeneration (ISR) in Next.js?

15. How do you handle environment variables in Next.js?

16. Explain the difference between Link component and <a> tag in Next.js.

17. What is the purpose of getStaticPaths in Next.js?

18. How do you implement internationalization (i18n) in Next.js?

19. What are the main scripts in a Next.js package.json file and their purposes?

20. How do you implement custom error pages in Next.js?

21. Explain the concept of middleware in Next.js.

22. How do you implement SEO optimization in a Next.js application?

23. What is the difference between pages directory and app directory in Next.js 13+?

24. How do you implement server-side streaming in Next.js?

25. Explain the concept of React Server Components in Next.js.

26. How do you implement data fetching on the client side in Next.js?

27. What is the purpose of the Head component in Next.js?

28. How do you implement lazy loading of components in Next.js?

29. Explain how you would optimize the performance of a large-scale Next.js application.

30. How do you deploy a Next.js application?

    
    

1. What is Next.js and what are its main features?

Why you might get asked this:
Interviewers often ask "What is Next.js and what are its main features?" to assess your foundational understanding of the framework and its advantages over using plain React.

How to answer:
Define Next.js as a React framework that supports server-side rendering, static site generation, and other modern web capabilities. Highlight key features like file-based routing, API routes, image optimization, and fast performance through pre-rendering.

Example answer:
"Next.js is a React-based framework that enables server-side rendering and static site generation. It offers features like file-based routing, built-in API routes, image optimization, and improved performance out of the box. These capabilities make it ideal for building fast, SEO-friendly web applications."

2. How do you create a new Next.js application?

Why you might get asked this:
This question checks if you’re familiar with the basic setup and tooling around Next.js projects, which is essential for hands-on development.

How to answer:
Explain that you can create a new app using create-next-app CLI. Mention using npx, npm, or yarn depending on the setup.

Example answer:
"You can create a new Next.js application using the command npx create-next-app@latest. This sets up a new project with all the default configurations, including the pages directory and a development server. You can also use npm init next-app or yarn create next-app depending on your package manager."

3. Explain the difference between server-side rendering (SSR) and static site generation (SSG) in Next.js.

Why you might get asked this:
Interviewers want to test your understanding of rendering methods and when to use each to optimize performance and user experience.

How to answer:
Define SSR as generating the page at request time using getServerSideProps. Explain SSG as generating HTML at build time using getStaticProps.

Example answer:
"Server-side rendering (SSR) means the HTML is generated on each request using getServerSideProps, ensuring up-to-date content. Static site generation (SSG) uses getStaticProps to build the HTML at compile time, leading to faster performance and better scalability. SSG is ideal for pages that don’t change frequently."

4. How does routing work in Next.js?

Why you might get asked this:
This evaluates your knowledge of file-based routing and how it simplifies navigation compared to traditional React routing setups.

How to answer:
Explain that routing in Next.js is file-based, meaning each file inside the pages directory becomes a route. Dynamic and nested routes follow the file structure.

Example answer:
"In Next.js, routing is based on the file structure inside the pages directory. For example, pages/about.js becomes /about. Nested folders represent nested routes, and dynamic routes are created using square brackets like [id].js for paths like /post/123."

5. What is dynamic routing in Next.js and how is it implemented?

Why you might get asked this:
Dynamic routing is a key feature in building scalable apps. This checks if you know how to handle variable routes like blog slugs or product IDs.

How to answer:
Mention that dynamic routing uses square brackets (e.g., [slug].js). You should explain how to use getStaticPaths and getStaticProps to generate content.

Example answer:
"Dynamic routing in Next.js allows you to create pages with dynamic segments by naming the file [param].js. For example, [id].js handles routes like /product/123. To pre-render dynamic pages, you use getStaticPaths to define available paths and getStaticProps to fetch data for each."

6. Explain the purpose of the pages directory in a Next.js project.

Why you might get asked this:
This question is common to ensure you understand how Next.js handles routing and separates concerns in the project structure.

How to answer:
Clarify that every file in the pages directory automatically maps to a route, including API routes in the pages/api folder.

Example answer:
"The pages directory defines the routes of your application. Each .js or .tsx file corresponds to a route based on its file path. Additionally, the pages/api folder is used to define backend API routes that run server-side in a serverless fashion."

7. What is the difference between getServerSideProps and getStaticProps?

Why you might get asked this:
This tests your knowledge of data fetching strategies and how to choose between them for performance or content freshness.

How to answer:
Compare getServerSideProps (runs at request time) with getStaticProps (runs at build time). Mention use cases for both.

Example answer:
"getServerSideProps runs on each request and is used when data needs to be fresh or dynamic. getStaticProps runs at build time, generating static HTML for better performance. Use getStaticProps for content that doesn't change often, and getServerSideProps for dynamic, user-specific content."

8. How do you implement API routes in Next.js?

Why you might get asked this:
Interviewers want to see if you know how to build full-stack features without needing a separate backend.

How to answer:
Explain that you can add serverless functions in the pages/api directory. Each file becomes an API endpoint.

Example answer:
"To create an API route in Next.js, you create a file in the pages/api directory. For example, pages/api/hello.js defines a route at /api/hello. Each file exports a function that handles the request and response, acting as a serverless function."

9. What is the purpose of the _app.js file in Next.js?

Why you might get asked this:
This tests your understanding of customizing the app's behavior, including layout and global configurations.

How to answer:
Explain that _app.js allows you to override the default App component to persist layout and wrap pages with providers or global styles.

Example answer:
"The _app.js file is used to initialize pages. It allows you to persist layout between pages, inject global CSS, and wrap the app with context providers. By customizing _app.js, you can apply settings or logic that should apply across all pages."

10. How do you optimize images in Next.js?

Why you might get asked this:
This shows whether you're aware of performance enhancements in Next.js and how to use built-in tools.

How to answer:
Mention the next/image component and its benefits like automatic resizing, lazy loading, and format optimization.

Example answer:
"Next.js provides an Image component from next/image that optimizes images automatically. It supports lazy loading, responsive images, and automatic format conversion like WebP. This helps reduce load times and improves performance metrics like Core Web Vitals."

11. Explain the concept of code splitting in Next.js.

Why you might get asked this:
Interviewers ask this to evaluate your understanding of performance optimization and how Next.js handles efficient bundling.

How to answer:
Explain that code splitting is automatic in Next.js, with each page and dynamic import creating separate bundles that load only when needed.

Example answer:
"Next.js performs automatic code splitting by creating separate JavaScript bundles for each page. When a user navigates to a page, only the necessary code for that page is loaded. You can also use dynamic imports with next/dynamic to load components on demand, reducing initial load time and improving performance."

12. What is the purpose of the next.config.js file?

Why you might get asked this:
This question tests your knowledge of project configuration and customization options in a Next.js app.

How to answer:
State that next.config.js is used to modify the default behavior of Next.js, including custom headers, redirects, rewrites, image domains, and more.

Example answer:
"The next.config.js file allows you to customize and extend Next.js configurations. You can define custom headers, environment variables, image domains, rewrites, redirects, and more. It helps tailor the app’s behavior to specific deployment or development needs."

13. How do you implement authentication in a Next.js application?

Why you might get asked this:
Authentication is crucial for protected routes and user sessions, so interviewers ask to see if you can implement secure login systems.

How to answer:
Describe using libraries like NextAuth.js or JWT. Explain protecting pages using getServerSideProps or middleware for server-side auth.

Example answer:
"You can implement authentication in Next.js using libraries like NextAuth.js, which integrates easily with providers like Google, GitHub, or email. For custom setups, you can use JWTs and check authentication in getServerSideProps or middleware. Protected routes can be restricted by validating tokens on the server before rendering."

14. What is Incremental Static Regeneration (ISR) in Next.js?

Why you might get asked this:
ISR is one of Next.js's standout features. This checks your grasp of modern hybrid rendering techniques.

How to answer:
Explain that ISR allows you to update static content after build time, combining the benefits of SSG and dynamic updates.

Example answer:
"Incremental Static Regeneration (ISR) lets you update static pages after the site has been built. By setting a revalidate time in getStaticProps, Next.js will regenerate the page in the background at specified intervals, giving users up-to-date content without rebuilding the whole site."

15. How do you handle environment variables in Next.js?

Why you might get asked this:
Environment config is essential for deploying apps securely. This checks if you can manage secrets and runtime config.

How to answer:
Mention using .env.local and prefixing public variables with NEXT_PUBLIC_. Explain differences between server and client access.

Example answer:
"Next.js supports environment variables via .env.local, .env.development, and .env.production files. Server-only variables stay private. To expose a variable to the browser, prefix it with NEXT_PUBLIC_. You can access them using process.env.VARIABLE_NAME."

16. Explain the difference between Link component and <a> tag in Next.js.

Why you might get asked this:
This question tests your understanding of client-side navigation and how Next.js improves performance with routing.

How to answer:
Explain that the Link component enables client-side transitions for faster navigation, while <a> reloads the page.

Example answer:
"Next.js’s Link component enables client-side routing, allowing for faster transitions without a full page reload. You wrap an <a> tag inside a Link or use the Link's legacyBehavior to render an anchor tag. Using plain <a> tags without Link causes a full page refresh, breaking SPA behavior."

17. What is the purpose of getStaticPaths in Next.js?

Why you might get asked this:
This is a core function when working with dynamic routes in static generation. It checks your knowledge of SSG.

How to answer:
Define getStaticPaths as a function used with dynamic routes to generate paths at build time. It works with getStaticProps.

Example answer:
"getStaticPaths is used in combination with getStaticProps for dynamic routes that need to be statically generated. It returns an array of paths that Next.js should pre-render at build time, enabling fast page loads for dynamic content like blog posts or product pages."

18. How do you implement internationalization (i18n) in Next.js?

Why you might get asked this:
Global apps require localization. This checks if you're comfortable enabling language-specific routes and content.

How to answer:
Mention the built-in i18n config in next.config.js and how to use locale-specific routes and content.

Example answer:
"Next.js has built-in support for internationalization. You can define locales in next.config.js using the i18n field. Next.js will handle locale-specific routing (e.g., /en, /fr) and allow you to detect and switch languages. For content, you can use libraries like next-intl or react-i18next."

19. What are the main scripts in a Next.js package.json file and their purposes?

Why you might get asked this:
This checks your understanding of basic project workflow and how to manage different app environments.

How to answer:
List common scripts: dev, build, start, lint, and explain their purposes.

Example answer:
"The main scripts in a Next.js package.json include:\n- dev: starts the development server with hot reloading\n- build: compiles the app for production\n- start: starts the production server after build\n- lint: runs ESLint to check for code issues\nThese scripts help manage the full app lifecycle from development to deployment."

20. How do you implement custom error pages in Next.js?

Why you might get asked this:
It evaluates whether you can handle user-friendly error states, an important part of UX.

How to answer:
Explain creating special files like 404.js or _error.js in the pages directory to handle different error states.

Example answer:
"To create a custom 404 page, add a 404.js file in the pages directory. For other errors, you can use _error.js to customize the appearance of general error messages. These pages improve user experience by making errors feel polished and helpful."

Let’s wrap it up with the final questions 21 to 30, keeping the same structure and SEO-optimized formatting.

21. Explain the concept of middleware in Next.js.

Why you might get asked this:
Interviewers want to assess if you can apply logic before a request is completed—critical for tasks like auth, redirects, and A/B testing.

How to answer:
Define middleware as code that runs before a request is completed. Explain it executes in the Edge Runtime and can modify the response or redirect.

Example answer:
"Middleware in Next.js allows you to run code before a request is completed. It runs on the Edge Runtime and can be used for tasks like authentication, redirects, and feature flags. Middleware is defined in a middleware.js file at the root or in any directory and uses a NextResponse to modify requests or responses."

22. How do you implement SEO optimization in a Next.js application?

Why you might get asked this:
SEO is a major benefit of using Next.js. This checks if you know how to structure content for discoverability.

How to answer:
Mention server-rendering benefits, the Head component, and best practices like setting meta tags, Open Graph tags, and canonical URLs.

Example answer:
"Next.js improves SEO through server-side rendering and static generation. You can use the Head component from next/head to set meta tags, titles, descriptions, and Open Graph tags for social sharing. It’s also important to use semantic HTML, structured data, and clean URLs for better indexing."

23. What is the difference between pages directory and app directory in Next.js 13+?

Why you might get asked this:
This is a newer topic testing your familiarity with the App Router and the direction Next.js is heading.

How to answer:
Compare the legacy pages directory with the new app directory introduced in Next.js 13. Explain layout and server component support.

Example answer:
"The pages directory uses the traditional file-based routing with limited layouts and client-focused components. The app directory, introduced in Next.js 13, supports the App Router, layouts, nested routing, and React Server Components. It enables more flexible and scalable app architecture with improved data loading and streaming."

24. How do you implement server-side streaming in Next.js?

Why you might get asked this:
Streaming helps with performance and perceived loading speed. This checks if you're aware of advanced SSR patterns.

How to answer:
Mention using the App Router and React Server Components. Explain that parts of the UI can be streamed as they're ready.

Example answer:
"In the App Router (Next.js 13+), server-side streaming allows parts of the page to be rendered and sent to the client incrementally. This improves time-to-first-byte and user experience. You can use async components and Suspense to control what loads when, streaming the UI in chunks as data becomes available."

25. Explain the concept of React Server Components in Next.js.

Why you might get asked this:
Server Components are a core innovation in React and Next.js. Interviewers want to see if you're up-to-date with new features.

How to answer:
Define Server Components as components rendered on the server that never send JavaScript to the client. Mention benefits like reduced bundle size.

Example answer:
"React Server Components (RSC) are components rendered on the server and never included in the client-side bundle. This allows you to fetch data directly inside components without sending extra JS to the browser. In Next.js, you can use Server Components by default in the App Router, improving performance and load time."

26. How do you implement data fetching on the client side in Next.js?

Why you might get asked this:
Client-side fetching is still common for dynamic UIs. This tests your ability to balance SSR and client interactivity.

How to answer:
Explain using useEffect, SWR, or React Query. Clarify when to use client-side fetching over server-side methods.

Example answer:
"You can implement client-side data fetching in Next.js using useEffect and fetch, or libraries like SWR and React Query for caching and revalidation. Client-side fetching is useful for user-specific or frequently updated data that doesn’t need to be SEO-optimized."

27. What is the purpose of the Head component in Next.js?

Why you might get asked this:
This evaluates your knowledge of document metadata and improving accessibility and SEO.

How to answer:
Explain that the Head component from next/head allows you to set metadata like <title>, <meta>, and more for each page.

Example answer:
"The Head component in Next.js, imported from next/head, lets you add elements to the HTML document head. You can set dynamic page titles, meta descriptions, keywords, Open Graph tags, and other metadata to improve SEO and control how pages appear in search and social previews."

28. How do you implement lazy loading of components in Next.js?

Why you might get asked this:
This tests your performance optimization skills and ability to reduce initial bundle size.

How to answer:
Mention next/dynamic for dynamic imports. Optionally reference native React.lazy.

Example answer:
"Next.js supports lazy loading through the next/dynamic function. You can dynamically import components so they load only when needed. This reduces the initial bundle size and improves page load performance. You can also specify loading placeholders and disable SSR if needed."

29. Explain how you would optimize the performance of a large-scale Next.js application.

Why you might get asked this:
Interviewers want to know if you can handle real-world scaling challenges and deliver fast, efficient web apps.

How to answer:
List strategies like image optimization, code splitting, lazy loading, ISR, caching, CDN usage, and using React.memo or Server Components.

Example answer:
"To optimize a large-scale Next.js app, I would use features like Incremental Static Regeneration (ISR), lazy loading components with next/dynamic, code splitting, and the Image component for responsive image delivery. I'd implement caching at the edge, enable gzip compression, reduce JavaScript bundle size, and monitor Core Web Vitals using tools like Lighthouse or Vercel Analytics."

30. How do you deploy a Next.js application?

Why you might get asked this:
Deployment readiness is crucial. This question ensures you understand how to take a project live.

How to answer:
Explain common deployment platforms (e.g., Vercel, Netlify) and how to build and start the app in production.

Example answer:
"You can deploy a Next.js app easily on Vercel, which is built by the creators of Next.js. Just connect your Git repo and Vercel handles the rest, including build and deploy steps. For manual deployment, run npm run build and npm run start on a Node.js server or containerized environment. Next.js also supports static exports using next export."

Here’s a polished Conclusion and FAQ section to wrap up your SEO-optimized blog post on 30 Most Common Next.js Interview Questions You Should Prepare For.

Conclusion

Crushing a Next.js interview comes down to preparation and confidence. By understanding these 30 common questions—and how to answer them—you’re already ahead of the game. Whether you’re brushing up on SSR vs. SSG or diving into React Server Components, mastering these concepts will help you stand out.