Next.js Interview Questions and Answers (original) (raw)

Last Updated : 24 Sep, 2025

Next.js is a React-based framework for building fast, scalable, and SEO-friendly web applications. It provides modern features for both frontend and backend development, making it suitable for small projects to enterprise-grade applications.

Next.js Basic Interview Questions

1. How Next.js Works?

Next.js works as a React framework that handles rendering, routing, and optimization automatically, making web apps faster and SEO-friendly.

This enables developers to build full-stack, production-ready applications with minimal configuration.

next_js_interview_questions_and_answers_2025

2. What are API Routes?

Next.js lets you create backend endpoints inside your project without setting up a separate server (like Express or Django).

3. What do you mean by SSR?

SSR stands for **Server-Side Rendering, a technique where the server generates the full HTML of a page before sending it to the client. Key points:

4. How does Next.js handle client-side navigation?

Next.js uses a client-side navigation approach that leverages the HTML5 History API. This enables smooth transitions between pages on the client side without a full page reload. The framework provides a built-in Link component that facilitates client-side navigation, and it supports both traditional anchor (<a>) tags and programmatically navigating through the next/router module.

Here's an overview of how Next.js handles client-side navigation:

**Link Component:

import Link from 'next/link';

const MyComponent = () => ( Go to another page );

`

**Programmatic Navigation:

import { useRouter } from 'next/router';

const MyComponent = () => { const router = useRouter(); const handleClick = () => { router.push('/another-page'); };

return (
    <button onClick={handleClick}>
        Go to another page
    </button>
);

};

`

5. Explain the concept of dynamic routing in Next.js:

Dynamic routing in Next.js allows developers to create routes with dynamic parameters, enabling pages to handle different data or content based on these parameters. Key points:

6. What is meant by Styled JSX in Next.js?

Styled JSX is a CSS-in-JS library used in Next.js to create encapsulated and scoped styles for components. Key points:

7. Difference between the pre-rendering types available in Next.js.

**Static Generation (SG) **Server-Side Rendering (SSR)
HTML is pre-generated at build time. HTML is generated on each request.
The pre-generated HTML can be reused on every request. HTML is generated anew for each request.
Recommended for performance and efficiency. Suitable for cases where content changes frequently or cannot be determined at build time.
Export the page component or use '**getStaticProps' Export '**getServerSideProps'
Less dependent on server resources during runtime. Depends on server resources for generating content dynamically.
Typically faster as HTML is pre-generated. Can introduce higher server load due to on-the-fly HTML generation.
Easily cache static HTML. Requires server-side caching mechanisms.
Scales well as static content can be served efficiently. May require additional server resources to handle dynamic content generation.

8. What is client-side rendering, and how does it differ from server-side rendering?

**Client-side rendering (CSR) renders web pages in the browser using JavaScript after the initial HTML, CSS, and JavaScript are delivered from the server.Key points:

9. How do you pass data between pages in a Next.js application?

There are multiple ways to pass data between pages:

10. What is the difference between Next.js and React JS?

**Next.js **React
The Next.js framework was developed by Vercel. The React front-end library was originated by Facebook.
Next.js, an open-source framework based on Node.js and Babel, seamlessly integrates with React to facilitate the development of single-page apps. React, a JavaScript library, empowers the construction of user interfaces through the assembly of components.
Supports SSR and Static Site Generation (SSG) Primarily client-side rendering (CSR)
Built-in features like Image Optimization, SSR, and automatic static optimization No out-of-the-box performance optimizations
Enhanced by SSR and SSG for better SEO and faster load times Requires extra configuration for SEO optimization

11. What is the purpose of the public folder in Next.js? How do you serve static files like images, fonts, and icons?

The public folder stores static assets that are served directly to the browser without processing. It’s ideal for images, fonts, icons, and other static files.

Example:

JavaScript `

// File: public/logo.png // Usage in pages/index.js export default function HomePage() { return (

Logo
); }

`

In this Example:

12. How do you add meta tags and titles to pages in Next.js using the Head component? Why is this important for SEO?

The Head component from next/head is used to add meta tags, titles, and other head elements to a page. This allows each page to have custom SEO attributes.

Example:

JavaScript `

import Head from "next/head";

export default function HomePage() { return ( <> My Next.js App

Welcome to My Next.js App

</> ); }

`

**Importance for SEO:

13. What is Hot Module Replacement (HMR) in Next.js, and how does it improve the development experience?

Hot Module Replacement (HMR) is a feature in Next.js that updates modules in a running application without requiring a full page reload. Key Points:

14. What is the difference between layouts and templates in Next.js App Router?

App Router, layouts and templates are used to structure pages, but they serve different purposes:

**Layouts:

**Templates:

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

Next.js applications can be deployed on multiple platforms depending on the rendering strategy and hosting preferences.

16. What is the difference between getServerSideProps & getStaticProps functions in Next.js?

**getServerSideProps **getStaticProps
Executes on every request. Executes at build time.
Used for server-side rendering (SSR). Used for static site generation (SSG).
Suitable for pages with frequently changing or dynamic content. Ideal for pages with relatively static content that can be determined at build time.
Fetches data on every request, allowing for real-time updates. Fetches data at build time, so the data is static until the next build.
Receives a context object containing information about the request. Also receives a context object, but primarily used for dynamic parameters.
Handles errors during each request. Errors during data fetching result in a build-time error.
Returns an object with a props key. Returns an object with a props key, but may also include a revalidate key for incremental static regeneration.
Tends to be slower due to on-the-fly data fetching on each request. Generally faster as data is fetched at build time, reducing server load.

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

The 'getStaticPaths' function is used to generate dynamic routes for pages with dynamic data. Key points:

18. What is the purpose of the useEffect hook in React, and how does it relate to Next.js?

In Next.js, the useEffect hook is used to perform side effects in functional components, such as fetching data, updating the DOM, or subscribing to events. Key points in Next.js:

19. What do you understand by code splitting in Next.js?

Code splitting stands out as one of the most compelling features provided by webpack. This functionality allows us to divide our code into multiple bundles, which can be loaded either on-demand or in parallel. Its primary purpose is to create smaller bundles and enables us to manage the prioritization of resource loading, ultimately contributing significantly to improved load times.

There are mainly three approaches to code splitting:

Its primary purpose is to facilitate the creation of pages that never load unnecessary code.

20. How do you handle data fetching in Next.js?

Data retrieval from an external API or database can be achieved using the built-in functions, namely, `getStaticProps` or `getServerSideProps`. The `getStaticProps` function fetches data during the build process and provides it as props to the page, whereas `getServerSideProps` fetches data for each incoming request. Alternatively, client-side data fetching libraries such as `axios` or `fetch` can also be employed in conjunction with the `useEffect` or `useState` hooks.

21. What are the different options for styling Next.js apps?

Next.js provides multiple ways to style applications, each with its own use case:

When choosing a styling approach, consider performance, maintainability, and developer familiarity with the method.

22. How do you work with custom server middleware in Next.js?

Custom server middleware is added by creating a Node.js server. Key points:

23. Explain the purpose of the _app.js file in Next JS.

The _app.js file is the main component for a Next.js application and allows overriding the default App component. Key points:

24. How would you implement server-side rendering (SSR) for a Next JS page?

JavaScript `

import React from 'react';

const PageAbout = ({ dataFromServer }) => { return

{dataFromServer}
; };

export async function getServerSideProps() { const dataFromServer = 'Server-rendered data for this page';

return {
    props: {
        dataFromServer,
    },
};

}

export default PageAbout;

`

25. Explain the concept of "Serverless" deployment in the context of Next JS. How does it work, and what are the advantages?

Serverless deployment means hosting your Next.js app without managing dedicated servers. Instead, your code runs in lightweight, on-demand functions (lambdas) provided by platforms like Vercel, Netlify, or AWS Lambda. Each API route or server-side rendering (SSR) request is handled by an isolated function that scales automatically.

**How It Works

**Advantages

26. What are some best practices for debugging and testing Next JS applications?

Debugging and testing are crucial to ensure a Next.js application works correctly and efficiently. Following best practices helps catch issues early and maintain reliable code.

27. Why use Create Next App?

create-next-app allows you to swiftly initiate a new Next.js application. Officially maintained by the creators of Next.js, it offers several advantages:

28. What is Image Component and Image Optimization in Next.js?

The Next.js Image component, next/image, represents a modern evolution of the HTML <img> element with built-in performance enhancements tailored for the contemporary web.

29. What is Environment Variables in Next.js?

Next.js is equipped with native support for managing environment variables, providing the following capabilities:

30. What is Docker Image in Next.js?

Next.js is deployable on hosting providers that offer support for Docker containers. This approach is applicable when deploying to container orchestrators like Kubernetes or HashiCorp Nomad, or when operating within a single node on any cloud provider.

To implement this deployment method:

Next.js Intermediate Interview Questions

31. How can you fetch data in Next.js and when to use each method?

Next.js provides multiple ways to fetch data, depending on whether you need it at build time, request time, or on the client side. Choosing the right method improves performance, user experience, and SEO.

33. Explain the concept of "prefetching" in Next.js and how it impacts performance.

Prefetching in Next.js automatically downloads JavaScript and assets for linked pages in the background.

33. Can you explain how to internationalize a Next.js application to support multiple languages?

Next.js supports internationalization (i18n) using libraries like next-i18next or custom solutions.

34. How can you handle cross-origin requests (CORS) in a Next.js application when making API requests to a different domain?

CORS is controlled by the server or API endpoint receiving the request.

35. What is serverless architecture, and how does it relate to Next.js?

Serverless architecture is a cloud computing model where the provider manages infrastructure and automatically scales resources based on demand.

36. How do you optimize the performance of a Next.js application?

Optimizing the performance of a Next.js application involves various strategies such as:

37. Explain the purpose of the getServerSideProps function.

The getServerSideProps function in Next.js plays a crucial role in enabling server-side rendering (SSR) for dynamic pages. It allows pages to fetch data on the server during each request, ensuring that content is always fresh and up-to-date. Key points:

38. What is the purpose of the next.config.js excludes property?

The excludes property in the next.config.js file is used to specify patterns for files and directories that should be excluded from the automatic code splitting and bundling performed by Next.js. By defining exclusion patterns, developers can control which files are not subject to the default behavior of code splitting.

Here's an example of how the excludes property can be used in next.config.js:

JavaScript `

// next.config.js module.exports = { excludes: ['/path/to/excluded/file.js', //node_modules//], // other configurations... }

`

The headers property in the next.config.js file is used to define custom HTTP headers that should be included in the responses served by your Next.js application. This property allows developers to set various HTTP headers, such as caching policies, security-related headers, and other custom headers, to control how browsers and clients interact with the application.

Here's an example of how the headers property can be used:

JavaScript `

// next.config.js module.exports = { async headers() { return [ { source: '/path/:slug', headers: [ { key: 'Custom-Header', value: 'Custom-Header-Value', }, { key: 'Cache-Control', value: 'public, max-age=3600', }, ], }, ] }, // other configurations... }

`

40. What is the purpose of the next.config.js experimental property?

The experimental property in next.config.js serves two main purposes in Next.js:

Accessing and enabling pre-release features:

**Fine-tuning advanced capabilities:

41. How would you optimize the performance of a large-scale Next.js application?

Optimizing a large-scale Next.js application involves multiple strategies across rendering, code management, and asset delivery. Key Points:

42****.** What is the difference between redirects and rewrites in Next.js, and when would you use each?

Redirects and rewrites in Next.js are used to control how URLs behave, but they function differently.

**Redirects: Change the URL in the browser. They are used for permanent (301) or temporary (302) moves.

Example:

JavaScript `

module.exports = { async redirects() { return [ { source: '/old-blog', destination: '/new-blog', permanent: true, }, ]; }, };

`

In this example, When a user visits /old-blog, the browser URL changes to /new-blog, and search engines update their links accordingly.

**Rewrites: Keep the URL in the browser unchanged. They internally map a URL to a different page or API route.

Example:

JavaScript `

module.exports = { async rewrites() { return [ { source: '/about', destination: '/info', }, ]; }, };

`

In this example, When a user visits /about, the browser still shows /about, but Next.js internally renders content from /info. This is useful for clean URLs or proxying API requests.

43. How can you achieve dynamic route-based code splitting without using getServerSideProps in Next.js?

Here are effective ways to achieve dynamic route-based code splitting in Next.js without relying on getServerSideProps:

**Dynamic Imports with next/dynamic :

import dynamic from 'next/dynamic';

const BlogPost = dynamic(() => import('../components/BlogPost'), { loading: () =>

Loading post...

, });

function BlogPage({ postId }) { // ...fetch post data...

return <BlogPost post={postData} />;

}

export default BlogPage;

`

**Client-Side Rendering (CSR) with Router:

import { useRouter } from 'next/router';

function BlogPage() { const router = useRouter(); const { postId } = router.query;

// ...fetch post data based on postId...

return <div>...</div>;

}

export default BlogPage;

`

44. Describe scenarios where you would choose to use getStaticProps over getServerSideProps, and vice versa.

Choosing between getStaticProps and getServerSideProps depends on several factors in your Next.js application. Here's a breakdown of scenarios where each method shines:

**Choose getStaticProps when:

**Choose getServerSideProps when:

45. Explain the purpose of the next export command. When would you use it, and what are its limitations?

As of Next.js 12.2, the next export command has been deprecated. Static exports are now configured in next.config.js using the output: 'export' option. Understanding the old command can still be useful for older projects or migrations.

**Purpose:

**Use Cases:

**Limitations:

**Current Approach:

46. How can you implement authentication in Next.js? Compare JWT, NextAuth, and Firebase approaches.

Next.js does not include built-in authentication, but you can implement it using JWT, NextAuth, or Firebase.

**JWT (JSON Web Tokens):

**NextAuth.js:

**Firebase Authentication:

47. What is the significance of the _error.js and 404.js files in the pages directory, and how can they be customized for error handling in Next.js?

Here's an explanation of the _error.js and 404.js files in Next.js, along with how to customize them for effective error handling:1.

**1. _error.js:

**Purpose:

**Customization:

Example:

JavaScript `

import React from 'react';

export default function Error({ statusCode }) { return (

Something went wrong!

We're working on it. Please try again later.

{statusCode !== 404 && (

Status Code: {statusCode}

)}
); }

`

**2. 404.js:

**Purpose:

**Customization:

Example:

JavaScript `

import React from 'react';

export default function NotFound() { return (

Page Not Found

Sorry, the page you're looking for doesn't exist.

Try searching for what you need, or go back to the homepage.

); }

`

48. How can you implement conditional redirects in Next.js based on certain criteria, such as user authentication status or role?

Here are several methods to implement conditional redirects in Next.js based on criteria like authentication status or user roles:

**Redirects in getServerSideProps or getStaticProps :

export async function getServerSideProps(context) { const isAuthenticated = await checkAuth(context.req);

if (
    !isAuthenticated &&
    context.resolvedUrl !== '/login'
){
    context.res
        .writeHead(302, { Location: '/login' });
    context.res.end();
    return { props: {} };
}

// ...fetch data for authenticated users...

}

`

**Client-Side Redirects with useEffect and router.push :

import { useEffect } from 'react'; import { useRouter } from 'next/router';

function MyPage() { const router = useRouter();

useEffect(
    () => {
        const isAuthenticated = checkAuth();
        if (!isAuthenticated) {
            router.push('/login');
        }
    }, []);

// ...page content...

}

`

49. Explain the purpose of the publicRuntimeConfig and serverRuntimeConfig options in Next.js. How do they differ from regular environment variables?

Next.js provides two distinct options for configuring your application: publicRuntimeConfig and serverRuntimeConfig. They differ from regular environment variables in terms of accessibility and security. Let's explore each option:

**1. publicRuntimeConfig:

**2. serverRuntimeConfig:

**3. Differences from Environment Variables:

50. How can you implement custom error boundaries in a Next.js project to gracefully handle errors and prevent the entire application from crashing?

Here's how to implement custom error boundaries in Next.js to gracefully handle errors and enhance application resilience:

**1. Create a Custom Error Boundary Component:

import React from 'react';

class ErrorBoundary extends React.Component { constructor(props) { super(props); this.state = { hasError: false }; }

static getDerivedStateFromError(error) {
    return { hasError: true };
}

componentDidCatch(error, errorInfo) {
    // Optionally log the error or send 
    //it to an error reporting service
}

render() {
    if (this.state.hasError) {
        return <h1>Something went wrong.</h1>;
    }
    return this.props.children;
}

}

`

**2. Wrap Components with the Error Boundary:

`

**Key Points: