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Top 25 Next.js Interview Questions and Answers (2025 Guide)

June 29, 2025

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23 min read

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Introduction

Next.js has quickly become the reliable framework for building fast, scalable, and SEO-friendly React applications. With features like server-side rendering (SSR), static site generation (SSG), API routes, and the new App Router, it's no surprise that many companies are actively looking for developers who are comfortable working with Next.js.

If you're preparing for a frontend or full-stack developer role in 2025, understanding Next.js concepts is a must. Employers often include specific Next.js interview questions to test how well you understand both React and the underlying architecture of modern web apps.

In this blog, you'll find a list of Next.js interview questions and answers, ranging from beginner-level to advanced. Whether you're a fresher aiming to break into your first job or an experienced developer preparing for a senior-level role, these questions will help you crack interviews with confidence.

Beginner Level Next.js Interview Questions

These Next.js interview questions test your understanding of the fundamentals of Next.js. If you're new to the framework or applying for a junior frontend role, make sure you're comfortable with the basics listed below.

  1. What is Next.js and how is it different from React?

Next.js is a React-based framework for building web applications with features like server-side rendering, static site generation, and routing out of the box. While React is just a library for building UI components, Next.js provides a full-stack solution, including routing, API routes, and performance optimizations.

  1. What are the key features of Next.js?

    Some core features include:

    • File-based routing
    • Server-Side Rendering (SSR)
    • Static Site Generation (SSG)
    • Incremental Static Regeneration (ISR)
    • API Routes
    • Image Optimization
    • TypeScript support
    • Middleware and Edge functions

  2. What is file-based routing in Next.js?

In the latest Next.js, the app directory is used to define routes. Each file automatically becomes a route. For example, app/about/page.js becomes /about in the browser. This removes the need for external routing libraries like React Router.

  1. What are the differences between a page and a component in Next.js?

  • A page is a top-level file in the routing structure (app/page.js or pages/index.js) and is directly accessible via a route.
  • A component is a reusable piece of UI (e.g., a button or navbar) that can be imported and used inside pages or other components.

  1. What is the public/ folder used for in Next.js?

The public folder stores static assets like images, icons, or fonts. Files in this folder can be accessed directly using relative URLs (e.g., /logo.png). This is useful for assets that don't need processing or importing.

  1. What is a layout in the App Router?

In the App Router, a layout.js file is used to wrap all routes within a segment. It helps define consistent structure like headers, sidebars, or footers.

.tsx
1// app/layout.tsx
2export default function RootLayout({ children }) {
3return (
4  <html>
5    <body>{children}</body>
6  </html>
7);
8}

  1. How do you navigate between pages in Next.js?

Use the built-in Link component from next/link. It enables client-side navigation and prefetching.

.tsx
1import Link from 'next/link';
2
3<Link href="/about">Go to About</Link>

This improves performance by avoiding full page reloads.

These beginner Next.js interview questions form the foundation for understanding Next.js. You should know how routing works, how to structure files, and how to differentiate between components and pages. Once you're comfortable with these, move on to data fetching, middleware, and performance topics.

Intermediate-Level Next.js Interview Questions

Once you understand the basics of routing and pages in Next.js, interviewers often dive into core concepts that affect app performance, structure, and real-world use. These intermediate nextjs interview questions test how well you understand Next.js beyond the surface.

Below are some commonly asked Next.js interview questions for mid-level developers, with concise, clear answers.

  1. What is the difference between getStaticProps, getServerSideProps, and getStaticPaths?

These are data-fetching methods used in the Pages Router:

  • getStaticProps: Runs at build time for Static Site Generation (SSG).
  • getServerSideProps: Runs on each request for Server-Side Rendering (SSR).
  • getStaticPaths: Used with dynamic routes to define paths that should be statically generated.

In the App Router, these are replaced by async functions inside Server Components.

  1. How do you fetch data in the App Router?

In the App Router, you typically fetch data using async functions directly in Server Components:

.tsx
1// app/blog/page.tsx
2export default async function BlogPage() {
3const res = await fetch('https://api.example.com/posts');
4const posts = await res.json();
5
6return <PostList posts={posts} />;
7}

For client-side data fetching, use useEffect() or libraries like SWR or React Query.

Learn More about React Query

  1. How do dynamic routes work in Next.js App Router?

You define a folder with square brackets for dynamic segments:

.ssh
1app/blog/[slug]/page.tsx

Then, params.slug is available as a prop in your server component:

  1. What are API routes in Next.js?

API routes in Next.js allow you to create backend endpoints directly inside your Next.js app without setting up a separate server (like Express). These routes live inside the /app/api/ or /pages/api/ directory, depending on whether you're using the App Router or Pages Router.

.ts
1// app/api/hello/route.ts
2export function GET(req) {
3return new Response(JSON.stringify({ message: "Hello from API!" }), {
4  status: 200,
5});
6}

Key Points

  • API routes run only on the server, never exposed to the client.
  • They can use Node.js packages, access environment variables, and talk to databases.
  • They are deployed as serverless functions on platforms like Vercel.

  1. What is Incremental Static Regeneration (ISR)?

Incremental Static Regeneration (ISR) is a feature in Next.js that allows you to update static content after the site has been built, without rebuilding the entire app. It combines the performance of static generation with the flexibility of server rendering.

.tsx
1// app/blog/[slug]/page.js
2export default async function BlogPost({ params }) {
3const post = await fetch(`https://example.com/api/posts/${params.slug}`, {
4  next: { revalidate: 60 }, // Optional here, or use static export
5}).then(res => res.json());
6
7return (
8  <main>
9    <h1>{post.title}</h1>
10    <p>{post.content}</p>
11  </main>
12);
13}

  1. What is loading.js in App Router and how does it work?

In Next.js App Router, loading.js is a special file that allows you to show a loading UI (skeleton/spinner/placeholder) while your page or layout is fetching data asynchronously.

If your page component uses async/await:

.tsx
1// app/blog/[slug]/page.tsx
2export default async function BlogPost({ params }) {
3const data = await fetch(`https://api.example.com/posts/${params.slug}`).then(res => res.json());
4
5return <div>{data.title}</div>;
6}

Next.js automatically shows loading.js while this fetch is in progress.

Example of loading.js

.js
1// app/blog/[slug]/loading.js
2export default function Loading() {
3return (
4  <div className="animate-pulse">
5    <div className="h-6 bg-gray-300 rounded w-1/2 mb-4"></div>
6    <div className="h-4 bg-gray-200 rounded w-full"></div>
7    <div className="h-4 bg-gray-200 rounded w-full mt-2"></div>
8  </div>
9);
10}

This will be rendered only during loading of that route's page/layout.

  1. What is Middleware in Next.js and how is it used?

Middleware in Next.js lets you run code before a request is completed, right in the edge runtime (very fast). It's useful for tasks like:

  • Authentication
  • Redirects
  • A/B testing
  • Geo-based content
  • Logging or analytics

It runs before rendering a page or API route and gives you control over the request/response cycle.

Basic Example

Create a file named middleware.js or middleware.ts in your project root:

.js
1// middleware.js
2import { NextResponse } from 'next/server';
3
4export function middleware(request) {
5const loggedIn = request.cookies.get('token');
6
7if (!loggedIn) {
8  return NextResponse.redirect(new URL('/login', request.url));
9}
10
11return NextResponse.next(); // Continue to requested page
12}

In this example:

  • If a user is not logged in, they are redirected to /login.
  • If logged in, the request continues normally.

Advanced Next.js Interview Questions

For senior roles or complex projects, interviewers expect deep knowledge of Next.js internals, rendering strategies, and scalable app design. These advanced nextjs interview questions go beyond syntax and focus on performance, architecture, and real-world implementation patterns.

Here are the top Next.js advanced interview questions, with clear and insightful answers.

  1. What are React Server Components and how do they work in Next.js?

React Server Components (RSCs) are components that render on the server and send serialized HTML to the client without bundling JavaScript. Next.js integrates RSCs in the App Router by default. Any component without 'use client' runs on the server.

Benefits:

  • Zero JS sent to client (for server-only components)
  • Smaller client bundles
  • Faster load times

  1. What is streaming in Next.js, and how does it improve performance?

Streaming allows Next.js to send HTML to the browser in chunks before the full page is ready. Used in App Router with layouts and loading.js, it improves Time To First Byte (TTFB) and perceived performance.

Example: You can show a loading UI while a slow data-fetching component loads in the background.

  1. How does Next.js handle SEO optimization?

Next.js supports server-side rendering (SSR), which improves SEO by sending fully rendered HTML to crawlers.

Key SEO features:

  • Custom robots.txt and sitemap.xml
  • Dynamic meta using generateMetadata() in App Router
  • Clean URL structure via file-based routing
  • Pre-rendering content (SSG/SSR)

  1. How do you dynamically generate metadata in the App Router?

Use generateMetadata() in a Server Component:

.tsx
1export async function generateMetadata({ params }) {
2const post = await getPost(params.slug);
3return {
4  title: post.title,
5  description: post.summary,
6};
7}

This enables dynamic <title> and <meta> tags for SEO.

Learn Complete SEO in Next.js.

  1. How does Next.js handle images and why is it better than <img>?

Next.js provides an optimized <Image /> component through its built-in Image Optimization API. It offers advanced performance features that are not available with the standard HTML <img> tag.

You import it from next/image:

.tsx
1import Image from 'next/image';
2
3export default function MyComponent() {
4return (
5  <Image
6    src="/profile.jpg"
7    alt="Profile Picture"
8    width={300}
9    height={300}
10  />
11);
12}

Next.js provides the <Image /> component with built-in features like:

  • Lazy loading
  • Responsive image sizes
  • WebP conversion
  • Automatic optimization

This improves performance, Core Web Vitals, and bandwidth usage.

  1. How would you handle environment variables in a Next.js application?

Environment variables store sensitive or environment-specific configuration, such as:

  • API keys
  • Database credentials
  • Base URLs
  • Feature flags Handling environment variables in a Next.js application is straightforward and secure if done correctly.

Creating an Environment Variable

.env
1# .env.local
2NEXT_PUBLIC_API_URL=https://api.example.com
3SECRET_KEY=super_secret_value

Accessing Environment Variables

On the client:

.tsx
1const apiUrl = process.env.NEXT_PUBLIC_API_URL;

On the server:

.ts
1const secret = process.env.SECRET_KEY;

Frequently Asked Questions

  • Q: Do I need to learn the App Router or Pages Router for interviews?

    A: Learn both if possible, but prioritize the App Router for modern projects (Next.js 13+). However, many legacy projects still use the Pages Router, so understanding both is helpful.

  • Q: Can I be asked about deployment in a Next.js interview?

    A: Yes. You may be asked how to deploy on platforms like Vercel, custom VPS, or Netlify, including how to handle environment variables and production builds.

Learn How to deploy Next.js on VPS

  • Q: Is TypeScript important in Next.js interviews?

    A: Increasingly yes. Many companies use TypeScript with Next.js, especially in production. You may be asked to type props, API responses, or refactor JavaScript code to TypeScript.

  • Q: Will I be asked to write code in a Next.js interview?

    A: Often yes. You may be asked to build a small component, set up a route, protect a page, or fetch data using SSR/ISR. Be ready for hands-on coding or take-home tasks.

Conclusion

Next.js has become one of the most in-demand frameworks for building high-performance, full-stack web applications. Whether you're preparing for a frontend role, a full-stack position, or a senior-level interview, understanding how Next.js works — from routing and layouts to data fetching and server components — is crucial.

By preparing with these Next.js interview questions and practicing real-world scenarios, you'll be well-equipped to confidently tackle any Next.js-related interview in 2025 and beyond.

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