What is Next.js? A Complete Guide for Beginners

Next.js is a modern web development framework built on top of React.js, designed to enable developers to build high-performance, production-ready applications with ease. Developed and maintained by Vercel, Next.js extends React's capabilities by offering powerful features such as server-side rendering (SSR), static site generation (SSG), API routes, image optimization, and automatic code splitting.

In this article, we'll explore what makes Next.js unique, its key features, and why it's a top choice for building web applications in 2025.

Why Use Next.js?

React is great for building user interfaces, but on its own, it lacks certain critical features needed for production apps—such as routing, server-side rendering, and performance optimization. That’s where Next.js comes in.

Next.js provides:

  • A built-in file-based routing system
  • Optimized rendering strategies
  • Enhanced SEO support
  • Full-stack capabilities (frontend + backend)

Key Features of Next.js

1. File-Based Routing

In Next.js, every file in the pages/ directory automatically becomes a route.

/pages/index.js     →  '/'
/pages/about.js     →  '/about'
/pages/blog/[id].js →  '/blog/:id'

This simplifies navigation and eliminates the need for additional routing libraries like react-router.

2. Pre-Rendering: SSR and SSG

Next.js supports two main pre-rendering methods:

Server-Side Rendering (SSR) - Pages are generated at request time on the server.

export async function getServerSideProps(context) {
  return { props: { data: 'SSR content' } }
}

Static Site Generation (SSG) - Pages are generated at build time.

export async function getStaticProps() {
  return { props: { data: 'SSG content' } }
}

This improves performance, SEO, and initial page load speed.

3. API Routes

With API routes in the pages/api/ directory, you can build backend functionality directly in your Next.js app no need for a separate server.

// pages/api/hello.js
export default function handler(req, res) {
  res.status(200).json({ message: 'Hello from API' })
}

4. Image Optimization

The built-in next/image component provides:

  • Automatic image resizing
  • Lazy loading
  • WebP support
import Image from 'next/image'
<Image src="/logo.png" alt="Logo" width={200} height={100} />

5. Built-in CSS and Sass Support

You can use global CSS, component-level CSS Modules, or even Sass out of the box—no extra config needed.

6. Middleware & Edge Functions

Next.js 13+ introduces Middleware and Edge Functions, allowing you to run serverless logic closer to the user for tasks like authentication, redirects, and localization.

How Next.js Works Under the Hood

Next.js compiles pages on-demand (in SSR) or at build time (in SSG). It uses Webpack and Babel under the hood and provides automatic code splitting—only the required JavaScript is loaded for each page.

When Should You Use Next.js?

Next.js is a great fit for:

  • SEO-friendly websites (blogs, marketing pages)
  • E-commerce platforms
  • Dashboards or internal tools
  • Hybrid apps that need both static and dynamic content
  • Full-stack React applications with built-in APIs

Companies Using Next.js

Many major companies use Next.js in production, including: Twitch, Nike, Netflix Jobs, TikTok, HashiCorp, Hulu.

Next.js vs Other Frameworks

Feature React (CRA) Next.js Gatsby
Server-Side Rendering ❌ ✅ ✅ (limited)
Static Generation ⚠️ (manual setup) ✅ ✅
Routing Manual Automatic Automatic
API Routes ❌ ✅ ⚠️ (via plugins)
Image Optimization ❌ ✅ ✅

Conclusion

Next.js is more than just a React framework—it's a full-fledged toolkit for building modern web applications with a focus on performance, scalability, and developer experience.

Whether you're building a simple blog or a complex full-stack app, Next.js gives you everything you need, out of the box.

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