React.js vs Next.js: A Complete Comparison for 2025

What is React.js?

React is a lightweight JavaScript library for building user interfaces. It focuses on components and client-side rendering (CSR) and is great for single-page apps (SPAs), dashboards, or when you want full control over tooling.

What is Next.js?

Next.js is a full framework built on React that adds server-side rendering (SSR), static-site generation (SSG), file-based routing, image optimization, and API routes. It is ideal for SEO-focused websites, blogs, and e-commerce.

Quick Comparison

Feature	React.js	Next.js
Type	UI Library	Framework
Routing	React Router/custom	File-based (built-in)
Rendering	CSR	CSR, SSR, SSG, ISR
SEO	Extra setup needed	SEO-friendly by default

Short Code Examples

React (CSR) — App.jsx

import React from 'react';

export default function App() {
  return <div>Hello from React (CSR)</div>;
}
  

Next.js (SSR) — pages/index.js

export async function getServerSideProps() {
  const res = await fetch('https://api.example.com/posts');
  const posts = await res.json();
  return { props: { posts } };
}

export default function Home({ posts }) {
  return <div>Posts: {posts.length}</div>;
}
  

When to Choose Which

• Use React: Internal tools, dashboards, SPAs, when SEO is not a priority.
• Use Next.js: Blogs, e-commerce, marketing sites, or when SEO and fast first paint matter.

Conclusion

Learn React first to understand components and hooks. Next.js is often the better choice for production apps where SEO, performance, and developer productivity matter.

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