Welcome to Next.js! This comprehensive guide will help you understand the fundamentals of Next.js, one of the most popular React frameworks for building modern web applications.
What is Next.js?
Next.js is a React framework that makes building full-stack web applications easier. It provides a great developer experience with features like file-based routing, built-in optimization, and API routes. Whether you're building a simple blog or a complex enterprise application, Next.js provides the tools you need.
Why Choose Next.js?
- File-based Routing: Automatic page routing based on your file structure
- Built-in Optimization: Automatic image optimization and code splitting
- API Routes: Create backend endpoints without a separate server
- Full-Stack Capabilities: Write frontend and backend in the same project
- Deployment: Easy deployment to Vercel and other platforms
Core Concepts
1. File-Based Routing
Next.js uses a file-based routing system. Files in the app directory automatically become routes:
app/
├── page.tsx → /
├── about/
│ └── page.tsx → /about
└── blog/
└── [slug]/
└── page.tsx → /blog/:slug2. Server and Client Components
Next.js 13+ uses React Server Components by default. Use "use client" at the top of a file to make it a client component:
// Server Component (default)
export default function Page() {
const data = await fetchData() // Can use async
return <div>{data}</div>
}
// Client Component
"use client"
import { useState } from "react"
export default function Counter() {
const [count, setCount] = useState(0)
return <button onClick={() => setCount(count + 1)}>{count}</button>
}3. Rendering Strategies
Next.js supports multiple rendering strategies:
- Static Generation (SSG): Build-time rendering for fast, cacheable pages
- Server-Side Rendering (SSR): Render on each request for dynamic content
- Incremental Static Regeneration (ISR): Update static content without full rebuild
- Client-Side Rendering (CSR): Traditional browser rendering with JavaScript
Building Your First Next.js App
Step 1: Create a New Project
npx create-next-app@latest my-app
cd my-app
npm run devStep 2: Create a Page
// app/hello/page.tsx
export default function Hello() {
return (
<div className="p-8">
<h1 className="text-3xl font-bold">Hello, World!</h1>
<p>This is your first Next.js page.</p>
</div>
)
}Step 3: Add Navigation
// app/layout.tsx
import Link from "next/link"
export default function RootLayout({
children,
}: {
children: React.ReactNode
}) {
return (
<html>
<body>
<nav className="flex gap-4 p-4">
<Link href="/">Home</Link>
<Link href="/hello">Hello</Link>
</nav>
{children}
</body>
</html>
)
}API Routes
Create backend endpoints without a separate server:
// app/api/hello/route.ts
export async function GET() {
return Response.json({ message: "Hello from API" })
}
export async function POST(request: Request) {
const data = await request.json()
return Response.json({ received: data })
}Performance Optimization
Image Optimization
Use Next.js Image component for automatic optimization:
import Image from "next/image"
export default function Hero() {
return (
<Image
src="/hero.jpg"
alt="Hero"
width={1200}
height={600}
priority
/>
)
}Dynamic Imports
Load components only when needed:
import dynamic from "next/dynamic"
const HeavyComponent = dynamic(
() => import("@/components/heavy"),
{ loading: () => <p>Loading...</p> }
)Common Mistakes to Avoid
- Using async/await directly in Client Components: Server Components only
- Not using Next/Link for navigation: Use Link for client-side routing
- Forgetting to add alt text to images: Essential for accessibility
- Not optimizing images: Always use the Image component
- Storing secrets in environment variables: Use .env.local, never commit secrets
Deployment
Deploy your Next.js app to Vercel (recommended) or other platforms:
// Push to GitHub
git push origin main
// Vercel automatically deploys from main branch
// Your app is live!Conclusion
You now have a solid foundation in Next.js fundamentals! Start building real-world projects to deepen your understanding. Next.js combines the best of React with server-side capabilities, making it the perfect choice for modern web development.
Continue learning with our advanced Next.js courses covering topics like authentication, databases, and deployment strategies.