Next.js 15: The Complete Guide to React's Most Powerful Framework

Next.js has revolutionized how we build React applications, and with the release of Next.js 15 (and the latest 15.5), the framework reaches new heights of performance, developer experience, and functionality. Whether you're building a simple blog or a complex enterprise application, Next.js 15 provides everything you need out of the box.

In this comprehensive guide, we'll explore everything from installation to advanced features, including how to leverage Markdown rendering for blog posts like this one!

What's New in Next.js 15?

Next.js 15, released in October 2024 and continuously updated through 2025, brings groundbreaking improvements that make it the most powerful version yet.

🚀 React 19 Support

Next.js 15.1 introduced stable support for React 19, bringing cutting-edge React features to your applications:

jsxCopy
// React 19 features now work seamlessly in Next.js 15
import { use } from 'react';

export default function UserProfile({ userPromise }) {
  // New 'use' hook for handling promises
  const user = use(userPromise);

  return (
    <div className="profile">
      <h1>{user.name}</h1>
      <p>{user.email}</p>
    </div>
  );
}

⚡ Turbopack: Lightning-Fast Development

Turbopack, the Rust-based successor to Webpack, delivers incredible performance improvements:

• 75% faster local server startup
• 95% faster code updates with Fast Refresh
• Built in Rust for maximum performance

bashCopy
# Enable Turbopack for development
next dev --turbo

# With Turbopack, you'll see speeds like:
# ✓ Ready in 1.2s (previously 5s)
# ✓ Fast Refresh in 50ms (previously 1s)

Benchmark Results (on Vercel app):

Traditional Webpack:
├── Initial compile: 5.2s
├── Fast Refresh: 980ms
└── Bundle time: 12.4s

Turbopack (75-95% faster):
├── Initial compile: 1.3s
├── Fast Refresh: 49ms
└── Bundle time: 3.1s

📝 New Form Component

The new <Form> component extends HTML forms with Next.js superpowers:

tsxCopy
import Form from 'next/form';

export default function SearchPage() {
  return (
    <Form action="/search">
      {/* Prefetching for instant navigation */}
      <input name="query" placeholder="Search..." />
      <button type="submit">Search</button>
    </Form>
  );
}

Features:

• Automatic prefetching of the target route
• Client-side navigation with progressive enhancement
• Falls back to native form submission if JavaScript fails

🔄 Asynchronous Request APIs

Next.js 15 introduces async versions of dynamic APIs for better data fetching:

typescriptCopy
// Before (Next.js 14)
import { cookies } from 'next/headers';

export default function Page() {
  const cookieStore = cookies();
  const theme = cookieStore.get('theme');
  return <div>Theme: {theme}</div>;
}

// After (Next.js 15)
import { cookies } from 'next/headers';

export default async function Page() {
  const cookieStore = await cookies();
  const theme = cookieStore.get('theme');
  return <div>Theme: {theme}</div>;
}

Async APIs now include:

• cookies() - Read request cookies
• headers() - Access request headers
• params - Dynamic route parameters
• searchParams - URL search parameters

🛡️ Enhanced Error Handling

The new onRequestError hook captures errors and sends them to your observability provider:

typescriptCopy
// instrumentation.ts
export async function onRequestError(
  err: Error,
  request: Request,
  context: {
    routerKind: 'Pages Router' | 'App Router';
    routePath: string;
    routeType: 'render' | 'route' | 'action' | 'middleware';
  }
) {
  // Send to your error tracking service
  await fetch('https://your-error-tracker.com/api/errors', {
    method: 'POST',
    body: JSON.stringify({
      message: err.message,
      stack: err.stack,
      url: request.url,
      route: context.routePath,
      type: context.routeType,
      timestamp: new Date().toISOString(),
    }),
  });
}

📘 TypeScript Improvements (15.5)

Next.js 15.5 introduces stable typed routes for compile-time type safety:

typescriptCopy
// next.config.ts
const config: NextConfig = {
  experimental: {
    typedRoutes: true, // Now stable!
  },
};

export default config;

tsxCopy
import Link from 'next/link';

export default function Navigation() {
  return (
    <nav>
      {/* ✅ TypeScript knows this route exists */}
      <Link href="/blog/nextjs-15">Next.js Guide</Link>

      {/* ❌ TypeScript error: Route doesn't exist */}
      <Link href="/non-existent-route">Broken Link</Link>

      {/* ✅ Type-safe dynamic routes */}
      <Link
        href={{
          pathname: '/blog/[slug]',
          params: { slug: 'nextjs-15' }
        }}
      >
        Dynamic Route
      </Link>
    </nav>
  );
}

Getting Started with Next.js 15

Installation

Creating a new Next.js 15 project is simple:

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# Create a new Next.js app
npx create-next-app@latest my-nextjs-app

# You'll be prompted with:
# ✔ Would you like to use TypeScript? Yes
# ✔ Would you like to use ESLint? Yes
# ✔ Would you like to use Tailwind CSS? Yes
# ✔ Would you like to use `src/` directory? Yes
# ✔ Would you like to use App Router? Yes
# ✔ Would you like to use Turbopack for `next dev`? Yes

cd my-nextjs-app
npm run dev

Upgrading from Next.js 14

If you have an existing project:

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# Update Next.js
npm install next@latest react@latest react-dom@latest

# Check for breaking changes
npm run build

# Enable Turbopack
# Update package.json:
{
  "scripts": {
    "dev": "next dev --turbo"
  }
}

Project Structure

A typical Next.js 15 project looks like this:

my-nextjs-app/
├── src/
│   ├── app/                    # App Router (recommended)
│   │   ├── layout.tsx         # Root layout
│   │   ├── page.tsx           # Home page
│   │   ├── globals.css        # Global styles
│   │   ├── blog/
│   │   │   ├── page.tsx       # Blog list
│   │   │   └── [slug]/
│   │   │       └── page.tsx   # Blog post
│   │   └── api/
│   │       └── hello/
│   │           └── route.ts   # API endpoint
│   ├── components/            # Reusable components
│   └── lib/                   # Utility functions
├── public/                    # Static assets
├── content/                   # Markdown files
│   └── blog/
│       └── my-post.md
├── next.config.ts            # Next.js configuration
├── tsconfig.json             # TypeScript config
└── package.json

Building a Blog with Markdown Rendering

One of Next.js 15's powerful features is seamless Markdown rendering. Here's how to build a blog like the one you're reading!

Step 1: Install Dependencies

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npm install gray-matter remark remark-html
npm install react-syntax-highlighter @types/react-syntax-highlighter
npm install reading-time

Step 2: Create Blog Post Structure

Create markdown files in content/blog/:

markdownCopy
---
title: "My First Blog Post"
excerpt: "Learn how to build a blog with Next.js 15"
category: "tutorial"
date: "2025-11-22"
readTime: "5 min read"
tags: ["Next.js", "React", "Markdown"]
author: "Your Name"
---

# My First Blog Post

This is the content of my blog post written in **Markdown**!

## Code Example

```javascript
console.log('Hello, Next.js 15!');

### Step 3: Create Markdown Parser

```typescript
// src/lib/markdown.ts
import fs from 'fs';
import path from 'path';
import matter from 'gray-matter';
import { remark } from 'remark';
import html from 'remark-html';

const postsDirectory = path.join(process.cwd(), 'content/blog');

export interface BlogPost {
  slug: string;
  title: string;
  excerpt: string;
  category: string;
  date: string;
  readTime: string;
  tags: string[];
  author: string;
  content: string;
}

export async function getPost(slug: string): Promise<BlogPost> {
  const fullPath = path.join(postsDirectory, `${slug}.md`);
  const fileContents = fs.readFileSync(fullPath, 'utf8');

  // Parse markdown frontmatter
  const { data, content } = matter(fileContents);

  // Convert markdown to HTML
  const processedContent = await remark()
    .use(html)
    .process(content);

  return {
    slug,
    content: processedContent.toString(),
    ...data,
  } as BlogPost;
}

export function getAllPosts(): Array<Omit<BlogPost, 'content'>> {
  const fileNames = fs.readdirSync(postsDirectory);

  const posts = fileNames
    .filter(fileName => fileName.endsWith('.md'))
    .map(fileName => {
      const slug = fileName.replace(/\.md$/, '');
      const fullPath = path.join(postsDirectory, fileName);
      const fileContents = fs.readFileSync(fullPath, 'utf8');
      const { data } = matter(fileContents);

      return {
        slug,
        ...data,
      } as Omit<BlogPost, 'content'>;
    })
    .sort((a, b) => (a.date > b.date ? -1 : 1));

  return posts;
}

Step 4: Create Blog List Page

tsxCopy
// src/app/blog/page.tsx
import Link from 'next/link';
import { getAllPosts } from '@/lib/markdown';

export default async function BlogPage() {
  const posts = getAllPosts();

  return (
    <div className="container mx-auto px-4 py-16">
      <h1 className="text-4xl font-bold mb-8">Blog</h1>

      <div className="grid gap-8 md:grid-cols-2 lg:grid-cols-3">
        {posts.map((post) => (
          <Link
            key={post.slug}
            href={`/blog/${post.slug}`}
            className="group block p-6 bg-white rounded-lg shadow-lg
                     hover:shadow-xl transition-shadow"
          >
            <div className="flex gap-2 mb-3">
              {post.tags.map((tag) => (
                <span
                  key={tag}
                  className="text-xs px-2 py-1 bg-blue-100
                           text-blue-800 rounded"
                >
                  {tag}
                </span>
              ))}
            </div>

            <h2 className="text-2xl font-bold mb-2 group-hover:text-blue-600
                         transition-colors">
              {post.title}
            </h2>

            <p className="text-gray-600 mb-4">{post.excerpt}</p>

            <div className="flex justify-between text-sm text-gray-500">
              <span>{post.date}</span>
              <span>{post.readTime}</span>
            </div>
          </Link>
        ))}
      </div>
    </div>
  );
}

Step 5: Create Blog Post Page with Syntax Highlighting

tsxCopy
// src/app/blog/[slug]/page.tsx
import { notFound } from 'next/navigation';
import { getPost, getAllPosts } from '@/lib/markdown';
import ReactMarkdown from 'react-markdown';
import { Prism as SyntaxHighlighter } from 'react-syntax-highlighter';
import { vscDarkPlus } from 'react-syntax-highlighter/dist/esm/styles/prism';

export async function generateStaticParams() {
  const posts = getAllPosts();
  return posts.map((post) => ({
    slug: post.slug,
  }));
}

export default async function BlogPostPage({
  params,
}: {
  params: { slug: string };
}) {
  const post = await getPost(params.slug);

  if (!post) {
    notFound();
  }

  return (
    <article className="container mx-auto px-4 py-16 max-w-4xl">
      {/* Header */}
      <header className="mb-12">
        <div className="flex gap-2 mb-4">
          {post.tags.map((tag) => (
            <span
              key={tag}
              className="text-xs px-3 py-1 bg-blue-100
                       text-blue-800 rounded-full"
            >
              {tag}
            </span>
          ))}
        </div>

        <h1 className="text-5xl font-bold mb-4">{post.title}</h1>

        <div className="flex items-center gap-4 text-gray-600">
          <span>{post.author}</span>
          <span>•</span>
          <span>{post.date}</span>
          <span>•</span>
          <span>{post.readTime}</span>
        </div>
      </header>

      {/* Content with Syntax Highlighting */}
      <div className="prose prose-lg max-w-none">
        <ReactMarkdown
          components={{
            code({ node, inline, className, children, ...props }) {
              const match = /language-(\w+)/.exec(className || '');

              return !inline && match ? (
                <SyntaxHighlighter
                  style={vscDarkPlus}
                  language={match[1]}
                  PreTag="div"
                  {...props}
                >
                  {String(children).replace(/\n$/, '')}
                </SyntaxHighlighter>
              ) : (
                <code className={className} {...props}>
                  {children}
                </code>
              );
            },
          }}
        >
          {post.content}
        </ReactMarkdown>
      </div>
    </article>
  );
}

Advanced Features & Best Practices

1. Server Components by Default

All components in the App Router are Server Components by default:

tsxCopy
// This runs on the server - no JavaScript sent to client!
export default async function UserDashboard() {
  const data = await fetch('https://api.example.com/user', {
    cache: 'no-store', // Dynamic data
  });

  const user = await data.json();

  return (
    <div>
      <h1>Welcome, {user.name}</h1>
      <UserStats stats={user.stats} />
    </div>
  );
}

2. Client Components for Interactivity

Use 'use client' for interactive components:

tsxCopy
'use client';

import { useState } from 'react';

export default function Counter() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>
        Increment
      </button>
    </div>
  );
}

3. Data Fetching Patterns

typescriptCopy
// Static data (generated at build time)
async function getStaticData() {
  const res = await fetch('https://api.example.com/posts', {
    cache: 'force-cache', // Default behavior
  });
  return res.json();
}

// Dynamic data (fetched on each request)
async function getDynamicData() {
  const res = await fetch('https://api.example.com/user', {
    cache: 'no-store',
  });
  return res.json();
}

// Revalidated data (cached with time-based revalidation)
async function getRevalidatedData() {
  const res = await fetch('https://api.example.com/products', {
    next: { revalidate: 3600 }, // Revalidate every hour
  });
  return res.json();
}

4. Metadata API

typescriptCopy
import type { Metadata } from 'next';

export const metadata: Metadata = {
  title: 'Next.js 15 Guide',
  description: 'Learn everything about Next.js 15',
  openGraph: {
    title: 'Next.js 15 Guide',
    description: 'Learn everything about Next.js 15',
    images: ['/og-image.jpg'],
  },
  twitter: {
    card: 'summary_large_image',
    title: 'Next.js 15 Guide',
    description: 'Learn everything about Next.js 15',
    images: ['/og-image.jpg'],
  },
};

5. Loading States

tsxCopy
// app/blog/loading.tsx
export default function Loading() {
  return (
    <div className="container mx-auto px-4 py-16">
      <div className="animate-pulse">
        <div className="h-8 bg-gray-200 rounded w-1/4 mb-8"></div>
        <div className="grid gap-8 md:grid-cols-3">
          {[...Array(6)].map((_, i) => (
            <div key={i} className="bg-gray-100 p-6 rounded-lg">
              <div className="h-4 bg-gray-200 rounded mb-4"></div>
              <div className="h-4 bg-gray-200 rounded mb-4"></div>
              <div className="h-4 bg-gray-200 rounded w-2/3"></div>
            </div>
          ))}
        </div>
      </div>
    </div>
  );
}

Performance Optimization

Image Optimization

tsxCopy
import Image from 'next/image';

export default function Hero() {
  return (
    <Image
      src="/hero.jpg"
      alt="Hero image"
      width={1200}
      height={600}
      priority // Load immediately for above-the-fold images
      placeholder="blur" // Show blur while loading
      blurDataURL="data:image/jpeg;base64,/9j/4AAQSkZJRg..."
    />
  );
}

Font Optimization

tsxCopy
import { Inter, Roboto_Mono } from 'next/font/google';

const inter = Inter({
  subsets: ['latin'],
  display: 'swap',
});

const robotoMono = Roboto_Mono({
  subsets: ['latin'],
  display: 'swap',
});

export default function RootLayout({ children }) {
  return (
    <html lang="en" className={inter.className}>
      <body>{children}</body>
    </html>
  );
}

Bundle Analysis

typescriptCopy
// next.config.ts
const config: NextConfig = {
  // Enable bundle analysis
  bundlePagesRouterDependencies: true,

  // Optimize packages
  transpilePackages: ['@my-org/ui'],

  // Enable production optimizations
  compiler: {
    removeConsole: process.env.NODE_ENV === 'production',
  },
};

Testing Your Syntax Highlighting

Let's test various programming languages to ensure the syntax highlighting works:

JavaScript/TypeScript

javascriptCopy
const greet = (name) => {
  console.log(`Hello, ${name}!`);
  return `Welcome to Next.js 15`;
};

// Array methods
const numbers = [1, 2, 3, 4, 5];
const doubled = numbers.map(n => n * 2);

Python

pythonCopy
def fibonacci(n):
    """Generate Fibonacci sequence"""
    if n <= 1:
        return n
    else:
        return fibonacci(n-1) + fibonacci(n-2)

# List comprehension
squares = [x**2 for x in range(10)]

CSS

cssCopy
.container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  padding: 2rem;
}

.card {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  border-radius: 0.5rem;
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
  transition: transform 0.3s ease;
}

.card:hover {
  transform: translateY(-5px);
}

JSON

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{
  "name": "my-nextjs-app",
  "version": "1.0.0",
  "scripts": {
    "dev": "next dev --turbo",
    "build": "next build",
    "start": "next start"
  },
  "dependencies": {
    "next": "^15.5.0",
    "react": "^19.0.0"
  }
}

Bash

bashCopy
#!/bin/bash

# Deploy script
echo "Deploying Next.js app..."

npm run build
npm run test

if [ $? -eq 0 ]; then
    echo "✓ Build successful"
    npm run deploy
else
    echo "✗ Build failed"
    exit 1
fi

Deployment

Vercel (Recommended)

bashCopy
# Install Vercel CLI
npm i -g vercel

# Deploy
vercel

# Production deployment
vercel --prod

Docker

dockerfileCopy
# Dockerfile
FROM node:18-alpine AS base

# Dependencies
FROM base AS deps
WORKDIR /app
COPY package*.json ./
RUN npm ci

# Builder
FROM base AS builder
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
RUN npm run build

# Runner
FROM base AS runner
WORKDIR /app
ENV NODE_ENV production

COPY --from=builder /app/public ./public
COPY --from=builder /app/.next/standalone ./
COPY --from=builder /app/.next/static ./.next/static

EXPOSE 3000
ENV PORT 3000

CMD ["node", "server.js"]

Self-Hosted

bashCopy
# Build for production
npm run build

# Start production server
npm start

# Or use PM2
pm2 start npm --name "nextjs-app" -- start

Migration Tips

From Next.js 14 to 15

1. Update Dependencies

bashCopy
npm install next@latest react@latest react-dom@latest

2. Async Request APIs

typescriptCopy
// Update dynamic API calls to async
const cookieStore = await cookies();
const headersList = await headers();

3. Enable Turbopack

jsonCopy
{
  "scripts": {
    "dev": "next dev --turbo"
  }
}

4. Test Thoroughly

bashCopy
npm run build
npm run start

Conclusion

Next.js 15 represents a massive leap forward in web development. With React 19 support, Turbopack's blazing-fast performance, enhanced TypeScript support, and powerful new features like the Form component and async request APIs, it's the perfect framework for building modern web applications.

The combination of:

• ⚡ Performance: Turbopack makes development incredibly fast
• 🎯 Type Safety: Typed routes catch errors before deployment
• 📝 Developer Experience: Better error handling and debugging
• 🚀 Modern React: Full React 19 support with latest features
• 📦 Flexibility: Works for everything from blogs to enterprise apps

...makes Next.js 15 the best version yet.

Whether you're building a personal blog with Markdown rendering (like this post!), an e-commerce platform, or a complex dashboard, Next.js 15 provides all the tools you need to build fast, scalable, production-ready applications.

Ready to Build with Next.js 15?

At Joulyan IT, we specialize in building high-performance web applications using cutting-edge technologies like Next.js 15. From planning to deployment, we help businesses leverage the latest web technologies to create exceptional user experiences.

Want to discuss your next project? Contact us to learn how we can help bring your vision to life with Next.js 15.

---

Sources

• Next.js 15 | Next.js
• Next.js 15.5 | Next.js
• What's New in Next.js 15: New Hooks, Turbopack and more - DEV Community
• Next.js 15.3 Release: New Features, Improvements & Tips | Medium
• Releases · vercel/next.js

---

Last updated: November 22, 2025