Next.js 15 New Features: Complete Developer Guide

Next.js 15 brings revolutionary improvements to the React framework ecosystem. Here's everything you need to know about the latest features and how to leverage them in your SaaS applications.

Key New Features in Next.js 15

1. Turbopack Stable Release

Turbopack is now stable and production-ready:

# Enable Turbopack in development
next dev --turbo

Performance improvements:

• 95% faster local development server startup
• 68% faster HMR (Hot Module Replacement)
• Significantly reduced memory usage

2. Enhanced App Router

The App Router has been refined with better:

• Parallel Routes: Load multiple pages simultaneously
• Intercepting Routes: Modal-like experiences without navigation
• Route Groups: Organize routes without affecting URL structure

// app/@modal/(.)photos/[id]/page.tsx
export default function PhotoModal({ params }: { params: { id: string } }) {
  return <Modal photoId={params.id} />;
}

3. React Server Components Improvements

Server Components are now more powerful:

// Server Component with async data fetching
async function ProductList() {
  const products = await fetch("https://api.example.com/products");
  return (
    <div>
      {products.map((p) => (
        <ProductCard key={p.id} product={p} />
      ))}
    </div>
  );
}

4. Improved Caching Strategy

Next.js 15 introduces smarter caching:

• Automatic cache invalidation
• Better ISR (Incremental Static Regeneration)
• On-demand revalidation

// Revalidate on demand
import { revalidatePath } from 'next/cache';

export async function updateProduct(id: string) {
  // Update in database
  await db.product.update({ where: { id }, data: { ... } });

  // Revalidate the page
  revalidatePath(`/products/${id}`);
}

5. Server Actions Enhancements

Server Actions are now more intuitive:

"use server";

export async function createUser(formData: FormData) {
  const email = formData.get("email");
  const name = formData.get("name");

  await db.user.create({
    data: { email, name },
  });

  redirect("/dashboard");
}

Migration Guide

From Next.js 14 to 15

1. Update your dependencies:

npm install next@15 react@19 react-dom@19

2. Update next.config.js:

/** @type {import('next').NextConfig} */
const nextConfig = {
  experimental: {
    serverActions: true,
    turbo: true,
  },
};

module.exports = nextConfig;

3. Review breaking changes in the official documentation.

Best Practices for Next.js 15

1. Use Server Components by default - Only add 'use client' when necessary
2. Leverage streaming - Use Suspense for better loading states
3. Optimize images - Use the next/image component
4. Enable Turbopack - Faster development experience

Conclusion

Next.js 15 represents a significant leap forward for React developers. FastSaaS is built on Next.js 15, giving you access to all these features out of the box.

Get FastSaaS and start building with Next.js 15 today!