What's New in Next.js 15: A Deep Dive

Next.js 15: What's New?

Next.js 15 brings significant improvements to performance, developer experience, and introduces powerful new features. Let's explore what's new.

1. Turbopack Stable

The Rust-based bundler is now production-ready:

// next.config.js
module.exports = {
  experimental: {
    turbo: true  // Now stable!
  }
}

Benefits:

• 700x faster HMR than Webpack
• 10x faster production builds
• Reduced memory usage

2. Partial Prerendering

Mix static and dynamic content seamlessly:

// app/page.tsx
export default async function Page() {
  return (
    <div>
      <StaticHeader />
      <Suspense fallback={<Loading />}>
        <DynamicContent />
      </Suspense>
      <StaticFooter />
    </div>
  )
}

3. Enhanced Server Actions

Improved error handling and validation:

'use server'

import { z } from 'zod'

const schema = z.object({
  email: z.string().email(),
  name: z.string().min(2)
})

export async function createUser(formData: FormData) {
  const validated = schema.parse({
    email: formData.get('email'),
    name: formData.get('name')
  })
  
  // Type-safe data
  await db.user.create({ data: validated })
}

4. Improved Image Component

Better performance with built-in optimization:

import Image from 'next/image'

export default function Gallery() {
  return (
    <Image
      src="/hero.jpg"
      alt="Hero"
      width={800}
      height={400}
      priority
      placeholder="blur"
      blurDataURL={generateBlur()}
    />
  )
}

5. React 19 Support

Full compatibility with React 19 features:

// New use() hook
import { use } from 'react'

function Comments({ commentsPromise }) {
  const comments = use(commentsPromise)
  return <div>{/* Render comments */}</div>
}

6. Better Error Messages

More helpful development errors:

Error: Hydration failed because the initial UI does not match what was rendered on the server.

Expected: <div class="server-class">
Received: <div class="client-class">

Component Stack:
  Page (app/page.tsx:15)
  Layout (app/layout.tsx:8)

7. Metadata API Improvements

More flexible metadata handling:

export async function generateMetadata({ params }) {
  const post = await getPost(params.slug)
  
  return {
    title: post.title,
    openGraph: {
      images: [{ url: post.image }],
    },
    twitter: {
      card: 'summary_large_image',
    }
  }
}

Conclusion

Next.js 15 represents a major leap forward in performance and developer experience. The stable Turbopack alone makes upgrading worthwhile, and the new features open up exciting possibilities for building modern web applications.