Next.js 15: What's New and Should You Upgrade?

Next.js 15 is a significant release — not because it introduces revolutionary new concepts, but because it takes the experimental features of Next 13 and 14 and makes them production-ready and coherent. After two years of App Router growing pains, Next.js 15 is the version that makes the new paradigm feel stable and trustworthy.

The Biggest Changes

• <strong>Turbopack is now stable for development.</strong> Up to 76.7% faster Fast Refresh and 96.3% faster initial compile time compared to Webpack. Finally.
• <strong>Async Request APIs.</strong> cookies(), headers(), and params are now async. Breaking change, but the right architectural decision for streaming.
• <strong>Partial Prerendering (PPR) in stable.</strong> Serve a static shell instantly, then stream dynamic content. The best of static and dynamic in one page.
• <strong>Improved caching defaults.</strong> fetch() requests and GET Route Handlers are no longer cached by default — a hugely welcome fix that eliminates a major source of confusion.
• <strong>React 19 support.</strong> Full support for concurrent features, the new form actions API, and use() hook.

Partial Prerendering: The Game Changer

import { Suspense } from 'react';
import { StaticHero } from './StaticHero';  // rendered at build time
import { DynamicFeed } from './DynamicFeed'; // streamed per-request

// Enable PPR for this route
export const experimental_ppr = true;

export default function Dashboard() {
  return (
    <main>
      {/* Served from cache instantly */}
      <StaticHero />

      {/* Streamed from server — no full-page delay */}
      <Suspense fallback={<FeedSkeleton />}>
        <DynamicFeed />
      </Suspense>
    </main>
  );
}

Should You Upgrade Now?

Yes, for new projects — absolutely. For existing projects: if you're on Next.js 14 with the App Router, the migration is straightforward. The main breaking change is the async Request APIs. Run the provided codemod (npx @next/codemod@latest upgrade latest) and it handles 90% of the changes automatically. If you're on Pages Router (Next 12/13), there's no rush — Pages Router is fully supported and stable.