Next.js 15: React 19 Support, Async Request APIs, and Turbopack Stable

Vercel has released Next.js 15, a major update that completes the transition to React 19, stabilises the Turbopack development server, and reworks the caching defaults to be more predictable.

Turbopack Dev Server (Stable)

The Turbopack-powered dev server (next dev --turbo) is now stable. Vercel reports up to 76.7% faster local server startup and up to 96.3% faster Fast Refresh on large applications compared to the Webpack-based server.

next dev --turbo

Async Request APIs

APIs that previously accessed per-request data synchronously are now async. This is a breaking change but enables better streaming and partial prerendering:

// Next.js 15
import { cookies, headers } from "next/headers";

export default async function Page() {
    const cookieStore = await cookies();
    const token = cookieStore.get("token");
    // ...
}

Caching Changes

In Next.js 15, fetch requests, GET route handlers, and client-side router cache are no longer cached by default. You opt in to caching explicitly, making the behaviour more predictable and reducing hard-to-debug staleness issues.

React 19 Support

The App Router now fully supports React 19 stable features including the new useActionState, useFormStatus, and Server Components improvements introduced in React 19.