What’s New in Next.js 15.5: Turbopack Beta, Stable Middleware, and TypeScript Upgrades

The newest Next.js release laid some groundwork for version 16. So, what’s new in Next.js 15.5?

First of all, next build –turbopack officially entered beta! Vercel websites like vercel.com, v0.app, and nextjs.org are all powered by Turbopack now, which has served 1.2 billion requests since its release.

According to Vercel, all types of sites deployed on Turbopack saw big speed increases, ranging from x2 to even x5 faster performance.

After extensive testing since its introduction in version 15.2, Node.js middleware is finally stable. It can now handle more complex use cases with the same great DevEx.

While it likely won’t be the default in Next.js 16, the Vercel team is considering changing that in version 17, based on community feedback.

TypeScript saw some improvements as well:

• Typed Routes, available behind the typedRoutes flag, are now stable.
• Route export validation works on Turbopack using TypeScript’s satisfies operator.
• Next.js now generates globally available PageProps, LayoutProps, and RouteContext types automatically.
• next typegen command was added for manual type generation without needing to run next dev or next build.

next lint wil be deprecated in version 16, and is already showing warnings. When creating a new project in Next.js, you can choose ESLint (comprehensive rules), Biome (fast with fewer rules), or no linter options.

Additional depreciation warnings for version 16 include:

• legacyBehavior for next/link
• AMP Support
• next/image Quality Settings
• next/image Local Patterns

To learn more, read the full release post.

Want to learn more about Next.js? Download the CTO’s Ultimate Guide to Next.js

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