Next.js and Turbopack

Next.js 16+ uses Turbopack by default for local development: an incremental bundler written in Rust that significantly speeds up dev startup and hot updates.

When to Use

• Turbopack (default dev): Use for day-to-day development. Faster cold start and HMR, especially in large apps.
• Webpack (legacy dev): Use only if you hit a Turbopack bug or rely on a webpack-only plugin. Disable with --webpack.
• Production: Production build may use Turbopack or webpack depending on Next.js version.

Use when: developing or debugging Next.js 16+ apps, diagnosing slow dev startup or HMR, or optimizing production bundles.

How It Works

• Turbopack: Incremental bundler for Next.js dev. Uses file-system caching so restarts are much faster (e.g. 5–14x on large projects).
• Default in dev: From Next.js 16, next dev runs with Turbopack unless disabled.
• File-system caching: Restarts reuse previous work; cache is typically under .next.

Commands

next dev          # Development with Turbopack (default)
next build        # Production build
next start        # Start production server

Best Practices

• Stay on a recent Next.js 16.x for stable Turbopack and caching behavior
• If dev is slow, ensure you're on Turbopack (default) and cache isn't being cleared
• For production bundle size issues, use official Next.js bundle analysis tooling