Understanding the _next Directory in Next.js

The _next directory is a reserved path used by the Next.js framework to serve internal assets, build manifests, and pre-rendered data. When a React application is built using the next build command, the resulting production files are typically stored in a hidden .next folder. However, when these assets are served to the client, they are exposed via the /_next/ URL prefix.

This directory plays a critical role in Client-Side Rendering and Hydration. It contains various sub-directories, most notably /_next/static/, which holds JavaScript chunks, CSS files, and images optimized by the Next.js Image Component. For applications utilizing Static Site Generation or Server-Side Rendering, the /_next/data/ path is used to fetch JSON files containing the props required for page transitions without a full browser reload.

Security and infrastructure configurations, such as those found on Vercel or AWS, often need to account for this path to ensure that Caching headers are correctly applied to immutable assets. According to the Next.js Documentation, the default distribution directory can be renamed, but the public-facing /_next/ prefix remains a standard for the framework's internal routing mechanisms managed by Webpack or Turbopack.

• Routing
• Middleware
• Incremental Static Regeneration
• Edge Runtime