Are ALL files on _next/static served with immutable cache?

[benjavicente]

Summary

The new documentation about caching in production (Next.js 15 app dir) has:

Next.js sets the Cache-Control header of public, max-age=31536000, immutable to truly immutable assets. It cannot be overridden. These immutable files contain a SHA-hash in the file name, so they can be safely cached indefinitely. For example, Static Image Imports. You can configure the TTL for images.

It isn't clear where are the immutable assets. In the old documentation of caching in production (Next.js 13 pages dir), it mentions that immutable assets are served from /_next/static, but not that all of the contents of the /_next/static are inmutable:

Caching improves response times and reduces the number of requests to external services. Next.js automatically adds caching headers to immutable assets served from /_next/static including JavaScript, CSS, static images, and other media.

Cache-Control: public, max-age=31536000, immutable

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In all Next.js deployments (pages, app dir), it is ok to cache ALL contents of the /_next/static path with immutable cache, or are there any files that could change?

It isn't clear if all /_next/static/* is guaranteed to be immutable 🤔

Additional information

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Example

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