CACHEDIR

CACHEDIR is a general term used in computing to refer to a directory that stores data produced by software to speed up subsequent operations. Cache directories are expected to be writable, may contain nonessential data, and are typically regenerable when needed. The concept is widely used across build systems, package managers, and applications that cache downloaded or computed results.

Many projects follow a convention of placing a file named CACHEDIR.TAG in the root of a cache directory. This marker file is a small plain-text signal that the directory is a cache and not part of the permanent data. The contents usually consist of a short line beginning with the word Signature; the exact text is conventional rather than mandated. Tools and scripts that recognize this marker can treat the directory specially—often skipping it during backups, version-control operations, or archive creation.

Cache directories may reside in user spaces such as ~/.cache on Unix-like systems, or in system-wide locations such as /var/cache, or inside build directories. The directory is typically managed by the software that created it, and its contents can usually be discarded and rebuilt without affecting core data.

Best practices include placing CACHEDIR.TAG in caches that store generated or downloaded artifacts, avoiding storage of sensitive data in caches, and documenting what the cache holds. Implementing clear cache invalidation and refresh strategies helps ensure that caches remain effective without compromising data integrity or security.