App and system caches: 4.1 GB median, largest single category
App and system caches represent the largest single category in aggregate, accounting for a median 4.1 GB on a first scan. The distribution across Mac types shows a clear pattern: browser caches (Safari, Chrome, Firefox) account for 1.2-1.8 GB on average Mac users; developer tool caches (npm global store, Homebrew downloads, Docker overlay layers) add 2-4 GB on developer machines. System caches — font glyph maps, icon databases, Spotlight index fragments — add 0.3-0.8 GB across all Mac types. The removal of app and system caches has the most immediate effect on disk pressure because these files are large and concentrated. They are also the fastest to re-accumulate: a Mac that has been cleaned returns to its previous cache volume within four to eight weeks of normal use, which is why a scheduled monthly scan recovers a consistent 2-4 GB each run.