All APFS volumes in a single partition/container share its free space. How can that be measured? How much could be purged, and how do special file types affect it?
purge
Where are all those purgeable files? Two updated utilities to help you find them: Precize and Sparsity, which will crawl folders checking which files are purgeable, sparse or clones.
Performed by CacheDelete, it first looks at a wide range of macOS caches, and only at the end purges snapshots, to free up space when it runs short.
Although my Mac has 6 GB of memory, I have had to use the purge command with depressing frequency since OS X 10.6, before quitting anything, particularly Safari.
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