Finder often shows the length of a file. dux shows the space it occupies on disk and what removing it really frees.
- On disk is the space a file really uses. Sparse and compressed files use less than their length.
- Can be freed is what moving the item to the Trash would free once the Trash is emptied. Hard links and APFS clones lower this number, because another name or copy still holds the data.
- Logical size is the length of the file, the number Finder shows as size.
- Online only cloud files use no space on this Mac.
Folders dux could not read are counted as unknown, not zero. See Full Disk Access.