Allocated Size vs Apparent Size on macOS

Apparent size: the file's logical length

Apparent size is how many bytes the file presents to software. A sparse virtual disk may have room for hundreds of gigabytes logically even when many of those regions have never been written.

Allocated size: the blocks currently occupied

Allocated size measures filesystem blocks assigned to the file. It is usually the more useful default when the question is why the disk is physically full or how much capacity a deletion may return.

Cases that complicate both totals

• Sparse files: logical length can be far larger than allocated blocks
• Hardlinks: several paths can refer to one physical file and must be deduplicated
• APFS clones: files may share extents that public APIs cannot cheaply attribute perfectly
• Compression and block rounding: physical allocation can differ from byte length
• Snapshots and purgeable space: consumed capacity may not belong to an ordinary visible file

How Storage Map reports size

Storage Map defaults to allocated size, offers apparent size as an alternate view, and deduplicates hardlinks by filesystem identity. It also explains exclusions and APFS layout instead of forcing every storage concept into one misleading total.

No analyzer can promise that summing every visible file will exactly equal Finder's capacity number. The tools measure related but not identical layers of macOS storage.