Reviewed July 28, 2026 · DiskStory
What is taking up space on my Mac?
Compare physical usage, observed files, permission gaps, and unexplained space without turning the remainder into a cleanup promise.
Direct answer
Start with three separate numbers: the file system’s physical used space, the allocated size of files the scan could observe, and the remainder that cannot yet be attributed. The remainder can include APFS snapshots, file-system overhead, auxiliary volumes, clones, and unreadable locations.
Use allocated size for physical impact
Logical size can mislead for sparse files, compressed data, and clones. DiskStory keeps allocated size as the primary storage measure while retaining the scope and path behind the number.
Treat unreadable paths as evidence gaps
A permission error is not a zero-byte folder. Full Disk Access can remove some TCC restrictions, but it cannot bypass every Unix permission, SIP rule, or private Data Vault.
Do not call the remainder reclaimable
The difference between physical usage and observed files is an accounting remainder. It should not generate a removal recommendation until a specific, supported rule identifies an exact path.