FAQ

FAQ

About the numbers

Why do SDTally's numbers differ from Finder? Finder shows apparent size. SDTally counts allocated blocks: a sparse VM disk that declares 100 GB may occupy 2.5 GB, a cloud-only placeholder occupies 0, and blocks shared by APFS clones are counted once. See Understanding System Data.

Why do they differ from System Settings? They measure different things. Settings classifies files into categories and puts the remainder in System Data; it also treats purgeable space as available. SDTally shows Apple's numbers next to its own (the "System Settings screen (reproduced)" block) and names the source of every number. sdtally --verify compares used space, swap and snapshots with Apple's own commands, side by side.

GB or GiB? GB (10^9 bytes) by default, like System Settings. Use --binary in the CLI for GiB (2^30), like du and df. The difference is about 7 percent.

What is "unexplained" or "Blocked by macOS"? Used space minus everything SDTally measured. It is mostly what macOS would not let SDTally see. Run a full measurement as root with Full Disk Access to make it small. It never goes negative; if measured parts overlap, it is reported as not measured with the overlap amount.

The System Data line says "no record". The number only exists in the Storage pane's log, which keeps it for less than about 21 hours. Open System Settings > General > Storage, wait for it to load, and run again. The app can open System Settings out of sight to refresh it; see Settings > Automatic Refresh.

What is "freed if deleted"? The private bytes of a row: what deleting it would actually return, excluding blocks shared with clones or other files.

Space that does not come back

I deleted a big folder and free space barely changed. The "Why space may not come back" block lists the measured causes of 1 GB or more:

• a local snapshot still holds the blocks,
• an app still has a deleted file open (quit it or restart),
• the file was an APFS clone sharing blocks with another file,
• it was a cloud-only placeholder and never took space,
• it is in the Trash, which has to be emptied,
• the space is purgeable, so Settings already showed it as available.

Should I delete local snapshots? macOS removes Time Machine local snapshots on its own when space runs low. If you decide to remove them, use Apple's tmutil, never anything else. SDTally only lists them (tmutil listlocalsnapshots /).

The app

The app will not open: "cannot be opened because the developer cannot be verified". SDTally is not notarized. Open System Settings > Privacy & Security and click Open Anyway once.

Why is it not notarized? Notarization requires a paid Apple Developer membership. Release builds are signed with an Apple Development identity. You can build it yourself; see Building from source.

Does it check for updates? No. It never uses the network. Settings > See New Versions opens the Releases page in your browser.

What is the difference between Automatic and Manual? Automatic is live, per folder, and needs no password. Manual shows the latest Full Measurement, which is per file, lists the largest files, and opens protected folders as root. See Automatic vs Full measurement.

Do I need Passwordless Root? No. It only saves typing the password for each full measurement and enables Automatic with root. Read Passwordless Root helper first.

Passwordless Root says "Waiting for Approval in Login Items". Click Open Login Items and allow SDTally there.

Passwordless Root will not install on my own build. Your build is probably signed ad hoc. app/montar.sh needs an Apple Development identity in your keychain (a free Personal Team certificate works). Without one, the helper cannot register.

Full Disk Access is lost every time I rebuild. Same cause: ad hoc signing. Sign with an Apple Development identity.

Where does the app keep its data? ~/Library/Application Support/SDTally. File > Show Saved Measurements in Finder opens it. Nothing leaves your Mac.

Can I change the language? Yes. Settings > Appearance > Language, for SDTally only. It applies after reopening the app. The CLI's text output is in Portuguese or English (--lang).

Scope

Does it work on Intel Macs, or on macOS 14 or earlier? No. Apple Silicon and macOS 15 or later.

Can it measure an external disk? No. It measures the boot Data volume. Paths on other volumes are refused, and external Trash folders are not scanned.

Will it clean my Mac? No. It explains what takes space and recommends a next step. You decide and act, in Finder, the owning app or System Settings.

Can an AI agent use it? Yes, read-only: sdtally --mcp, --quick --json, --last --json. See JSON output. The agent never gets root and never runs a recommendation by itself.

Is it safe to share a measurement? Use Export JSON or Export PDF with "Replace Personal Names" on, or sdtally --redact names. Review before posting. See Privacy and safety.