1. We never see your files
The scan runs on your computer. What it sends us is a catalogue: file names, paths, sizes, dates, types, and a fingerprint of each file's contents. Not the contents.
A fingerprint is a one-way hash. It lets us tell that two files are identical without holding either one, and it cannot be turned back into a file. There is no feature that uploads, stores or backs up your files, and no code path that reads a file's bytes to the network.
Honest caveat, because it matters: file names and folder paths can themselves be revealing. If that is a problem for a particular drive, scan it without linking the agent to an account — the local report works exactly the same.
2. Nothing is ever deleted
A cleanup does not delete. It moves duplicates into a folder called _SiftDrive_Quarantine on the same drive, keeping their original paths inside it. Your disk still holds every byte it held before; it is just arranged so you can look at what would go.
Emptying that folder is your own separate act, whenever you are satisfied. And if you are not: siftdrive undo puts everything back where it was.
3. An interrupted cleanup is still reversible
Before each file moves, the agent writes down what it is about to do and flushes that record to disk. So a cleanup interrupted by a crash, a power cut or an unplugged cable is still a cleanup that can be undone — the journal knows what had happened and what had not.
Each file is also re-checked immediately before it moves, and skipped if anything about it changed since the plan was made. And there are places a cleanup refuses to touch at all: inside application bundles and system directories, duplication is how software is built rather than waste, and reclaiming a few megabytes by breaking an installed program is not a trade anyone asked for.
4. We do not promise numbers we cannot verify
Duplicates are matched by comparing contents, not names. Hard links are counted as the single file they are — an early version counted them as separate copies and overstated one test drive's reclaimable space by a factor of forty.
On filesystems that support copy-on-write clones, including APFS on modern Macs, two identical files may already share the same storage, so removing one frees nothing — and no software can reliably tell after the fact. Where that applies the report says space is recoverable at most. Where it does not — most external drives, memory cards and USB sticks — the figure is exact.
Still: keep backups
Everything above is real and none of it replaces a backup. Storage fails, filesystems corrupt, and software has bugs, including ours. Do not run a cleanup on the only copy of something you cannot lose.
The rest
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