Answer the deletion question first
The most important difference is not the label: it is whether files found only in the target should remain or be removed.
FreeFileSync search bridge
FreeFileSync Mirror vs Update: mirror removes extras; update keeps them
The practical difference is simple: Update copies new and changed source files while preserving files that exist only in the target. Mirror is for a deliberate replica, so target-only files can be removed after review. Compare first, then choose the outcome you actually want.
Available now on macOS. Windows and Linux are planned. Your files stay under your control.
Update keeps target-only files; Mirror can remove them after review.
Use Update for backups and archives that may legitimately contain extras.
Use Mirror only when the target should be an intentional replica of the source.
A deliberate workflow
A clear path from review to action
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Decide whether target-only files should stay
That is the mode decision. If target-only files are old exports, archive material, or anything you might still need, do not treat them as noise—use the preview to review them first.
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Choose Update for a conservative backup-style result
Use Update when the target should receive missing source files and changed versions but may legitimately contain extra files of its own. This is the safer default for a backup or archive.
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Choose Mirror only for an intentional replica
Use Mirror when the target is meant to match the source exactly. It can remove target-only files after copy/update succeeds, so it needs a careful preview and explicit confirmation.
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Verify the preview before you run either mode
Check new files, changed files, unchanged files, and target-only files. If the preview does not match your mental model of the two folders, stop and correct the folder pair or exclusions first.
Reduce sync mistakes
A visible preview makes it easier to spot an archive, export, or older file that should not disappear from the target.
Choose from the intended outcome
The right mode is the one whose result you can explain clearly before files move—not the one that sounds more thorough.
Product walkthrough
Watch a preview-first sync walkthrough
This walkthrough shows the review step that matters before choosing copy/update or mirror: understand changed files, target-only files, and unchanged files before you commit.
Common questions
Before you start
Does FreeFileSync Mirror delete files?
Mirror can remove files that exist only in the target because its goal is to make the target match the source. Review target-only files before confirming a mirror run.
Does FreeFileSync Update delete target-only files?
No. Update adds missing source files and refreshes changed ones while leaving target-only files in place.
When should I use Mirror instead of Update?
Use Mirror only when the target should become an exact replica of the source and you have already reviewed the target-only files carefully.
See the files first. Decide what happens next.
FileLever is available now on macOS, with Windows and Linux planned.