FreeFileSync Mirror vs Update on Windows: Which Is Safer?
Quick answer
Mirror aims to make a destination match its source, including deletions; Update leaves destination-only files in place. Neither replaces an independent versioned backup.
When Mirror is appropriate
Choose Mirror for a controlled replica when the source is authoritative and deletions are intentional. Review every planned removal in the comparison grid.
When Update is appropriate
Choose Update for a one-way transfer where destination-only files should remain. Changed destination files can still be overwritten, so check the action arrows.
Safety test
Create source-only, destination-only and modified test files. Compare both variants and note which operations change before running on real data.
Recovery decision
If either folder contains irreplaceable work, preserve a separate recovery copy and consider versioning. Do not use an untested mode on the only copy.
Before you run the job
Use disposable test folders for the first pass. Keep an independent copy of important files, confirm drive identities, and run Compare before Synchronize. A preview is not a substitute for checking the actual destination afterwards.
Related FreeFileSync Windows guides
Source and review notes
This guide explains a focused Windows workflow. Consult the current FreeFileSync developer manual for precise behavior and edition-specific options. Review each planned file operation and test with non-critical files before relying on a procedure.