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FreeFileSync vs Unison: catalog facts
FreeFileSync	Unison
Free Free to download and use; the project runs on advertising and donations. A paid Donation…	Free The open-source application is available without a license fee.
Windows, macOS, Linux	Windows, macOS, Linux
Transfers only the differences between source and target instead of copying everything Saved jobs run unattended in batch mode, suitable for scheduled backups	Handles updates made independently on both replicas
The installer and the website carry advertising, and the download page pushes donations hard Some conveniences, including parallel file copying, are reserved for the paid Donation Edition	Conflicting edits may require a decision before synchronization.
Downloadable app	Downloadable app
Open source	Open source
License not stated	License: GPL-3.0
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 20, 2026	Official website Full listing and sources Checked September 22, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.