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bup vs Kopia: catalog facts
bup	Kopia
Free Free and open source.	Free Free and open source, with no paid edition.
macOS, Linux, Command line	Windows, macOS, Linux, Command line
Global deduplication across and within files Fast incremental saves	A desktop app and a command line tool that share the same repository format End-to-end encryption with keys you control, plus compression and deduplication
Command line only Development discussion happens on a mailing list rather than GitHub issues	Backs up the files and folders you choose; it is not a whole-disk imaging tool Still pre-1.0, so repository format changes between versions are possible
Downloadable app	Downloadable app
Open source	Open source
License: LGPL-2.1	License: Apache-2.0
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 20, 2026

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