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Proton Authenticator vs Flauth: catalog facts
Proton Authenticator	Flauth
Free Free and open source under the GPL, with no advertising. A Proton account is used for…	Free Free and open source under the MIT licence.
Windows, Linux, Android, iOS	Windows, macOS, Linux, Android, Command line
End-to-end encrypted sync between devices, which most free authenticators lack Apps for Android, iOS, Windows, Linux and macOS	Same authenticator on Android and all three desktop systems Command-line tool for reading codes in a terminal
Sync requires a Proton account Keeping codes on the same desktop you log in from weakens second-factor separation	Small, young project with a single main developer No iOS app listed among the downloads
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License: MIT
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked October 2, 2026

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