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Proton Authenticator vs Yubico Authenticator: catalog facts
Proton Authenticator	Yubico Authenticator
Free Free and open source under the GPL, with no advertising. A Proton account is used for…	Free The app is free; it requires a YubiKey, which is bought separately.
Windows, Linux, Android, iOS	Windows, macOS, Linux, Android, iOS
End-to-end encrypted sync between devices, which most free authenticators lack Apps for Android, iOS, Windows, Linux and macOS	Secrets stay on the hardware key rather than the device Same codes available on any machine where the key is plugged in
Sync requires a Proton account Keeping codes on the same desktop you log in from weakens second-factor separation	Requires a YubiKey Losing the key loses access to the stored codes unless you have a backup
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-3.0	License not stated
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 21, 2026	Official website Full listing and sources Checked September 24, 2026

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