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Duo MobileProton Authenticator
Free

The app is free. The Duo service behind it is a paid product for organisations.

 Free

Free and open source under the GPL, with no advertising. A Proton account is used for…

Android, iOS Windows, Linux, Android, iOS
  • Verified Push defeats the push-fatigue attacks that plague plain approvals
  • Also works as an ordinary TOTP authenticator for other accounts
  • End-to-end encrypted sync between devices, which most free authenticators lack
  • Apps for Android, iOS, Windows, Linux and macOS
  • Built around a Duo deployment that an organisation pays for
  • Closed source
  • Sync requires a Proton account
  • Keeping codes on the same desktop you log in from weakens second-factor separation
Downloadable app Downloadable app
Closed source Open source
License not stated License: GPL-3.0
Not stated if an account is needed No account needed
Not stated if it works offline Works offline

Checked September 22, 2026

Checked September 21, 2026

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