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OTPClientProton Authenticator
Free

Free and open source under the GPL-3.0 license.

 Free

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

Linux, Command line Windows, Linux, Android, iOS
  • Multiple encrypted token databases
  • Supports TOTP, HOTP and Steam Guard codes
  • End-to-end encrypted sync between devices, which most free authenticators lack
  • Apps for Android, iOS, Windows, Linux and macOS
  • Desktop Linux only, no mobile app
  • Handles one-time codes only, not passwords
  • Sync requires a Proton account
  • Keeping codes on the same desktop you log in from weakens second-factor separation
Downloadable app Downloadable app
Open source Open source
License: GPL-3.0 License: GPL-3.0
No account needed No account needed
Not stated if it works offline Works offline

Checked September 24, 2026

Checked September 21, 2026

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