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Zero-TOTPProton Authenticator
Free

Free and open source under the GPL-3.0.

 Free

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

Web, Self-hosted Windows, Linux, Android, iOS
  • Zero-knowledge encryption of stored TOTP secrets
  • Use the hosted service or self-host it
  • End-to-end encrypted sync between devices, which most free authenticators lack
  • Apps for Android, iOS, Windows, Linux and macOS
  • iOS app still in development and CLI only planned
  • Small project with a limited contributor base
  • Sync requires a Proton account
  • Keeping codes on the same desktop you log in from weakens second-factor separation
Web application, Self-hosted Downloadable app
Open source Open source
License: GPL-3.0 License: GPL-3.0
Account needed No account needed
Not stated if it works offline Works offline

Checked October 2, 2026

Checked September 21, 2026

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