The Best Open-Source 2FA App

This list covers open-source two‑factor authentication apps for people who want to generate and manage one‑time passcodes on mobile or desktop without relying on closed ecosystems. It focuses on TOTP/HOTP apps with transparent code, cross‑platform options for Android, iOS, and desktop, offline capability or optional encrypted sync, current or recently maintained projects circa 2023–2025, and global availability; it excludes proprietary-only authenticators, hardware-only tokens, and password managers whose 2FA is incidental rather than primary.