Aegis Authenticator

The authenticator app is the weakest link in many people's security setup. Google Authenticator went years without encrypted backups, making a phone change a disaster; Authy ties you to a phone number and keeps secrets on the vendor's servers, and when it discontinued its desktop app in 2024 a lot of people were forced to migrate anyway.

Aegis takes the opposite position: the secrets never leave this phone. 12,899 stars, GPL-3.0.

Key design decisions:

• The whole database is encrypted. Opening the app requires a master password or fingerprint, so even an unlocked phone does not hand over your code list. Google Authenticator still handles this poorly.
• It requests no network permission. You can verify this in Android's own settings — with no network access, uploading secrets is impossible, which beats any privacy promise on a website.
• Exports are under your control. Encrypted backup files can be stored wherever you trust: locally, in your own cloud, inside an encrypted volume. Restoring on a new phone depends on no vendor at all.
• Migration-friendly. It imports from Google Authenticator, Authy, FreeOTP and andOTP, and it exports cleanly when you leave. No lock-in in either direction.

Two practical warnings:

• Android only. iOS users should look at Ente Auth, which is also open source, or the system's built-in password app.
• Backups are your responsibility. The flip side of no cloud custody is that a lost phone with no backup means those codes are genuinely gone. Export an encrypted backup as the very first thing you do, and store each site's recovery codes separately. Skipping this step is expensive.

If you want two-factor authentication that requires trusting no company, this is the standard answer on Android.