FreeOTP

FreeOTP produces the one-time codes asked for as a second step when logging in to a service. Adding an account is done by scanning the QR code the service displays, or by typing the setup details by hand when no code is shown.

It handles both of the usual schemes: TOTP, where the code changes every thirty seconds, and HOTP, where it advances each time one is used. The list shows accounts by name with the current code, and tokens can be renamed and given a colour or icon so that a long list stays readable.

It is deliberately small in scope — no account to create, no server to sign in to, nothing sent anywhere. That also means the tokens live only on the device, so setting up a replacement phone means enrolling the accounts again.