Bitwarden Authenticator is a standalone app that is available for everyone, even non-Bitwarden customers.
In its current release, Bitwarden Authenticator generates time-based one-time passwords (TOTP) for users who want to add an extra layer of 2FA security to their logins.
There is a comprehensive roadmap planned with additional functionality.
Available for iOS and Android
How does 2FA work without an internet connection?
it’s basically just a shared random number generator on a timer (it’s slightly smarter than that but that’s the gist), so as long as you know the start time, the current time and the starting point for the RNG, both parties can get the same result without having to ever communicate