Authenticator is described as 'generates two-factor authentication (2FA) codes in your browser. Use it to add an extra layer of security to your online accounts' and is an app in the Web Browsers category. There are more than 25 alternatives to Authenticator for a variety of platforms, including iPhone, Android, iPad, Android Tablet and Windows Phone. The best alternative is Authy, which is free. Other great apps like Authenticator are andOTP (Free, Open Source), Aegis Authenticator (Free, Open Source), FreeOTP (Free, Open Source) and Google Authenticator (Free).
FreeOTP is a two-factor authentication application for systems utilizing one-time password protocols with support for Android (3.0 or later) and iOS (7 or later). Tokens can be added easily by scanning a QR-code or by manually entering in the token configuration.
Sign in is easy, convenient, and secure when you use Microsoft Authenticator. Use your phone, not your password, to log into your Microsoft account. You simply have to enter your username, then approve the notification sent to your phone.
LastPass Authenticator is a two-factor authentication app for your LastPass account and other supported apps. LastPass Authenticator offers simple, secure authentication to your accounts by generating passcodes for login or receiving push notifications for one-tap approval.
The app for calculating one-time-passwords on iPhone and iPad. OTP Auth can be used with any service that uses one time passwords. This includes services like Dropbox and GMail with two-step-verfification enabled. OTP Auth is QR code enabled.
As the name should already tell you, Authenticator is a desktop 2FA code generator for Linux desktops, like Ubuntu. Using it you can generate 2FA tokens for over 500 well-known providers, including Github, Gitlab, Twitter, Facebook, Google, Dropbox, and Twitch.