Authy is being used by Auth0 to add 2-Factor Authentication (2FA) to their applications, making it easier for developers to implement this security feature. The process involves using the Authy TOTP API and the Auth0 Management API to register users with Authy and verify their one-time passcodes. With just a few API calls, developers can set up 2FA in no time. The guide also highlights the benefits of using Authy, including its robust and well-designed solution for both developers and users. Additionally, it explains how to integrate Authy with Auth0's authentication platform, making it easier for teams to protect user accounts.