The Authy API is being phased out in favor of the Verify API, which offers improved features and a better developer experience. The Verify API provides various helper libraries for popular programming languages and supports multiple authentication methods, including SMS, voice, and email one-time passcodes. To onboard users with Authy two-factor authentication (2FA), developers need to register them via a REST API call, store their unique AuthyID in the database, and enforce 2FA by sending a second factor request. The AuthyID serves as a disassociated user identifier, allowing for phone number changes without affecting support calls. Developers can design their own user experience with various authentication approaches, including SoftToken, OneCode, and OneTouch, which offer different levels of security and convenience.