Twilio is a cool service for programmatic communication (chat, voice, video, and email.) It also provides a phone verification API that can help you to validate leads coming through your landing pages.
The process is simple: the user provides a phone number, your back-end system sends a request to the Twilio Verify API; Twilio will send a code to the user’s phone, the user enters the code, and you can verify it against Twilio’s API.
For this 2-Factor validation, Twilio uses Authy. It creates an OTP (one-time-password), which means the same API endpoint can be used for passwordless logins.
Phone verification is another form of two-factor authentication. You can use it to validate leads or allow users to restricted websites/apps without having them create an account.