SMS authentication—also known as SMS-based two-factor authentication (2FA) and SMS one-time password (OTP)—allows users to verify their identities with a code that is sent to them via text message. A form of two-factor authentication, it often acts as a second verifier for users to gain access to a network, system, or application, and is a good first step toward better security. However, it should be noted that SMS authentication is widely considered to be a weak form of verification. We’ll dig into the reasons why, but let’s first get an understanding of how SMS authentication works and the pros and cons of using it. How does SMS authentication work? This form of authentication is actually quite simple. After signing in, the user receives a text message with an SMS authentication code. All they need to do is enter that code on the app or website in question to gain.