What is the difference between OTP and 2FA?

Short answerAn OTP is a single-use code. 2FA is the security design that asks for a second proof of identity in addition to a password. An OTP is one way to deliver that second factor — the most common one — but 2FA can equally use an authenticator app, a hardware key or biometrics.

What counts as a factor?

Two-factor authentication means two different categories from that list. A password plus a security question is not 2FA, because both are things you know.

• Something you know — a password or a PIN.
• Something you have — a phone receiving an OTP, an authenticator app, a hardware key.
• Something you are — a fingerprint or a face scan.

Is an SMS OTP secure enough?

It is far better than a password alone, and it is the only second factor that works for every customer without installing anything — which is why it remains the default for consumer signup and checkout.

Its known weaknesses are SIM-swap fraud and interception. Where the stakes are high — moving money, changing account recovery details — an authenticator app or a hardware key is stronger. For most consumer flows the realistic alternative to an SMS OTP is no second factor at all, which is worse.

What makes an OTP implementation good?

• Short expiry. Two minutes is plenty; an hour is an invitation.
• Single use. The code dies the moment it is used or a new one is issued.
• Rate limiting on both requests and verification attempts.
• Never in the message preview alone — and never reused across purposes.
• Fast delivery. Under three seconds. Every extra second of waiting costs you completed signups.