OTP, 2FA and MFA Explained in Plain Words
OTP is a one-time code, 2FA means logging in with two different factors, and MFA means using two or more. The terms overlap, which is why they get confused.
OTP. One-time password
A code that works once and expires quickly. It can arrive by SMS, email, or be generated by an authenticator app.
2FA. Two-factor authentication
Logging in with two different kinds of proof. The usual combination is something you know, your password, plus something you have, your phone.
MFA. Multi-factor authentication
The general term for using two or more factors. 2FA is simply MFA with two.
The three kinds of factors
- Something you know. Password, PIN.
- Something you have. Phone, security key.
- Something you are. Fingerprint, face.
Which is strongest
- Passkeys and hardware security keys. Resistant to phishing.
- Authenticator app codes. Not tied to your phone number.
- SMS codes. Better than nothing, but tied to your number.
Where SMS codes still fit
Many sites use SMS codes to confirm a phone number at sign up. For one-off sign ups where you'd rather not share your personal number, telly.cat rents numbers that receive the code for you.
FAQ
Is OTP the same as 2FA?
No. An OTP is a one-time code. 2FA is the practice of using two different factors to log in, and an OTP is often one of those factors.
Is MFA better than 2FA?
2FA is a type of MFA with exactly two factors. What matters most is how strong each factor is, not just how many there are.