# Two-factor authentication

2FA requires two independent proofs to log in: something you know (password) plus something you have (a phone receiving a code, an authenticator app or a hardware key).

## What is Two-factor authentication?

2FA requires two independent proofs to log in: something you know (password) plus something you have (a phone receiving a code, an authenticator app or a hardware key).

## SMS as a second factor

SMS 2FA sends a code to the phone number on the account. It is convenient but exposed to SIM swap and phishing, so services increasingly prefer authenticator apps or passkeys.

## Using a rented number for 2FA

If an account's second factor is SMS, the number must still be yours at the next login. Rent the number rather than buying a one-time activation, or switch the account to an authenticator app after sign-up.

Source: https://smsnitro.com/glossary/2fa