2FA (two-factor authentication)
Definition
Signing in with two different proofs, typically a password plus a code, app prompt, passkey or security key.
2FA (two-factor authentication), explained
Two-factor authentication, or 2FA, requires two independent proofs when you sign in: usually something you know, like a password, and something you have, like your phone or a security key. Common second factors are SMS codes, authenticator app codes, push prompts, passkeys and hardware keys. Any of them is far better than a password alone. SMS is the easiest but weakest, because it depends on your phone number staying in your control. For important accounts, prefer an authenticator app, passkey or security key, and save the backup codes. Never use a temporary number as your 2FA method on an account you keep.
Related terms
Authenticator app
An app that generates time-based login codes on your device, with nothing sent over the phone network.
Passkey
A phishing-resistant sign-in credential stored on your device and unlocked with your fingerprint, face or PIN.
SIM swap
An attack where someone gets your carrier to move your number to their SIM so they receive your calls and codes.
Where you'll meet this term
What Is SMS Verification? How OTP Codes Work and Safer Alternatives
What SMS verification and one-time passcodes are, why sites use them, how codes are delivered, and how SMS 2FA compares to authenticator apps and passkeys.
Read the guide →Safety & privacyTwo-Factor Authentication Explained: SMS, Authenticator Apps, Passkeys and Security Keys
2FA explained: SMS codes, authenticator apps, passkeys and hardware security keys compared, with clear recommendations for your accounts.
Read the guide →Safety & privacySIM Swap Protection: What SIM Swapping Is and How to Stop It
What SIM swapping is, warning signs, and how to protect your accounts with a carrier PIN, port-out lock and 2FA that doesn't rely on SMS.
Read the guide →Safety & privacyWhy Websites Ask for Your Phone Number, and When It's Worth Giving
Why sites and apps ask for your phone number: bot prevention, 2FA, recovery, marketing and data. When it's worth giving and when to hold back.
Read the guide →SMS codes vs Authenticator appSMS codes vs authenticator apps for 2FA
Authenticator apps resist SIM swaps and interception better than SMS codes. SMS 2FA is easier to recover. How each works and when to use which.
See the comparison →Temporary number vs Your own numberThe best phone number for gaming accounts
Steam, Epic, Roblox, Blizzard and more: when a temporary number is fine for a gaming account and when you need a number you'll keep for recovery.
See the comparison →