Two-factor authentication
Two-factor authentication is an extra layer of security for your Apple Account designed to ensure that you’re the only person who can access your account, even if someone knows your password.
You can turn on two-factor authentication and manage your trusted devices and phone numbers by signing in to your Apple Account website. If you create a new Apple Account on a device with iOS 13.4, iPadOS 13.4, macOS 10.15.4, or later, your account automatically uses two-factor authentication.
Enroll in two-factor authentication
If your account meets all the requirements for two-factor authentication, you are prompted to turn it on when you first use your device.
Important: If you’re using two-step verification, you must turn it off before you can turn on two-factor authentication. To do so, sign in to the Apple Account website. In the Security section, tap Edit, then tap Turn Off Two-Step Verification. You’re asked to create new security questions and verify your date of birth. You should receive an email confirming that two-step verification for your Apple Account is turned off.
Use two-factor authentication
After you’re enrolled, when you enter your Apple Account password for the first time on a new device, you’re asked to verify your identity with a six-digit verification code. This code is displayed automatically on your other devices or sent to a phone number you trust. Just enter the code to sign in and access your information on your new device.
You won’t be asked for a verification code again on that device unless you sign out of your device completely, erase your device, or need to change your password for security reasons.
As extra protection for your Apple Account against phishing attacks, you can use a physical security key instead of a verification code. See the Apple Support article About security keys for Apple Account.
See the Apple Support article Two-factor authentication for Apple Account.