Two-step verification is a security feature for Apple ID that’s designed to prevent anyone else from accessing or using your account, even if they know your password.
It requires you to verify your identity using one of your devices or another approved method before you can:
Once two-step verification was set, when you sign in to manage your Apple ID, sign in to iCloud, or make an iTunes, iBooks, or App Store purchase from a new device, you need to verify your identity by entering both your password and a 4-digit verification code. Without both your password and the verification code, access to your account is denied.
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