Requiring more than just your password to access your account improves the security of your Apple ID and all personal information you store with Apple.
It protects your account by requiring a password and access to either a trusted device or verification code delivered via SMS or phone call.
Two-factor authentication is an extra layer of security for your Apple ID designed to ensure that you’re the only person who can access your account, even if someone knows your password. About two-factor authentication What is it?
This extra layer of security for your Apple ID helps ensure that you’re the only person who can access your account. Two-factor authentication or two-step verification is required for all users to sign in to App Store Connect. In some cases, you might be able to speed up account recovery or rest your password by simply verifying a 6-digit code sent to your primary email address.In an effort to keep your account more secure, two-factor authentication is required for developer program Account Holders to sign in to their Apple Developer account and Certificates, Identifiers & Profiles.
Inability to verify Apple ID due to phone loss, phone replacement, or other issues that limit access to your phone number means you won’t be able to use a lot of services or access your iCloud account.
This is often the case after an iOS update or when you lose your phone and try signing in to a new device. Apple ID verification issues including “cannot verify phone number Apple ID” can be very frustrating.