For GitHub, the second form of authentication is a code that's generated by an application on your mobile device or sent as a text message (SMS). After you enable 2FA, GitHub generates an authentication code any time someone attempts to sign into your GitHub account. The only way someone can sign into your account is if they know both your password and have access to the authentication code on your phone.

After you configure 2FA using a mobile app or via text message, you can add a FIDO U2F security key, and configure additional recovery methods in case you lose access to your two-factor authentication credentials. For more information on setting up 2FA, see "Configuring two-factor authentication" and "Configuring two-factor authentication recovery methods."

We strongly urge you to turn on 2FA for the safety of your account, not only on GitHub, but on other websites and apps that support it. You can use 2FA to access GitHub via:

• The GitHub website
• The GitHub API
• GitHub Desktop

For more information, see "Accessing GitHub using two-factor authentication."

Apple ID 的双重认证 - Apple 支持 https://support.apple.com/zh-cn/HT204915