Why Is Gmail Asking for My Phone Number for Verification?

When you sign up for a Gmail account, Google will ask for personal information such as your name, birthday and gender. All of these fields are human attributes, but don't necessarily prove that the device signing up for an account has a human behind it. Robots are getting better at solving CAPTCHA, the image test usually used to separated humans from computers. Robots cannot, however, check a phone for a verification code and plug the code into Gmail for authentication. When Google asks for your phone number during account creation, it is to implement a new and more effective form of differentiating humans from robots. This keeps down the number of accounts created through mass automation. As an added bonus, you don't need to submit a CAPTCHA if you verify by phone.

Google limits the number of email addresses someone can create with one phone number. When you hit the maximum number of accounts, the service sends you a message saying that the phone number you entered has created the maximum number of accounts allowed. That doesn't mean that you can't create any more accounts, just that you'll have to use another phone number to do so. This measure limits spam by making it more difficult for people to create lots of fake accounts in a short time.

By default, every time you sign in to Gmail, Google performs a risk analysis to determine whether the login is coming from you. If it determines that it may not be you, Google asks for either the phone number you gave when signing up for the account or an answer to a security question. You can easily these questions while hackers cannot.

You can take login security one step further by signing up for Google's "2-Step Verification." With this option turned on, when you sign in to your account Google asks for your password and then sends a unique code to the phone number you provided at account creation. By entering the code into the second verification step, you can access your account. You can choose to only do this verification once per device. In this way, Google adds an extra layer of protection to your account.

If someone gets into your account and changes your password, you will find yourself locked out. To recover your account, Google asks you provide your username and choose a method of recovery. One of the safest methods is by using your phone number. Google sends a password reset code to your phone, which you can then use to regain access to your account.