Usage

Situation	What happens
New shopper	Clicks Continue with Google, approves, and comes back signed in with a new account (if registration is allowed)
Google confirms the e-mail of an existing customer	The Google account is connected and the customer is signed in
The address is not confirmed, or Existing e-mail = ask password	The customer enters the account password once; the account is connected
No e-mail from Google	A short Complete your sign-up step asks for the e-mail
Customer profile	Connected accounts lists the Google account with Disconnect
Social Login Pro installed and active	This add-on shows a notice in the admin and no button; Social Login Pro shows the buttons

Statistics: Customers > Google sign-in > Statistics.