Last Google replaced SMS based verification with device-based Prompts. However, that was not the case for iOS, and they had to rely on Google app for two-factor authentication when logging in. To save them from the trouble, Google is now rolling out the 2-Step verification prompts for iOS Gmail app.
Since SMS security codes are vulnerable to spoofing, Google implemented the “Google Prompt,” which upon signing in to a Google app or service, your phone will receive a notification asking you to confirm your login. Additionally, Google provides more information regarding the login by disclosing browser, and the operating system is being used to sign-in, the location, IP address, and the exact time.
Users were earlier instructed to install Google app, which offers full Search and Feed experience. A notification will be displayed asking users to open the app where they will be greeted with a full-screen Prompt. If both Gmail and Google app is installed, the prompt will default to Gmail. This security functionality will be rolling out in the coming weeks.