This is primarily a one-to-one video calling app, although users can also make audio-only calls to friends. Google Duo operates across Android and iOS systems and can give the user a preview image of who their caller is before the user answers.
Why is it a risk?
Google Duo users must verify their account with a contact telephone number, making it harder for children to contact or be contacted by people they don’t know. The "knock-knock" service also allows users to see a preview message of who is calling before they answer.