Pew Research Center with stats & numbers from the US market on generation Z. 95% of US teens have a smartphone, and 45% say they are online "almost constantly". That's coming from 24% in 2015 and is a dramatic increase. In platforms used overall YouTube leads (72%), followed by Instagram and Snapchat, while "most used platform" is led by Snapchat. Nothing that you wouldn't know if you have an n=2 group of teens in your personal environment, but it helps to see these impressions verified on scale by research.