It's going to be every website. There will be no place they will stop. You think a forum like this one where it's conceivably possible someone in a bad category could interact with someone under the age of 16, however unlikely, won't be regulated?
"But sir! The largest websites on the internet implement Government ID Age Check. Just federate with one of those, why are you complaining so much? Don't you want to protect the children or stop anti-Semitism or something?"
yep. the whole purpose of this is to stop people from communicating with each other, and only consume approved vetted sources. they'd probably prefer to keep tech out of people's hands entirely (why would serfs need that?!?), but it is too useful for the purposes of surveillance and control.
"But sir! The largest websites on the internet implement Government ID Age Check. Just federate with one of those, why are you complaining so much? Don't you want to protect the children or stop anti-Semitism or something?"