It's fairly easy to do because, if you've been on Twitter and you've tried to find porn, you will see that there's a page that announces that sensitive content is coming.
Twitter knows where it is, so it's easy to find and it can be age-blocked, age-verified—all of those things work.
I would also expand on this analogy that children can't go in a bar and drink, but they are allowed to go to a restaurant. The server is not allowed to give them a drink.
It's not so much where, but it's the pornographic content that we're aiming at. This is where it has to be stopped because it's obviously not only with porn sites, but also on social media platforms.
This is where, many times, children have their first opportunity—even pops-up—to see pornography.