AO3 a fanfiction site that is largely romance, some of it explicit, some of it not, and more popular with girls than with boys, but definitely readers from all slices of life reading all sorts of genres
but they are notable for taking a hard freedom-of-speech stance on you can post extremely hardcore or problematic erotica as long as it's clearly tagged, stuff that most sites would ban and delist. This means they have to control all their own infrastructure to avoid censorship pressure while also on a shoestring volunteer budget, which is why they're now facing a large downtime after an attack, as they can't just click a cloud deploy button.