By FANDOM's terms of service, users are supposed to be at least 13 years of age. The Discussions section, which makes up the majority of the FANDOM app, appears to consist of a mainly younger group, but otherwise it's mixed between teens and adults alike.
Thank you, Nova. I just wanted to keep it in the back of my mind for future story ideas, and the target age of audience.
No problem! Also know that any story is technically accepted (as long as they are within our guidelines and FANDOM's), and that if you wanted to write something more adult, we do have a NSFW tag for that.
I'll leave names out of it, but we have a gentleman that frequents the site I believe to be in his sixties, a few I figure are in their forties, quite a few in their thirties (I think), and lots in their twenties.
Although, I'm pretty sure the largest age group by far is and will forever be the teenagers. They come in droves to the site like moths to a flame spouting Jeff the Killer this, Slendorman that, Zalgo Zalgo, Pokémon blah blah blah... All are welcome, though, all above the age of twelve, at least.