Couple of theories to what could be contributing factors:

More male characters in general. [Media has about 2 male characters for every 1 female character](https://womenintvfilm.sdsu.edu/wp-content/uploads/2021/04/2020_Its_a_Mans_World_Report_v2.pdf) (and non-binary character are super scarce), so there are more male characters to ship.

Fetishizing same-gender relationships. You get straight women (and even queer women) who festishize gay male couples the same way you get straight men who fetishize lesbian couples, and since [fanfiction websites' userbases are overwhelmingly female](https://centrumlumina.tumblr.com/post/62816996032/gender), that's the fetishization you'll see more.

Wattpad and FFN don't allow explicit content; AO3 does. So when someone wants to post smut, they'll go to AO3, and because of, well, what smut *is*, it's going to be proportionally more shippy than G- and T-rated fics.

Same reason males flock to f/f anime/manga/movies. It’s hot to them. People say it’s because males are usually better written than females in popular media, which is true. But I think the former is more likely.

Are you aware of ao3's origins? It could very quickly answer your question of why it has more m/m content than others, given the purges that occured in the other platforms leading to it's creation. The interface has little to nothing to do with it, IMHO.

There's quite a lot of legitimate fanwork research out there explaining why slash is such a popular FF pairing, I'd be happy to share links if you're interested.

Hello! I am a SACE student completing the Stage 2 Research Project as part of my studies. My research project question is ‘how does the user interface of AO3 lead to a greater prevalence of M/M fanworks when compared to FanFiciton.Net and Wattpad’, and seeks to explore the topic of online slash fanfiction and fandom culture. I’m posting it here (as well as more general fanfiction subreddits) in order to survey those who read/write gen fics, which will give me a broader range of data.

This survey is completely anonymous and should take no more than five minutes to complete. You are free to discontinue your participation in this survey at any time or to decline to answer any questions. The survey can be found at the link below. Thank you for your assistance.

[https://docs.google.com/forms/d/e/1FAIpQLScbfmZsK3xbE7uVPOuIt4EplkqzOYhm3TzEMPmkDblg37ZzUg/viewform?usp=sf\_link](https://docs.google.com/forms/d/e/1FAIpQLScbfmZsK3xbE7uVPOuIt4EplkqzOYhm3TzEMPmkDblg37ZzUg/viewform?usp=sf_link)

Survey - Why is there so much M/M on AO3?