Since the end of the Harry Potter books and movies (remember that we’ve disowned the Fantastic Beasts series/movies and J.K. Rowling) there has not been the usual slow-down of fanfiction that usually occurs when a show or book series has finished. If anything, the amount of Harry Potter fanfiction has grown exponentially since the last movie came out. I think this was caused by quite a few reasons. For one, there is a lack of backstory for the canonical characters. We won’t argue over whether this was intentional or slightly-bad writing, but either way, the characters of the Harry Potter series–especially the characters outside of the ‘Golden Trio’–are extremely open to interpretation. This has lead to every possible variation of person and personality possible in fanfiction.
Along these same lines, the Marauders were never given the backstory they rightfully deserved. The best fanfictions oftentimes are about the Marauders’ time at Hogwarts because there are so many extra details that we never heard about their lives. For example, how did they hide becoming animagi? How did James really finally win Lily over? Was Peter always a terrible person or was he actually a good kid? As a fandom we don’t have the ‘canon’ answers to these questions, so fanfiction writers have taken it upon themselves to give us all of the details we’ve ever wanted and dreadfully needed. There’s also magic. This alone breeds a million different possible storylines. The idea of magic in the books is so fuzzy, there doesn’t appear to be any reason why there couldn’t be a spell for literally everything. And the whole wizarding world remains completely unexplored in the books, so there’s so much outside of London and Scotland to explore in fanfiction (not that I don’t love Scotland and London, I really do).
And where there’s magic, there is also the absence of magic. The multitude of characters and lack of story outside of Hogwarts is a perfect combination for every possible AU (alternate universe) you could ever think of. Also, the amount of ships in this series is just truly amazing. In every series, there are a small set of people for every possible ship, even if it’s super niche and there’s only like 4 total fanfiction stories about them (I’ve been there when it comes to Hyde and Jackie in “That’s 70’s Show.” It’s depressing). However, in the Harry Potter fandom, you can be sure that even if only 5 people ship the same people, they have written at least 3 fanfics about them each. It’s truly amazing how much variety I’ve seen in the Harry Potter fandom. I love it so much.
If this hasn’t convinced you to jump into some Harry Potter fanfiction, then I don’t know what will. Although, you could always check out the Fred and Hermione one-shot I wrote back in 2012. It’s awful but in a good way.