The fanfiction is currently above 16,777,215 words (we don't know the word count because fanfic.net uses 24-bit integers to count the amount of words and this fic surpassed the computational limit), and is 2000+ chapters. It is written by Jamesdean5842 and is still being written to this day.
The story is about an OC named JD Knudson who moves into the Louds town and goes on adventures with them after creating a superhero team with them. According to the recap (Obviously not even close to finished recap) on Tvtropes.org, the fic consists mainly of loud house episode plots rewritten to include the OC and a multitude of crossovers with other franchises from any piece of media you could possibly think of. (https://tvtropes.org/pmwiki/pmwiki.php/Recap/TheLoudHouseRevamped)
Some examples of the crossovers are Ed, Edd n Eddy, Naruto, Dante's Inferno, Inside Out, Matilda, Pulp Fiction, CatDog, Metroid, The Simpsons. This is a very small selection of the crossovers done in the fic.
Despite the fic's main characters being minors, the story contains lots of swearing, sex, romance, drugs, and violence. The sheer amount of strange details about this fic is crazy, reading the TVtropes page will give you some intense mental whiplash. (https://tvtropes.org/pmwiki/pmwiki.php/Fanfic/TheLoudHouseRevamped)
This is just the tip of the iceberg for this story, it is absolutely insane.
Up there with it is the webfiction Wandering Inn, ongoing but currently at 12,246,348 words, making it the longest piece of original English literature, as its OC and not fanfic. (also, I have read all of it )
And, I think "Loud House Revamped" is actually only the longest work of literature in English.
Bringing The Farm To Live In Another World is an ongoing Chinese webfiction, currently with 2584 chapters. And, the Guin Saga is a published work of 171 volumes of Japanese light novels. Neither of these I've been able to find exact wordcount, but both are reasonably likely to be at or above Loud House's 16.8 million words.
(light novels are often pretty short, but the Guin Saga notably has the books pretty thick for the genre, so I'm guessing they're all in the neighborhood of 100,000 words, putting my guess for wordcount at ~17 million; Bringing The Farm To Live In Another World I'm guessing for a chapter length of 10,000 words just vaguely off that that's common for webfiction, and with it on Chapter 2584, that'd put it around 26 million words, but that's a very rough guess)
There's plenty more extremely long webnovesl in japanese in chinese (Edit: and Korean), and predictably, its hard to find exact details on the English web, so please correct me if I'm off here. The format kinda took off there in the aughts, whereas it didn't really take off in the west until the 2010's.
"also, I have read all of it"
Im sorry!?!?!? YOU READ ALL OF IT??????? ALL 12,246,348 WORDS OF IT??? My adhd ass could not do that in a million years unless it was the best piece of media I had ever read.
I'm kinda scatter brained, so usually I'm reading like 5 different things at the same time, often webnovels. But I bounce between things constantly. Also, I've been actively following it for like, 3 years at this point, so a lot of that read-time is just, a chapter, twice a week.
I have never heard of that before, and I am so happy you brought this greatness to my attention. Truly a story of all time
Yea, I don't like the show personally. I think the fact that this fanfic exists and takes the title for the longest written work in english is just nuts.
Reject this shit, retvrn to The Story of the Vivian Girls, in What Is Known as the Realms of the Unreal, of the Glandeco-Angelinian War Storm, Caused by the Child Slave Rebellion
Here is the Down The Rabbit Hole video for anyone who is interested: https://www.youtube.com/watch?v=vjCS_u3Sgpg
You're thinking of Subspace Emissary World Conquest, Revamped quickly caught up to it and surpassed it a while ago.
Jamesdean5842 on fanfiction.net, here is his profile on there (https://www.fanfiction.net/u/5625800/Jamesdean5842)
I have autism
I'm not at all surprised.
(Not making fun or anything, I'm autistic myself. It's just exactly the kind of thing that would take autism to be that dedicated to.)
Something that I found out of the TVtropes page is that the main character of Subspace Emissary's World Conquest make an appearance in Loud House Revamped. The main character of the My Immortal fanfiction also makes an appearance, I lost my shit when I read that, seriously.