To write fanfiction, pick a canon you know well, decide the one thing your story changes or adds to it (a missing scene, a different choice, a new setting), then keep every other canon fact true unless your change breaks it. Write the first chapter short, tag it honestly on Archive of Our Own (AO3), FanFiction.net or Wattpad, and post on a schedule you can keep. Then track what your change breaks: that's where long fics fall apart.
Below: a worked divergence from Pride and Prejudice (public domain, so we can quote it), a ledger you can copy, and the posting limits AO3 actually enforces, read from its own source code on 13 November 2026.
How to write fanfiction: the five decisions
| Decision | What you choose | Why it matters |
|---|---|---|
| 1. Canon | The book, show or game, and which version of it (books or adaptation, which season) | Readers check details against the version they know |
| 2. Type | Missing scene, canon divergence, alternate universe (AU), sequel, crossover | Sets how much canon you must keep |
| 3. The change | One sentence: "What if ___?" | Everything else in the fic follows from it |
| 4. Point of view | Whose head you're in, first or third person | Fan readers come for one character's inside |
| 5. Where you post | AO3, FanFiction.net, Wattpad | Each has its own ratings, tags and rules |
Book Riot's guide (Andy Minshew, 15 Dec 2021) splits fics into in-universe and AU; Wattpad's (22 Feb 2023) lists five types. Neither says what to do once you've picked one. The third decision is the one that has consequences, chapter after chapter.
Choose your divergence point, then find what it breaks
A canon divergence fic keeps the world and changes one event. The trap: canon events lean on each other. Change one and later scenes quietly stop making sense, which is the thing commenters notice first.
Here's a worked example. In Pride and Prejudice, Darcy's first proposal opens Chapter 34 ("In vain have I struggled. It will not do."), and Elizabeth refuses: "You could not have made me the offer of your hand in any possible way that would have tempted me to accept it." We counted where the big turns fall in the Project Gutenberg text, measured in words from Chapter 1 (122,412 words of novel):
| Canon event | Chapter | How far through the novel |
|---|---|---|
| First proposal, refused | 34 | 48.1% |
| Darcy's letter explaining Wickham | 35 | 49.8% |
| "Till this moment, I never knew myself" | 36 | 53.2% |
| Lydia runs off with Wickham | 46 | 69.1% |
| Second proposal, accepted | 58 | 94.0% |
Source: KudoNovel's count of Project Gutenberg eBook #1342, 13 November 2026.
So a "she says yes" AU throws away the back 52% of the book: half a novel of canon you now replace or re-route.
The divergence ledger (copy this)
Before chapter one, fill in one row for each canon event after your change.
| Canon event | Still happens? | Changed how | What your reader must still believe |
|---|---|---|---|
| Darcy's letter (Ch 35) | No: he has no reason to write it | Elizabeth never learns Wickham's history from Darcy | She's engaged to a man she half-misjudges |
| "I never knew myself" (Ch 36) | Not yet | Her self-reckoning moves later, inside the engagement | Her pride is the fic's real obstacle now |
| Lydia's elopement (Ch 46) | Yes | Darcy is family by then; the scandal lands on his name too | Wickham is still Wickham |
| Second proposal (Ch 58) | Replaced | The climax becomes whether the marriage survives the truth | The ending is earned, not handed back |
"Still happens?" catches the events you forgot depended on your change. "Changed how" is your plot. "What your reader must still believe" is the character check: Wickham doesn't become a good man because your timeline moved.
For a missing-scene fic the ledger is shorter (what's on either side of your scene and what it can't contradict). For a full AU (coffee shop, modern, fantasy) list each character's traits instead of events: an AU changes the world and keeps the people.
Keep characters in character
AO3's terms say what counts as transformative: a fanwork that "reframes existing material in a unique manner, such as retelling a superhero movie from the perspective of civilians" (AO3 Terms of Service FAQ). A different person wearing the character's name isn't a reframe, and readers say so in the comments.
Three checks:
- Speech. Pull five lines the character actually says in canon and read your dialogue against them. Elizabeth teases; she doesn't gush.
- The choice test. In your big scene, would canon-them make this choice for this reason? If your answer is "because the plot needs it", give them a reason they'd recognise.
- Facts. Ages, eye colour, family, who knows what and when. Write them down once, because chapter fifteen is where they slip. Our guide to why an AI fanfiction writer drifts off canon covers the same problem when a model writes the drafts.
First chapter, summary and tags
- Open inside the change. Readers clicked for your "what if", so get to it in the first scene: the proposal, the yes, Darcy's face. Backstory the canon already told them can wait or go.
- Chapters: AO3 sets no word target (anything from 10 to 510,000 characters posts). A length you can repeat on schedule matters more than the number.
- Summary: you get 1,250 characters on AO3. Lead with the change in canon's terms ("Elizabeth accepts at Hunsford"), then the question the fic asks. Readers filter on it before they read a line.
- Tags: fandom, relationship, characters, then the type (Canon Divergence, Alternate Universe, Missing Scene) and the tropes. Up to 75 of your own, but tag what's on the page.
- A canon still airing (a show mid-season, a manga still running): put "spoilers through season X / chapter Y" in the notes, and decide whether new canon gets folded in or your fic becomes an AU on the day it's contradicted.
- Before you post, one reader who knows the canon catches the facts you slipped on; how to find beta readers covers where fan writers look.
What fanfic writers search for
What people type tells you where new fic writers get stuck. Monthly US searches from Google Keyword Planner, pulled 13 November 2026:
| Search | Per month | Trend (last 3 months vs the 3 before) |
|---|---|---|
| how to write fanfiction | 1,300 | ×1.26 |
| ai fanfiction writer | 1,600 | ×0.74 |
| tips for writing fanfiction | 260 | ×1.28 |
| how to write fanfiction on ao3 | 30 | — |
| how to write fanfiction for beginners | 30 | — |
| is writing fanfiction illegal | 20 | — |
| fanfiction writing app | 40 | — |
Source: KudoNovel's keyword data (Google Keyword Planner, US), 13 November 2026.
Searches for writing fanfiction yourself rose about a quarter over three months; searches for an AI fanfiction writer fell by a quarter.
Is writing fanfiction legal?
AO3's position, in its terms FAQ: copyright protects "an individual's expression of an idea, not the idea itself", so a transformative fanwork "does not require the copyright owner's permission to create or share." What it won't host: "someone else's work" with "only minor changes to it (such as swapping out the names, changing the formatting, or rewording the original text)." Quote canon in short lines, the way this page does; don't paste chapters. That's AO3's reading of US law, not legal advice.
Posting on AO3: the limits its own code sets
AO3 is open source, so its rules are readable in its code (we read the version of 1 November 2026). Note first: AO3 went offline on 29 October 2026 after a security incident, and as of 13 November we found no report that it's back; our page on AO3 alternatives while it's down tracks it.
| Field | AO3's limit | Source in the code |
|---|---|---|
| Work title | 255 characters | TITLE_MAX |
| Summary | 1,250 characters | SUMMARY_MAX |
| Beginning or end notes | 5,000 characters each | NOTES_MAX |
| Chapter text | 10 to 510,000 characters | CONTENT_MIN, CONTENT_MAX |
| Your own tags | 75 per work, 150 characters each | USER_DEFINED_TAGS_MAX, TAG_MAX |
| Unposted drafts | Deleted once more than 30 days old, by a daily job | work:purge_old_drafts |
Two of these catch new writers out. Drafts: a fic saved as an AO3 draft and left for a month is gone (the task deletes unposted works created more than 30 days ago). Draft somewhere you keep. Ratings: "Individual chapters of a work cannot be rated separately, so the rating chosen should be sufficient to cover the highest-intensity content in the work." One Mature chapter makes the whole fic Mature, or you pick "Not Rated". The ratings run General Audiences, Teen and Up, Mature, Explicit and Not Rated, and AO3 says it "will never remove a fanwork on account of its quality, length, grammar, spelling, or punctuation."
Wattpad and FanFiction.net work differently on ratings and AI; which story sites allow AI fiction and Wattpad fanfiction's rules have each site's own wording, dated. To get your fic back off any of them, see fanfiction export.
Where the posting sites fall short as a place to write
AO3, FanFiction.net and Wattpad are where readers are. They're poor places to keep your only copy:
- AO3 deletes drafts after 30 days (above), and since 29 October 2026 the whole site, drafts included, has been unreachable.
- None of them tracks your canon. A divergence ledger, character facts and nicknames live in a separate doc you update by hand, and a doc you have to remember to update goes stale by chapter ten.
- Their editors are posting forms. Chapters are pasted in one at a time; there's no running record of what each chapter changed.
Write it in KudoNovel, post it where your readers are
KudoNovel is a better place to write the fic itself. Your ledger goes in as notes, yellow stickies on the page that aren't part of the book, and Expand and Steer read the notes near the paragraph they're working on, so "Darcy never wrote the letter" is in front of the AI every time. The story bible keeps each character's canon facts with aliases (Lizzy, Eliza, Miss Bennet are one person) and updates itself as you write; an entry you wrote or edited is never rewritten by the AI. Type a rough line, press Expand, and it becomes prose from your words, with every version kept under Undo.
On purchased credits, the KudoAI agent can look a canon up on Wikipedia or a Fandom wiki and fill the bible from it. A fic you've already started imports from .docx, .epub, .md or a zip of chapters, and the finished one exports as plain text, Markdown or EPUB to post anywhere, or goes up on KudoNovel's Community Books chapter by chapter. Everything saves to your account as you type.
Fill in your ledger, then start your fic in KudoNovel on the free credit you get after confirming your email; after that it's one-off credit packs that don't expire, no subscription.