How to write fan fiction: canon, characterization and AUs

Fan fiction is fiction built on someone else's foundation, and Wikipedia's article pins the definition to that relationship: a fan work either stays within the boundaries of the source's canon without being part of that canon, or sets out into an alternative universe. It is written by fans, for fans, and, in the article's flat observation, "does not usually cater to readers without knowledge of the original media". That clause is the craft in miniature: your reader arrives knowing the characters almost by heart, which raises the bar on characterization and changes everything else. (The glossary entry covers the term; this guide is the writing.)

The form is older than the web. The term appears in print by 1938, for amateur science fiction set against "pro fiction". The modern fandom form was defined by Star Trek fanzines, beginning with Spockanalia in 1967, and women were the primary authors, 83 percent by 1970 and 90 percent by 1973. The internet then scaled it: FanFiction.Net launched in 1998 as an archive anyone could upload to in any fandom, and one estimate the article relays puts fan fiction at a third of all book-related content on the internet. The commercial exits are real and rare: Fifty Shades of Grey began as Twilight fan fiction and Anna Todd's After as One Direction real-person fiction, both "pulled to publish" under new names.

Canon, fanon, headcanon

Three layers, and the writer who cannot tell them apart is the writer whose story surprises the wrong people:

• Canon is the original source: plot, setting, characters, everything the rights holder published.
• Headcanon is one fan's private interpretation; it can build on subtext, but it cannot directly contradict canon.
• Fanon is headcanon that spread: ideas so widely adopted the fandom treats them as fact, with no endorsement from the source (fanon).

The craft discipline that follows: know which of the facts in your head are canon, which are fanon and which are yours. Fan fiction readers keep ledgers, and a chapter that unknowingly treats fanon as canon, or contradicts canon by accident rather than by choice, reads as a mistake rather than a take. This is the story bible discipline under another name, practiced in public, on a canon layer you share with everyone.

Choose your canon relation

The long-running TV Tropes guide to writing fanfic sorts every fan work into one of five relations to canon, and the sorting is the first real decision:

• Adaptation. Retelling an existing story in prose, best with plot-thin sources, energized by a new angle: the villain's view of her defeat, the bystander's view of the climax.
• Continuation. More story in the canon's own style, after the end or between events. The widest-audience choice, and the one that demands command of the whole work.
• Divergence. One deliberate "what if" on a crucial detail; the story measures the canon by changing one variable. What if the antagonist was right all along?
• Elsewhere fic. The setting without the main cast: new characters in the established world, still bound by the world's established rules.
• Alternate universe. The inverse: the canon cast in different roles and often a wholly different setting, with the canon plot discarded entirely.

Divergence and AU get confused constantly; the working distinction is that divergence keeps the canon and changes one event, while an AU keeps the characters and replaces the world. The guide's advice for beginners is adaptation with small continuations to learn the canon's grain, plus a warning worth keeping: cultivate a personal style, because imitation alone leaves a work with nothing of its own.

Characterization is the whole game

Everything in fan fiction stands on borrowed characterization, and the two named failure modes are opposite sins:

• Out of character. Anti-heroes do not turn sweet because you like them; characters do not turn villainous because you dislike them. The subtler failure the guide names is characters who never contradict their personalities but never do anything distinctive either, and so read as generic. The test is not only "would they never say this" but "would only they say this".
• The Mary Sue. The term originated in a Star Trek fan fiction parody of wish-fulfillment stories: an idealized, overpowered, flawless character widely read as the author in costume (Mary Sue). Its relations include the careless self-insert and the favorite canon character promoted to the center of everything. The cure is the cure for any character: flaws that cost something, and a real arc.

Spotlighting a side character, giving the ensemble dark horse or the resident Terrible Trio their own story, is encouraged by the same guide, with the caution that loving a character too much is its own distortion.

The AU toolkit

The article's own range for alternate universes runs from dramatic setting changes (a fantasy AU) through characterization changes (usually labeled out of character rather than an AU proper) to changed plot events, the fix-it case. The standard structures, from the same sources:

• Fix-it fic. Rewriting canon events the author disliked: plot holes, tragic endings, the "everyone lives" AU.
• Time travel AU. A character sent back with knowledge of the plot, called "Peggy Sue" after the film, or the "Groundhog Day" loop that repeats until the traveler gets it right.
• Soulmate AU. A world very like canon except soulmates are real and mechanically visible, names on skin or the first touch, with the standard engine of a character convinced they have no soulmate.
• Crossover and fusion. Characters or worlds from multiple fandoms meeting, or two universes merged into one (crossover).
• Uberfic. An AU far enough out that the characters keep faces and personalities but gain new names and settings; the form has a publishing history of its own, Xena uberfic legally published as original lesbian fiction.

The AU craft rule from the guide: different setting, same people. Stay true to the characters' personalities and gimmicks despite the new setting, because an AU that changes the characters too has discarded the one thing the reader came for. An AU is a controlled experiment: the cast is the constant, one variable changes, and the story is what the change proves (alternate universe).

Romance, and shipping without the red string

Shipping is fan fiction's romance engine (shipping), with slash fiction and femslash as its historical same-sex subgenres, and romance the most common genre in the form. The named failure is "strangled by the red string", pairings that snap together without earning it. The guide's instruction is to work out the dynamic before writing the pairing, because old friends falling in love, a stalker whose interest is returned, and enemies overcome by mutual lust are three different stories in three different registers. Then check what your fandom has already done: if your pairing has hundreds of hurt/comfort stories, hurt/comfort is the crowded room.

Finishing: the dead fic problem

The guide's blunt statistic: "90% or so of multi-chapter fanfics will fail to finish." The questions it prescribes before starting one are worth quoting as a self-audit. Am I writing primarily to receive reader feedback, and how will I take silence? Do I still enjoy the source as much as I used to? Do I have the time in my life to commit? How confident am I in my writing? Do I have a plan, or am I starting just to see where it goes?

The structural advice around that number: start smaller than the epic, a one-shot or an eight-chapter piece first; plant a turn in every chapter rather than saving the one twist for chapter eighty-six; and write in arcs with breather episodes, because trying to increase the awesomeness steadily is how epics burn their authors out. Serial writers will recognize all of this; it is choosing a release schedule and chapter endings in fandom clothing.

Posting etiquette

• Summary. Most archives display it on the index page; intrigue, do not soundbite. Outline the premise rather than the plot, and never write "I'm bad at summaries", which some readers take as evidence about the story. AO3's own tutorial describes the field as the back-of-book blurb (how to write a book blurb).
• Title. Short and simple; obscure poetry lines and awkward phrasings make a story hard to remember and hard to recommend.
• Author's notes. Never inside the story; beginning or end, visually distinct, short, and spoiler-free, with no long apologies for lateness. AO3's posting form offers exactly those slots, notes at the start, the end, or per chapter (author's notes on serial platforms).
• Warnings and tags. Fandom's trigger-warning culture runs deeper than any platform's minimum, but the platform minimum is real: AO3 codified four core warnings (graphic violence, major character death, rape, underage sex) and requires authors either to disclose or explicitly to decline to disclose (how to post fanfiction on AO3). The fandom intensifier "Dead Dove: Do Not Eat" means precisely that the other tags mean what they say.
• Disclaimers. The old "I don't own these characters" notes have no legal effect, and the article records that they have fallen out of use since AO3's rise.
• The source creator's stance. The copyright debate is genuinely unsettled, and authors range from welcoming, Rowling and Meyer among them, to hostile, Martin and the late Anne Rice, who had works based on hers removed from FanFiction.Net. Before posting in a fandom, check where its creator stands; it is etiquette and risk management at once.

Why a novelist should bother

Fan fiction is characterization training under constraint: the cast is fixed, the reader's standard is encyclopedic, and the feedback is immediate. It is also a pipeline, from Spockanalia to the bestseller lists, and the pull-to-publish route, serializing in fandom and converting to original, is a real if rare path (publishing paths). What transfers is the canon discipline: tracking what the source established against what you invented, the exact skill a long original serial also runs on. Writers arriving from original fiction already have the story bible habit; writers leaving fan fiction for originals have the vocabulary (fandom, fanon, shipping) and need the new work of naming their own characters and building canon nobody else knows yet.