Try it freeFor fiction writers
Bring the draft you already have. Prosa reads every chapter, builds your story bible for you, and flags the details that don't match, with the passages that prove them.
It never writes a word for you.
14-day free trial, then $25/month unless you cancel. Card required. Your books are never used to train AI, not ours, not anyone's.
Chapter 2 — The Mirror at Greycliff
Aeryn climbed the last of the path to Greycliff, her apprentice Loa a half-step behind, where the headland dropped into a hanging valley no one had mapped in eighty years.
She set the brass quadrant down on the altar stone, her sea-grey eyes narrowing against the glare, and knelt to read the tide her mother, Tessa, had never learned to trust.
Loa hung back at the treeline, quick where Aeryn was exacting, her ink-stained fingers already moving — she had followed Aeryn out of the cartographers' guild two winters ago.
She worked in charcoal now, racing the light that was already going copper over the water, getting the headland down before it failed. Whatever Aeryn read in the tide, Loa would have it drawn.
Brevin, her husband, would be back by dusk with the boat; until then the tide-charts were theirs alone — Aeryn's to read, Loa's to draw, and neither of them willing to leave the valley uncorrected another winter.
Aeryn and her apprentice Loa reached Greycliff. She set the brass quadrant on the altar stone, her sea-grey eyes on the tide her mother Tessa never trusted — exacting where others guessed. She would redraw the tide-charts taken from the cartographers' guild before Brevin returned.
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What our early users are saying
Prosa is such a helpful tool for my ADHD writer brain. It picks up so many details that I forget myself. I've tried so many of the writing software out there and I find Prosa to be both straightforward as well as not the bare minimum. I've been way more confident writing scenes now that I know there won't be details that I may be missing. The best part of it is definitely that it's still your writing and that the dev team is so responsive when you need help.
Incredibly useful! …a “memory-bank” that flags when I remember things wrong is a god-send. Super useful to have one centralised app instead of 5+ different solutions. 10/10!
[Prosa] helped me catch things I needed to fix or improve immediately, even in its very early stages. It stands to be a game-changer for the industry.
The problem
Change one thing early and it ripples to the last page. Every question sends you back through all 84,213 words, and readers notice what slips.
ContinuityCastNamesObjectsBackstoryTimeline
— Chapter twelve —
The Crossing
The ferry knocked at the pier.
Aeryn1 pushed back her
right sleeve2, and the scar
caught the light. Brevin3
had the letter, or she did;
she could not remember which.
Loa set the quadrant4 down
and left it on the stone.
127 / 300
The workaround
Most writers keep their story bible by hand: a doc, a spreadsheet, a corkboard, notes on a phone. It's slow, it isn't writing, and it goes stale the moment the book changes.
Prosa builds it from the book instead ↓
Story Bible
Prosa reads your manuscript and writes the bible you'd otherwise keep by hand: the characters, places and objects in your draft, with the details your book has established, each linked to the page it came from. It's yours to edit. Correct an entry, add a new one, and keep building it as you write.
The stakes
Past eighty thousand words, no one holds the whole book in their head. So you reread, keep notes that go stale, and still miss things. Readers don't.
Aeryn's scar · left wrist
“The scar on her left wrist ached before a storm.”
“She rubbed the scar on her left wrist, counting the cairns.”
“Aeryn pushed back her right sleeve, and the scar caught the lamplight.”
“Loa's thumb found the scar on Aeryn's left wrist.”
Prosa reads every chapter and checks each against the rest ↓
Consistency check
One click and Prosa reads the whole book, looking for places where it disagrees with itself: a scar that changes wrists, a name spelled two ways. Each finding shows both passages, so you decide which one is right. Prosa points; it never changes a word.
Under the Hood
Shepherd is the engine behind Prosa, built and refined over months with real authors. It reads the entire manuscript, works out the whole cast across hundreds of pages, and holds your story as one connected model it can check for consistency, across every chapter of even a very long book. It reads; it never writes.
Your manuscript
Aeryn had her mother's eyes. Tessa was twenty years dead, but the sea-charts she drew still hung in the workshop, and Aeryn read them the way other people read scripture.
Old Halloran had trained her since she was a girl — taught her to feel a coastline in the dark long before she was ever allowed to draw one in the light.
Now Aeryn taught the same trade to Loa, her apprentice, who learned the knots and the bearings faster than she would ever admit to her face.
She had married Brevin at Greycliff, in a chapel that smelled of salt and pitch; he kept the boat, she kept the maps, and for a while that was enough.
Marsala had ridden at her side through all of it, a sworn ally since the guild years — right up until the pass above Tindel, where Marsala turned on her and took the charts for herself.
Every chapter, end to end. Not a sampled excerpt or a summary of the prose.
Who's present, where a scene sits, what's true as of this page, resolved across the entire manuscript.
Each detail it remembers points back to the passage that proves it, so you can always check the work.
Our philosophy
Prosa supports the writer's judgement, memory, and craft. It helps you understand and strengthen the manuscript you wrote.
It does not generate chapters or imitate your voice, and it doesn't replace editors or stand in for revision.
Storytelling is a human art form. Everything Prosa does is in service of keeping stories human.
Your sentences stay yours. Prosa writes notes about your book, never the book itself: not a line, not a chapter, not a title, not character art.
It's never used to train AI models, not ours and not anyone's. Your work stays private to your account and is handled under UK data-protection law. Export every draft, anytime.
Everything Prosa remembers points back to the passage that proves it. You can always check the work.
Plans
$25per month, or $250 a year
Full editor, import/export and fifty manuscripts.
Monthly reading allowance included. Whole-book checks show their estimated usage before you start.
In a paid month, the allowance builds your story bible many times over and covers hundreds of questions. A whole-book check uses anything from a few percent to most of the month, depending on the book. The allowance renews on the 1st of every month, also on annual billing. If a check's estimate is more than you have left, it doesn't start and nothing is used. A trial has the same allowance as a paid month.
Write in Prosa
$0
$10per month, or $100 a year
Both include
Pro's free trial needs a card. After 14 days it costs $25/month, or $250/year if you choose annual, unless you cancel, and its reading allowance is the same as a paid month's. Prices in US dollars. Tax is included, except in the US, Canada and India, where it is added at checkout. Any discount is applied at checkout. Cancel anytime.
Questions, answered
No. Prosa reads what you've written and keeps track of it for you: the cast, the details, the continuity. It never drafts, rewrites, autocompletes or suggests a line, and it never changes your manuscript. It writes notes about your book, never the book itself. The writing stays the writer's.
Yes, to read, never to write. AI models read your chapters so Prosa can build your story bible, answer your questions about the book and check it for contradictions. Every book starts with that reading switched off: apart from suggesting where your chapters begin when you import a file, nothing from a book reaches a model until you turn reading on for it. The models run on providers named in our Privacy Policy, under terms that rule out training on your text or keeping it once they've answered.
Never. Not our models, not anyone else's. Your book is not training data.
Your manuscript is private to your account. It travels to Prosa over encrypted connections and is held only by the services our Privacy Policy names, under UK data-protection law. The one thing we may read to improve Prosa is your questions to Shepherd, with their answers and the passages they quote, and you can opt out of that by emailing privacy@prosa.so.
A Word document (.docx) of up to 50 MB, or a plain-text file (.txt) of up to 8 MB. Prosa suggests where your chapters and scenes begin, and you confirm them before anything is created. PDF import is coming soon.
Long ones. The story bible reads up to 500,000 words, and the consistency check reads every chapter. Prosa reads each book on its own and doesn't carry details from one book to the next, so a series is checked one book at a time. Reading runs within a monthly allowance that renews on the 1st.
Yes. Export any draft as a Word document, or every draft at once, whenever you like and at no charge. Your story bible and Shepherd's answers can't be exported from Prosa yet: email privacy@prosa.so and we'll send you a copy within a month.
Prosa is open to writers based in the United Kingdom and the United States. Your home country is set when you sign up, and you can keep writing while you travel. If you live elsewhere, email support@prosa.so: we can sometimes make an exception.
Free keeps the editor, import and export for one book, and Hobby makes room for ten. Pro adds everything Prosa reads for you: the story bible, the whole-book consistency check, questions about your book, scene readings and search by meaning. Pro starts with a 14-day free trial, which asks for a card, comes with a smaller reading allowance than a paid month and becomes Pro unless you cancel. The prices are in Plans, above. Tax is included, except in the US, Canada and India, where it is added at checkout. Any discount is applied at checkout. Cancel anytime.
Ready when you are
Bring the manuscript you're already writing. Prosa builds your story bible and checks your continuity across every chapter. It reads your story; it never writes it.
14-day free trial, then $25/month unless you cancel. Card required.
Import DOCX or TXT, PDF coming soon · Your words stay yours
