The principle
You write. You decide.
Your work stays yours.
CollaDuet is a writing environment for authors working on one or more books, solo or together. Every sentence comes from human hands; you decide where everything lives, local on your own machine or in your private vault online; and nothing of yours ever goes anywhere without you choosing it. Below: five features, one subject each.
Writing
A writing sheet that thinks along — and a manuscript you can open as a book at any moment.
Capitals and quotation marks sort themselves out; the Codex recognises your characters the moment you type them. Once you've written, you can open your text as a book to read at any moment.
Writing together
Two cursors in one sentence — and still the main text stays whole.
Iterate on a sentence or paragraph together, or write live in the same scene — no problem. If you or your co-author want a new plot twist or a complete scene rebuild, you open that as a pencil in the margin. From the pencil you choose: replace, insert, or leave it as it was. Even a week offline: through the pencil function you merge it all back together yourself.
Margo
A reader-along who warns you when something doesn't add up — and never writes a word for you.
Margo runs on your own computer, knows your story, and points out what jars right where it happens. The fix, you type.
Your world
Your story world in one place: map, timeline, characters and scratch pad.
The Codex keeps track of your characters and places, the Atlas gives them a globe, the Plot Board the through-line — and Notes catch every stray idea, never inside your text.
Your work
Local-first, and yours from day one.
Your work lives on your own machine and never leaves. If your subscription stops, only the syncing stops; you keep writing the same day, for free.
Wherever you are
Your writing place travels with you.
Writing doesn't only happen at your desk. A sentence in the waiting room, an idea on the bus — CollaDuet is there wherever you are, on every screen you carry. CollaDuet doesn't ask which device you have. You open it in your browser and carry on where you left off.
Silence is a feature.
No advertisements. No messages inside your work. We only speak up when it truly matters. Otherwise: write.
CollaDuet›Features›Story Builder
What is CollaDuet?
Writing with tools
that think along with you.
CollaDuet is a professional writing application for writing books, supported by professional tools — on your own, or together with one or more co-authors. That writing happens around a key feature we call the Story Builder. Many successful writers develop their characters, their world and their story around research, ideas and facts. That exact way of working is something you can do fully in CollaDuet: plot building, relationship networks, character descriptions and much more.
All these elements are connected in the Codex. This feature, running quietly in the background, supports you as you write: known elements from your Story Builder are underlined and reveal their details on hover. Another handy feature, Margo, helps you keep your story consistent — all those details about the world you're writing about are watched over, like a kind of editorial system. So you can focus on nothing but the writing.
CollaDuet is built, above all, to develop your book methodically and systematically. Read on below about the various tools and how they work. Enjoy CollaDuet.
Story Builder & Codex
Your book world grows with you.
Story Builder and Codex.
In the Story Builder you set down the whole world of your story. You decide who your characters are, their personalities and backgrounds, but also the elements that matter to your story: lands, peoples, religion, economy, objects and artefacts. By filling the Story Builder, the Codex takes shape — the reference work of your story — and all these elements then return as you write.
And on the sheet it all comes together: CollaDuet recognises the names from your world in your text and highlights them. One click brings the knowledge alongside — who someone is, what that place looked like, what you decided earlier. Writing on without searching. And if chapter nine names your tavern just a little differently from chapter two, Margo will point it out.
As you write, you seamlessly add new characters, objects, lands or words to the Story Builder. So you build while you write.
The sheet, the Canon, is your writing surface in CollaDuet, always readable as a printed page. The Codex is the reference work CollaDuet keeps of your characters and places on its own.
The sheet thinks along
Small conveniences.
Great calm.
Capitals that sort themselves out. Quotation marks that bring their other half. And the Codex recognises your characters the moment you type them. Hover over a recognised name to see the details. Watch the example — we'll show you.
The book reader
Watch your book take shape.
While you write.
A sheet on a screen stays a promise. So at any moment you can open your work as a book — cover, table of contents, pages that turn, and the page layout showing exactly where on the page your words fall. Even someone who never wrote before can see today where it's heading.
You're always free to leave.
Don't start from zero: bring your existing manuscript along — paste it or import a file, and CollaDuet pours it into chapters and scenes. And getting out is always just as easy: export your whole project, or your book as a PDF or EPUB — complete, unlimited, even if you stop. Full circle, in a single action. The goal, after all, isn't a file but a book.
Glossary
- The sheet
- Your writing surface — always also readable as a printed page or an open book.
- The Codex
- The reference work CollaDuet keeps of your characters and places on its own, and recognises in your text.
- Page layout
- The view that shows where on the printed page your words will fall.
CollaDuet›Features›Writing & writing together
Writing & writing together
You come back on purpose.
Always your choice.
CollaDuet is 'Offline Forever', and when you buy CollaDuet Author it's yours, forever. Writing solo may go on endlessly; we never see anything of what you do, your work stays with you, private, for as long as you want.
'Online together - Native' means writing and working together at the same time, whatever your operating system: in the same scene, in different scenes, or in different parts of CollaDuet. Our promise: you choose, at any moment, that you can work together with others in CollaDuet. Write offline for a while? On your return your work doesn't slip silently in somewhere — you edit together with the CollaDuet Pencil function, right where all the new text lands.
Collaboration requires, perhaps regrettably, online technology. But our online service is built so that your work isn't only well protected with encryption — the key to that encryption lies with you. We can never decipher your work. And whatever the situation: the local app you use while collaborating always keeps a working version on your own device. Lose access to the internet or to each other, and you keep your work. On top of that, you can export your work any second, on your own time, and secure it somewhere — not unwise, should your device ever give out.
The why
Nothing gets lost — and you see exactly what came together, spot by spot.
Write for a week by the lake, out of range. Come back online, and your work arrives with your co-author: marked in your colour, with one 'Pencil note' in News, and a walk spot by spot past everything that came together. Because working on a book together means you want to see what the other did — and you decide what to do with it: read, respond, or tick off.
Silent syncing might feel like magic — but having to wonder what actually happened is not what you want. So CollaDuet shows you.
The canon is the one main text that is sacred; that's what you write on together. A pencil is a proposal on a sheet beside the canon, waiting in the margin until you choose.
Pain workflow · together on one text
Two people, one document — and yet three versions, an overwritten afternoon, and the question "whose sentence wins?"
You know the drill: one works in "the latest version", the other in a different one, and in the evening someone has to merge by hand. Waiting for the other to finish. Or worse — accidentally overwriting an hour's work.
How CollaDuet handles it
There is one main text that stays sacred: the canon. If your co-author wants something different, they don't write inside your text, but with a pencil — a proposal on the sheet beside it, waiting in the margin until you choose. Block by block: take it or keep it. No versions, no overwriting.
He thought of the letter, of the seal that broke when no one was looking. Outside the rain fell straight down.
at a slant across the cobbles
of the promise he had not wanted to make
Pain workflow · offline and visibly back
Written for a week out of range — and then the cramp: will this really come together, or will I lose something?
Inspiration doesn't wait for wifi. But writing together and going offline feels risky: you don't know whether your work comes back whole, or slips quietly in somewhere.
How CollaDuet handles it
Offline may go on endlessly, and nothing gets lost. On your return your work doesn't slip in silently — it arrives: marked in your colour, with one message, and a carousel that leads you spot by spot past everything that came together.
Nothing gets lost, and you see exactly what came together — spot by spot.
The model
How coming back works.
While you write offline, CollaDuet simply keeps everything with you — text, new scenes, pencils. As soon as you're connected again, three things happen, on their own:
- Your work travels to your co-authors and appears in their manuscript, marked in your colour — exactly at the spots where you wrote.
- One message appears in News: "Wilfred is back: 6 passages in 3 spots." Not six separate notifications — one.
- The carousel opens the walk: click, and the manuscript jumps to spot 1 of 6. Read it? Tick it off, jump to the next. Ticking off is personal — your ticks dim your markings, your co-author's dim theirs.
There's no more admin than that: no one has to approve anything, no one can miss anything. If you want to respond, you do it right there — with a pencil or in the chat.
Pain workflow · revising without a battlefield
Revising together feels like a battle: struck-through lines, balloons in the margin, and no one who can still see what the text is now.
Proposals and corrections pile up inside the text, until the markings make the sentence unreadable. Accepting or rejecting becomes guesswork.
How CollaDuet handles it
A pencil isn't a strike-through inside your sentence, but a complete version alongside it — readable on its own. You decide block by block, while the canon stays whole and readable. And in the same scene you watch each other's cursor grow, each in its own colour; your undo stays yours.
The shared memory
News: the shared memory of your book.
News is where all notifications arrive: Margo's, and when you collaborate those of your co-authors, of comments, of pencils and more. A smart system takes you from every notification straight to the spot in your text, so you quickly set everything right again. Every item is clickable and travels to the spot itself — you never read about your book without being able to get to it. Handled is handled: what you tick off vanishes from your list (and only from yours).
So you begin every writing session with thirty seconds of News and know exactly where the book stands — even after two weeks away.
Staying in touch
Chat and VideoDuet.
Simple features that help you stay in touch while you work together — without having to reach for an external app. You can shrink the panels and drag them wherever they're out of the way.
Glossary
- The canon
- The one main text that is sacred; that's what you write on together.
- A pencil
- A proposal on a sheet beside the canon, waiting in the margin until you choose — block by block.
- The carousel
- The round past everything that came in, while the manuscript jumps along with you to each spot.
CollaDuet›Features›Margo
The Margin function: Margo
Margo notices it.
You decide.
Margo is CollaDuet's editor: a mini-AI that runs on your own computer, knows your story and warns you when something doesn't add up — but never writes a word for you. Her name comes from the Latin margo: the margin, where she lives.
Margo reads along
Right where it happens.
With the source alongside.
Margo gathers and records inconsistency notices in your News bulletin. Each notice takes you to the spot in your text, and there you decide what to do: change it, remove it, leave it, or confirm it. You type the fix — Margo changes nothing herself.
At first light he left Norwyn, the letter pressed to his chest.
I'll change itDeliberate — ignore
Several smart Margo functions.
CollaDuet allows for several smart Margo functions — you decide how far you go.
- Codex and small inconsistencies — not AI, but a smart function that is always there and helps you keep an overview based on your world description.
- The Margo Margin function — if your laptop is powerful enough, you can choose to install and connect a small AI model yourself. In this function, parts of your Codex descriptions are drawn in during the inconsistency checks.
- AI in the Chatbox — CollaDuet has a chatbox for chatting with other authors. You can add AI here and ask questions about your book in relation to your Codex.
You decide how smart.
Using AI is your own choice and stays limited to editorial work. Its power and effectiveness are set by the computing power of your own device: if it's powerful and modern, a smarter model can be used; if your machine is older, Margo's basic function is already fine to work with. You decide.
Glossary
- Margo
- The editor that runs locally and warns on contradiction — named after the Latin margo, the margin.
- Story Builder
- Where you set down your story world, so Margo knows what holds true in your story.
- Codex check
- Margo's smart function without AI — always present, keeping an overview based on your world description.
- Margin function
- A small, local AI model you connect yourself; draws parts of your Codex into the inconsistency checks.
- AI in the Chatbox
- Asking questions about your book in relation to your Codex, in the chatbox where you also talk with co-authors.
CollaDuet›Features›Your world
Your story world
Your world keeps turning.
Even while you sleep.
Atlas, Timeline, Plot Board, Relationships, Planner and Notes — everything that lives beside your text, in one place.
The Story Builder is where you set down your story world. A Note is the scratch pad beside your text: as a note, sketch or board, never inside your manuscript.
The why
Everything that lives beside your text — in one place, and quietly kept consistent.
A story world grows faster than one head can keep up with: names, places, who-when-where, and the stray ideas you jot down at night. CollaDuet gives all of it its own room beside your manuscript — the Story Builder — so your text stays clean and your world stays true at the same time. Three places where that chafes, and how CollaDuet catches it.
The Codex is the reference work CollaDuet keeps of your characters and places on its own. The Atlas is the map room, on a globe that is yours. A Note is the scratch pad beside your text — never inside your manuscript.
Pain workflow · from scattered fragments to a manuscript
Your story began in chats, notes and loose scenes — and now no one remembers which name came from where, or which eyes your protagonist has now.
Turning a tangle of conversations and documents into a consistent book is exhausting: characters contradict themselves, places shift, and the lore frays. You page endlessly back to check what you agreed three chapters ago.
How CollaDuet handles it
Just bring existing work in and give it structure. The Codex keeps track of your characters and places on its own and recognises them in your text — click a name and you see at once what you set down about it. The Story Builder is the source Margo checks your world against, so a contradiction stands out before your reader finds it.
Pain workflow · a world you can't hold in view
You've invented continents, cities and seas — but which way is the harbour again, and how long does a rider take on that journey?
Without a map, geography becomes guesswork: travel times don't add up, a city sits in the north in one scene and the south in another, and your reader feels the seam.
How CollaDuet handles it
The Atlas is the map room of your story: continents, cities, seas — or planets and moons — on a globe that is yours. And Margo reads along with the map: whoever arrives in Tor Halden in chapter seven doesn't quietly leave from a different city in chapter eight.
Pain workflow · scratch that pollutes your manuscript
An idea, a plot thread, a 'watch-this' — you write it in the middle of your text, and later your manuscript is full of scribbles that don't belong.
Notes, alternative plot lines and quick sketches land inside your prose, or vanish into a loose document you never find again. You don't dare delete, so it stays.
How CollaDuet handles it
A Note is CollaDuet's scratch pad: everything that belongs beside your text — as a note, a sketch, or a board with index cards. One layer, three forms, and never inside your manuscript. Every note gets a label (plot, research, or your own) and a date, is searchable and filterable by label, and stays entirely private — Margo never reads it. Is an idea getting serious? Then you push it through to the Planner with one click. For plotting, you string the through-line between characters on the Plot Board: who knows who, who betrays who.
He thought of the letter, of the seal that broke when no one was looking. The bell of the old tower struck seven.
What if the letter is a forgery — and Systinelle has known all along?
🏷 plot
Plotting on cork
How to use the board.
Drag characters onto the cork as index cards, string threads between them and write on each card what the reader doesn't know yet. If you get stuck on the plot while writing, slide the board next to your manuscript: the cards and threads stay exactly where you hung them. The board doesn't judge and doesn't order things on its own — it's cork, and you do the pinning.
Who relates to whom, and how
Relationships: your whole network in view.
Characters in your story have relationships with each other — friends, family, enemies or partners in crime. But they also have relationships with lands, organisations and objects. With CollaDuet's relationship system you bring your entire relationship network into view, and group the families that belong together.
But stories develop, and so do relationships. An enemy can suddenly become an ally, friends can vanish, an object can take on a different meaning. The relationship system lets you build new views over time that you simply save and load whenever you need them. The characters, peoples and places from your Story Builder are already there; you draw the lines between them, and the map remembers them.
When did what happen
The Timeline: your story in order.
Give events in your story a moment — a date from your calendar, not ours — and the Timeline lines them up. At a glance you see whether the siege really falls before the wedding, and how much happens in that one year. The Timeline is also a source for Margo: whoever arrives in chapter seven can't have left yesterday in chapter eight — and if your text says so anyway, you'll hear about it, with the Timeline cited as the source.
Your scene board
The Planner: from "oh yes, this too" to a card on the board.
Every scene is a card on the board: planned, in progress, done. Drag them into the order of your book, hang a line on each about what needs to happen ("Aldric discovers the seal"), and see at a glance where the manuscript stands — and what still needs writing. If you write together, the board is also the quiet division of labour: you see which scenes your co-author picked up without having to ask. From a margin comment or a note, you push something through to the Planner with one click.
Glossary
- The Codex
- The reference work CollaDuet keeps of your characters and places on its own.
- The Atlas
- The map room of your story, on a globe that is yours.
- The Plot Board
- Your cork pinboard: characters on index cards with the through-line strung between them.
- Note
- The scratch pad beside your text — note, sketch or board — never inside your manuscript.
- Relationships
- The map of connections: characters and places from your Story Builder, with the lines you draw between them.
- The Timeline
- Your events in order, on dates from your calendar — also a source for Margo's consistency check.
- The Planner
- Your scene board: each scene a card (planned · in progress · done), draggable into the order of your book.
CollaDuet›Features›Your work
Your work & privacy
Local-first.
Yours from day one.
Data like Water: your work flows out when you want it to, never when you don't.
Local-first means your work lives on your own machine and keeps working there — with or without internet.
The why
Your work lives with you — and flows out only when you want it to.
Local-first means everything you write sits on your own machine and keeps working there, with or without internet. No service holding your work hostage, no model learning from your sentences. Three places where that usually pinches — and how CollaDuet does it differently.
Local-first: your work lives on your own machine and keeps working there, with or without internet. Data like Water: your work flows out when you want it to, never when you don't.
Two vaults
Your work in a vault — on your machine, and soon online too.
The local vault is the default and works today: everything you write sits on your own computer and keeps working there, with or without internet. Export is always possible, everything.
The online vault is the next step — a small option on top of your edition: your saved work then leaves your computer encrypted, with a key only you hold, so you can carry on from any device without anyone else being able to reach it.
That online vault is in development. Until it arrives, shared text travels encrypted across our EU servers — the honest three-way split below explains exactly who sees what. We promise no more than we can stand behind.
Pain workflow · where is my book, really
You've written a story for years — but where does it really sit as yours now, and who's looking over your shoulder?
Work that lives in a service you can lose to a cancellation, a price change or the small print. And the question gnaws: is my text being used to train something?
How CollaDuet handles it
Your work sits local on your own machine and stays yours — no account phoning home, no model learning from your text. If your subscription stops, only the syncing stops; you carry on writing the same day, for free, in your local edition.
Pain workflow · taking your work whenever you want
You want to export your manuscript or switch — and find it's stuck in a format only that one service reads.
Being locked to one service makes you dependent: your text sits trapped, and getting it out costs hassle, quality loss, or simply won't work without a subscription.
How CollaDuet handles it
Taking it along is always possible: export your whole project, or your book as a PDF or EPUB — unlimited, even without an active subscription. Your work is never held hostage. And deleting we do together: work that several authors wrote on goes to the archive with a notice, never quietly gone.
Pain workflow · is my text used for training
You write something personal — and the quiet question lingers: who's reading this, and will I end up in a training set?
Often it's unclear what happens to your words: stored, analysed, resold or used to feed a model. The small print changes, and you only notice afterwards.
How CollaDuet handles it
Three kinds of data, honestly kept apart. Your text sits locally and goes only to co-authors you deliberately share with, via encrypted syncing over EU servers. Your account (only when collaborating) is the minimum that makes sync possible. Statistics we keep to the strictly necessary. We promise no more than we can stand behind.
Glossary
- Local-first
- Your work lives on your own machine and keeps working there — with or without internet.
- Data like Water
- Your work flows out when you want it to, never when you don't; export is always possible.
- The archive
- Where shared work goes instead of quietly disappearing — with a notice to everyone who contributed.
CollaDuet›The story
The story behind CollaDuet
Two authors, one trilogy,
and a tool that didn't exist yet.
We built CollaDuet while writing in it ourselves. The logbook from the workshop — and below it, the origin series in three instalments.
Instalment 1 · The napkin sketch
Two pens, one manuscript.
We were writing a trilogy together. The writing came easily — the writing together did not. We lost each other's sentences, accidentally overwrote an afternoon's work, and waited on each other because only one of us could be in the file at a time. The manuscript lived in too many folders, with too many names, and no one knew which version was the real one anymore.
What we were missing wasn't another button. It was an agreement. One shared main text that stays sacred — the canon — that we build on together. And if one of us wants something different, you don't write it inside the other's text, but with a pencil: a proposal on a sheet beside it, waiting in the margin until the other chooses.
That evening it was on a napkin. The next morning we started building it — not to have it finished, but to be writing in it again by that afternoon.
Like to read the next instalment first? Join the waiting list →
Instalment 2 · The choices
Why silence, why local,
why Margo.
The best sentences rarely came at a desk with wifi. They came on the train, on the beach, in a rowing boat in the middle of a lake. So CollaDuet had to work there — without a connection, without intruding. Offline, for us, isn't an emergency mode; it's the default.
And it had to stay ours. Your words sit locally on your own machine, no account sneaking off to phone home, and you take everything with you whenever you want. What you write, we never hold hostage.
The hardest part was the help. We didn't want a writer writing along with us — we wanted to write ourselves. So we built Margo: a reader-along that runs on your own computer, knows your story, and warns you when your world contradicts itself, but never types a word for you. Her name comes from the Latin margo, the margin — where she lives. Too dumb to learn, smart enough to act.
Instalment 3 · The heart
You come back on purpose.
As we built, the heart of CollaDuet became a single sentence. You may write apart endlessly, and nothing gets lost — but on your return your work doesn't slip silently in somewhere. It arrives: marked in your colour, with one message for your co-author, and a walk spot by spot past everything that came together.
Because working on a book together means you want to see what the other did — and decide for yourself what to do with it: read, respond, or tick off. That's not a technical detail. That's why we write together.
Our trilogy isn't finished yet. CollaDuet grows with every scene we write in it. If this could be your way of writing together, then write along from the very start.
with each other, for each other
CollaDuet›Waiting list
Write along from the start
Put me on the waiting list.
No spam, no noise — one message when CollaDuet opens, and now and then an instalment of the story.
We use your address only for this and keep it until the release notice — or until you ask us to remove it. You can unsubscribe at any time, with one click or one email. Form not working? Email directly to wachtlijst@colladuet.nl.
The First Fifty
Founders.
The first fifty on the waiting list are our founders: they're the first to get access once the doors open, the first to help think about what we build — and whoever wants to is listed here by name. Just say so in your sign-up.
Names only with your consent — first name or pen name, and one email is enough to come off again.