The classic writing app, with your AI inside it.

Proselon is a classic writing app with one key difference — an AI co-writer that works on your project alongside you. It can read anything on demand and draft directly onto the page. No more copy-pasting or running out of context. Works with your existing AI subscriptions, no API keys necessary.

Start 30 days freeAlready have an account? Download the app.
Proselon open to a manuscript of The Midnight Exchange, the book's acts and chapters listed in the file tree beside a scene in the editor, while the co-writer is asked to tell the writer about the story and answers by going and reading the book.
Plate 1. The Midnight Exchange, open to chapter one.

Do an afternoon of work with one instruction.

Unlike chat bots, the Proselon co-writer works directly on your project, reading and editing your story right alongside you. That means work that used to take an afternoon can take only one prompt.

Pick an instruction to see what the co-writer does with it.

Plate 2. One instruction, eleven passages changed.

It writes like you, not like a chatbot.

AI is much better at reproducing patterns than it is drafting from scratch, so the co-writer builds a record of passages written in your voice and uses that as the basis for everything it generates.

A chatbotThe Keeper’s Turn

In that moment, Nora couldn’t help but feel a profound sense of purpose wash over her. The lighthouse stood as a testament to her grandfather’s unwavering dedication, a beacon of hope that had guided countless souls home. For forty years he had tended its light, and now it was her turn to carry that torch forward. Little did she know, everything was about to change.

10 stock phrases112
The Keeper’s TurnProselon

Another person might have been driven mad long ago by the lighthouse beam, but not Nora. For her, the lighthouse was a welcome reminder. Her grandfather had kept its light for forty years. Now it was her turn to do the same.

113In your voice
Plate 3. One moment of a scene, written twice: by a chatbot with no example to follow, and by Proselon drafting against your voice corpus.

Continue or revise with one click.

You don't have to copy and paste or input a whole prompt just to continue a scene or revise a sentence. Simply select a passage and click to change or continue it.

Plate 4. A selection with the editor bar open.

Perfect attribution, down to the letter.

Readers, publishers, and platforms all care when and how much authors use AI in the writing process. Proselon keeps a record of where each character came from, whether typed by a human or generated by AI. When you get asked how much AI was used in your story, Proselon has an exact answer.

S1 - At the Board, Mid-Delivery

He laughed at me. The shock rose up in me unbidden, not a thing I went and fetched. The lamps along the top row went on blinking as they had all night, each one waiting its turn to be answered. I told him the truth, and he laughed at me.

1,530 words
Plate 5. Authorship for one scene, character by character. How Proselon attributes authorship

Powered by your favorite AI engine.

Most AI writing tools require an API key or a branded subscription. Proselon’s co-writer is powered using whatever AI you want, from frontier models to custom local ones to BYOK.

  • API keyAPI keyBilled per use
  • OllamaLM StudioLocal modelsFree · tool-calling
  • ChatGPTChatGPTAny plan
  • GeminiGeminiAI Pro or Ultra
  • GrokGrokPremium+ or SuperGrok
  • ClaudeClaudePro or Max

AI you can switch off.

AI can help with the writing process, but not all the time. When you want to turn it off, choose No AI under AI Engine in Settings. Proselon becomes a classic writing app, with no AI in sight.

YOUR WRITING ENGINE

Nothing you write goes to an AI, and Proselon starts no engine. Choose an engine above to turn the co-writer back on.

Plate 6. Settings, at AI Engine. Pick an engine and see what stays on.
  • The co-writerOff
  • Revise, Expand, Contract and ContinueOff
  • Your files and foldersOn
  • ThemesOn
  • Version historyOn
  • Your authorship recordOn

Themes you can read all day.

Nine beautiful themes to choose from. Choose a theme for everything you write, or give each project its own. Pick a theme you like, or a theme tailored to your platform.

ThemesChoose one

AO3, FanFiction.net, Wattpad, and Royal Road are trademarks of their respective owners. Proselon is not affiliated with or endorsed by them.

Plate 7. Every theme in the app, light and dark. Pick one to see it.

Markdown files, stored on your computer.

Your project's files are stored on your computer, one Markdown file per page. That's it. No database, no container, no proprietary format. Take your work and leave whenever you want.

The Midnight ExchangeManuscripts / Book 1 / Act I / Chapter 1COLUMN VIEW
Plate 8. The scene from Plate 1, as it sits on disk. Plain text document · 7 KB.
  • Saved by meBefore killing the subplotToday, 4:12 PM · 6 pages
  • AutomaticWhile writingToday, 3:42 PM · 3 pages
  • AutomaticBefore a Proselon updateYesterday, 9:04 AM · 12 pages
  • AutomaticWhile writingYesterday, 8:51 AM · 1 page
Plate 9. Four saves of The Midnight Exchange, one named before killing the subplot.

Every version kept, in a backup that goes anywhere.

Autosaves preserve your work, and any save can be read or brought back, one page or all of them, and is kept even if you restore from an older version. Backups are managed using git, a backup system used by developers, which means you can take your backups with you anywhere.

Decide what's included in context and what's not.

Lock or hide any page or folder. These statuses are in the code, not in a system prompt, meaning it's impossible for the AI to disobey them.

Plate 10. Locked: read, never altered. Hidden: never read at all.

Locked

A locked page or folder is read but never altered — by the co-writer or by your own editor — until you unlock it. Good for published chapters in serial novels, or published blog articles.

Hidden

A hidden page or folder is invisible to Proselon. The co-writer never reads it, no count includes it, no export carries it, and nothing in the story graph has it, though you still open it and write in it whenever you like.

Line-level citations.

Instead of copying a long section of text or having to describe where the AI should look, you can just cite the passage you are referring to. When the co-writer responds to you, it also cites its work, making it easy for you to find the passage it's referring to.

Plate 11. A citation, clicked, opening the scene at line 52.

Generate a story graph on demand.

Open the story graph, and the app reads your project and draws a web of the concepts within. There is no tagging chore and no metadata you have to update. Folders you create appear automatically in the legend.

Plate 12. The story graph for The Midnight Exchange.

Only six dollars a month.

One product, with everything included on both plans. The only decision is how often you are billed, and you make it after the trial rather than now. Your AI subscription is billed separately.

Monthly
$6a month

Billed monthly. Cancel any time, in one click.

Start 30 days free
Annual · Save $22 a year
$50a year

Two months on the house, or about $4.17 a month.

Start 30 days free
Both plans include
  • The AI co-writer, on all six engines
  • Continuity across a whole book or series
  • Automatic version history
  • Export to Word, EPUB, and more
  • Every theme, in a light half and a dark one
  • No credits or meters
30 days free, no card · we email before the trial ends · cancel in one click · refunds within 30 days of a chargeFull pricing details and billing questions

Your writing room is ready.

An AI co-writer that agentically reads your whole book, that runs on the AI subscriptions you already pay for. No API keys necessary.

Start 30 days freeAlready have an account? Download the app.