/pro-SAY-don/ · /pro-SY-din/

Ver. 0.9.6✦Thursday, June 18, 2026✦Price: Free

The compleat writing app.
Plan, write, finish. Like the gods.

Free
Offline
Your files
No forced signup
No AI

Infinite story boardFull fledged WikiDistraction-free editorInstant idea captureSmart searchEasy manuscript compileAutomatic versionsPlain Markdown filesOffline-firstNever forced to sign upNo AIYou own your filesInfinite story boardFull fledged WikiDistraction-free editorInstant idea captureSmart searchEasy manuscript compileAutomatic versionsPlain Markdown filesOffline-firstNever forced to sign upNo AIYou own your files

The Board

Infinite Planning Board.

Plan branching ideas, build reference boards, and map your whole story on a beautiful canvas. It can handle hundreds of images easily.

A Proseidon board mid-brainstorm: scenes, characters and notes connected in plain language. — **Fig. 1 —** A board mid-brainstorm — scenes, characters and notes in plain language.

A full Proseidon board: a whole story mapped out on one canvas. — **Fig. 1 —** A board mid-brainstorm — scenes, characters and notes in plain language.

The Editor

A clean, fast page.

Distraction-free, and quick even at a million words. Customize it however you like.

The Proseidon editor — a full page of prose in clean Markdown. — Fig. 2 — A clean page that reads like a book as you type. More about the editor →

Capture & Find

Never lose a thought.

01 Catch it

Quick capture

Have a random thought in the middle of something? Capture and save it with a single shortcut.

02 Find it

Smart search

Ideas you save won't get lost. Smart Search helps you find by any keyword.

The search bar — results by name and full text as you type.

The Wiki

Build your world.

Every character, place and thing gets its own page. Connect them and you've got a full wiki for your story.

entityn.

A single page for anything in your world — character, place, item. Typed fields for the facts, prose for the rest, an image if you have one.

Connect them with plain-text links and the wiki builds itself.

See the wiki →

A character page — a typed infobox beside a Markdown bio. — **Fig. 3a —** a character’s page: a typed infobox for facts, prose below.

Proseidon with a location page — Hogwarts — open in the full app. — **Fig. 3b —** places get a page too, here inside the full app.

A list of the characters in the wiki. — **Fig. 3c —** your own kinds of thing, listed however you like.

Versions

Nothing is ever lost.

Proseidon auto-saves a version every time you make changes — and you can name your own snapshots too. Step back to any draft, anytime. It all lives in your own folder.

No backups to set up. Nothing to lose. Just write.

A file's version history — auto-saves and named snapshots, each ready to restore. — A file’s history — auto-saves and named snapshots, ready to restore.

Also in this issue

A few more things you’ll reach for.

Writing stats

Hit your targets.

Track your goals, daily targets and streaks across today, this week and the whole manuscript.

The writing-stats overview — today’s words, the week, pace and the manuscript goal.

Streaks

Keep the chain going.

A whole year of writing shown as a heatmap — one square for each day.

Sprint timer

Heads down.

Set a timer and write against the clock.

Media

Play it right there.

Images, video and PDFs sit beside your words — and the built-in player runs your music playlists while you write.

Theming

Make it feel like yours.

Theme the whole workspace — colors and the overall look.

Compile

Bind it into a book.

Line up your scenes and Proseidon sets them as one manuscript — chapter headings, title page, real book type. Export to PDF, DOCX or Markdown.

A compiled chapter — a designed heading, set like a printed book.

A letter from the desk

It’s just me — and here’s the deal.

Dear reader,

Why did I build Proseidon? I was uneasy with the way software and the internet are going. There are plenty of lovely writing tools out there, but most are online, or backed by some kind of corporate, profit-driven motive. I want this one to be driven by something else — my love of writing. I didn’t want my writing, whatever its quality, sitting on someone else’s cloud, feeding their AI models. So I made the opposite of that.

Everything you write in Proseidon is just plain files, sitting on your own computer. No account is required, and it just works. It’s like MS Office back in the day, before subscriptions — except it’s free, and it does far more than put words on a page. If Proseidon vanished tomorrow, every word would still be yours, on your own device. That shouldn’t be a radical idea in software — but sadly, today, it is.

Proseidon will never add generative AI features. Your words stay on your device — every one of them yours.

Every feature in Proseidon is me going "that’s cool — I want that" or features I wish existed. No paywall, no multiple apps to manage one project. More awesome stuff is coming — it’ll just take me some time. A few optional online touches are on the way too: connecting your own drives if you want them, and a hub where writers can share work and trade feedback. Optional always means optional.

If you’d like to help, the best things are simple — use it, tell me what’s broken, and get your writer friends to use it. If there’s a feature you want, or you just want to say hi, I’m on Discord and email: deep@proseidon.io, and I read everything. And if you ever want to go further than that, there’s a Patreon.

Thank you for trusting me with your writing. I don’t take it lightly.

— DeepDesign, the guy making Proseidon

A Proseidon project's file tree — manuscript, planning, story bible and media, all plain files in one folder. — **Fig. 5 —** Your whole book — plain files, in a folder you own.

Proseidon — the offline-first writing app to plan, write and finish your book