Mac App Store · Coming Soon

Think in plain text. Ship in print.

DownSide is a native macOS markdown workspace built for people who live in .md files — instant preview, folder-native organization, and export that actually looks like a finished document. No accounts. No sync drama. Just your words on disk.

Buy now $39 one-time Direct download DownSide for Mac Download on the Mac App Store Coming soon Why plain text wins →

Platform: macOS 15+
Storage: Your files, your folders
Export: HTML · Print · PDF
By: AltaForma

Why DownSide

Built for writers who never stopped trusting plain text.

You don't need another database pretending to be a notebook. You need a Mac app that opens instantly, respects your folder structure, and makes markdown feel inevitable — from the first keystroke to the printed page.

⌁

Opens instantly

Open a folder, start typing. Live search across your vault. Autosave keeps up with your thinking. The UI stays out of the way until you need it.

◫

Live preview, real typography

Swiss Strict styling baked in — crisp headings, deliberate hierarchy, light and dark preview. Bring your own CSS when you want to go further.

⬡

Folder-native workflow

Your notes live where you put them — iCloud, Dropbox, a USB stick. DownSide doesn't lock you into a proprietary format or a hosted silo.

◎

Wiki links that work

Connect ideas with [[double-bracket links]] between files in the same workspace. Build a personal knowledge graph without leaving the editor.

⎔

Math, diagrams, code

KaTeX for equations, Mermaid for diagrams, Prism for syntax highlighting. Technical writing stays first-class, not bolted on.

↗

Export without ceremony

Standalone HTML, print preview with real page setup, multi-page PDF from your preview styles. What you see is what leaves your machine.

Keyboard-first Plain-text forever Research notes Technical docs Zettelkasten-curious Print-ready prose

The Philosophy

Files on disk beat databases in the cloud.

The best note systems feel invisible: a blinking cursor, a filename you chose, a preview that proves the words landed right. DownSide is Swift and SwiftUI on Apple silicon — WebKit for rendering, AppKit for the chrome that matters. No Electron. No subscription. No sync server to babysit.

Write in monospace. Preview in Swiss typography. Export when the document is ready to meet the world. That's the whole job.

0 Cloud accounts

100% Local files

∞ Your folders

# meeting-notes.md Quarterly planning Context 04 Three themes for Q3: focus, ship, polish. 05 Budget locked. Headcount flat. Decisions 07 - Launch DownSide beta in September 08 - Keep the editor native; no web client 09 - [[print-pipeline]] owns PDF quality bar Next 11 See [[roadmap]] for milestone dates.

The Interface

Editor on the left. Truth on the right.

A split workspace that feels like a proper Mac app — folder sidebar, monospace editor, live preview inspector, and a toolbar that respects your muscle memory.

Write & preview

Type markdown in a focused editor with syntax-aware highlighting. Preview updates as you write — scroll sync optional, distraction always off.

DownSide editor and live preview showing Diagrams.md with two rendered Mermaid diagrams

Folder workspace

Open any folder on your Mac. Browse, create, rename, and search files without leaving the window. Your vault structure stays yours.

DownSide three-pane workspace with sidebar search for code, Code Notes.md, and Print Pipeline at 720 words

Print & PDF

Real print preview with margins, page breaks, and Swiss typography tuned for paper. Export multi-page PDFs from the same render engine — no surprise layout shifts.

DownSide Print Preview for Print Pipeline with table of contents settings and roman page i

Your styles, your rules

Built-in Swiss Strict CSS for screen and print. Layer custom preview, syntax, and print stylesheets. Dark preview when you're burning the midnight oil.

DownSide Preferences Preview tab with Swiss Strict theme dropdown open

See it

The notes that show the product.

The Screenshot Vault is markdown, not PNGs. These five notes are the product examples: print ToC and page breaks, KaTeX, Mermaid, CriticMarkup, and a launch checklist. Download the folder and open it in DownSide.

Print Pipeline.md Print ToC marker, forced break, footnotes, export checklist

Print pipeline 09 Open Print Preview on this file. The marker 10 becomes a table of contents on paper. Screen is a draft of paper 15 Margins, running heads, and page numbers belong 16 to Document Setup — not to hope.  Checklist before you export 34 [x] Swiss Strict (or your CSS) on screen 35 [x] Same stylesheet in print 36 [ ] Page numbers via {page} / {pages} 37 [ ] Endnotes on, if you used footnotes

Equations.md KaTeX inline + display

Equations 12 Harmonic mean: $2ab / (a+b)$ e^{iπ} + 1 = 0 22 Taylor: f(x) = Σ fⁿ(a)/n! (x−a)ⁿ x = (−b ± √(b²−4ac)) / 2a

Diagrams.md Mermaid flowchart + sequence

```mermaid 12 flowchart LR 13 A[Start Here] --> B[Launch Brief] 14 A --> C[Print Pipeline] 15 A --> D[Equations] 16 B --> E[Literature Review] 17 C --> G[Colophon] ``` ```mermaid 24 You → Folder: write .md 25 Folder → Preview: live render 26 Preview → Paper: print / PDF ```

Revision.md CriticMarkup — show mode

Revision 09 We imported the vault into a hosted app 10 left the files where they were. 11 {~~BitWriter~>The Folder is the Book~~} 13 Print and preview must share an engine. 13 {>>Named in Launch Brief.<<}

Launch Brief.md Decisions checklist + milestone table

Launch brief 07 Ship when the preview matches the print output. Decisions 15 [x] Keep the editor native — no web client 16 [x] Plain-text files only 17 [ ] [[Print Pipeline]] owns the PDF bar Timeline 24 Beta notes vault · September · Editorial 25 Print styles locked · September

Download the example vault How these markers compile →

How It Works

Three steps. Zero ceremony.

From blank file to printed document without changing apps.

Open your folder

Point DownSide at the directory where your markdown already lives. Pick up exactly where you left off — no import wizard, no migration dance.

Write with preview

Compose in the editor, watch the preview prove your formatting, link between notes, drop in diagrams and math. Autosave handles the rest.

Ship it

Export HTML for the web, print from preview, or save a PDF that matches what you approved on screen. Your stylesheet goes with it.

$39. One time. Buy now.

Native Mac workspace — folder, split preview, print pipeline. No account, no subscription, no Tahoe requirement. Built by AltaForma.

Buy now $39 one-time Direct download DownSide for Mac Download on the Mac App Store Coming soon

Questions? hello@alta-forma.com