Markdown previews are usually cluttered, browser-based, or tied to editors.
MDviewer is a tiny native macOS app that opens any Markdown file as a clean, print-ready document.
Most Markdown previews are inside editors or browsers.
MDviewer is different:
- Double-click a Markdown file and read it immediately
- Clean typography optimized for printing
- No Electron, no runtime dependencies
- Fully local and secure
- Native macOS — Cocoa + WKWebView, launches instantly, under 1 MB
- Print-ready typography — serif body, clean headings, proper spacing
- PDF export —
Cmd+Shift+Eto save,Cmd+Pto print - In-document search —
Cmd+Ffinds text in the rendered Markdown, with next/previous match navigation - Live reload — re-renders automatically when the file changes on disk
- GitHub Flavored Markdown — tables, task lists, fenced code blocks
- Mermaid diagrams — renders fenced
mermaiddiagrams inline, fully local - LaTeX math — renders inline
$...$and block$$...$$math with bundled KaTeX - Dark mode — the app and Quick Look previews follow your macOS appearance setting, including Mermaid diagrams (rendered and cached in both themes)
- Secure — HTML sanitized with DOMPurify, strict Content Security Policy
- Finder integration — registers as default
.mdhandler; double-click to open - Quick Look — press Space on a Markdown file in Finder for a fully rendered preview: tables, code, task lists, images, LaTeX math, and Mermaid diagrams (from the app's render cache — or live everywhere with the optional
--with-mermaid-helperinstall flag) - Font settings — pick the document font in Settings (
Cmd+,): Serif (default), GitHub, or Geist (the Next.js font, bundled) - Tabbed windows — multiple documents in one window
- Local-first — no telemetry, no accounts, and no network calls except the update check you trigger yourself from the menu
- Grab
Markdown-Viewer-macOS.zipfrom Releases - Unzip, drag to
/Applications - On first launch, macOS will block the app because it's unsigned. To open it:
- Right-click (or Control-click) the app → click Open → click Open again in the dialog
- Or run in Terminal:
xattr -cr /Applications/Markdown\ Viewer.app
- After the first open, it launches normally like any other app
git clone https://github.com/JackYoung27/mdviewer.git
cd mdviewer
./build.sh # builds to dist/Markdown Viewer.app
./build.sh installer # builds dist/Markdown-Viewer-Installer.pkg — a standard
# macOS installer with checkboxes for "default .md viewer"
# and the optional Mermaid Quick Look helper
./install.sh # CLI alternative: copies to /Applications and sets as
# default handler; add --with-mermaid-helper for live
# Mermaid in Quick LookDesigned to be inspectable and minimal:
- The app makes no network requests on its own — "Check for Updates…" in the menu is the only network call, and only when you click it.
- The Quick Look extension is sandboxed with read-only filesystem access (so previews can load images your markdown references — wherever the file lives — and the diagram cache). It cannot write anything. macOS additionally asks once before it can read images in privacy-protected folders like Desktop or Documents.
- No background processes by default. The optional Mermaid helper (only if you install with
--with-mermaid-helper) appears under Login Items as a background item; launchd spawns it on demand and it exits after 45 seconds idle. Remove it anytime:launchctl bootout gui/$(id -u)/com.local.markdown-viewer.render-helper && rm ~/Library/LaunchAgents/com.local.markdown-viewer.render-helper.plist - All vendored libraries (marked, DOMPurify, Mermaid, KaTeX, Geist) are downloaded from npm at build time and verified against pinned SHA-256 hashes.
Requires Xcode Command Line Tools (xcode-select --install).
| Action | Shortcut |
|---|---|
| Open file | Cmd+O |
| Settings | Cmd+, |
| Find in document | Cmd+F |
| Next match | Cmd+G |
| Previous match | Cmd+Shift+G |
| Reload | Cmd+R |
Cmd+P |
|
| Export PDF | Cmd+Shift+E |
| Close window | Cmd+W |
| Document view | Code blocks | Checklists |
|---|---|---|
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