A minimal, native macOS app that opens .md files on double-click and renders them GitHub-style — with proper light and dark mode. It also ships a Quick Look extension, so hitting the space bar on a .md file in Finder shows the rendered preview instantly.
Double-click a Markdown file → read it rendered. That's the whole app.
I'm working with AI tools all day, and they produce .md files constantly — plans, notes, specs, READMEs, agent output. On macOS there's no good built-in way to just read one: double-clicking opens a code editor showing raw # and *, and the heavier Markdown apps want you to manage a library, sign in, or sync to a cloud.
I just wanted the dead-simple thing: double-click a .md file and see it rendered nicely, the way GitHub shows it. No accounts, no library, no clutter. So I built it.
Grab the latest .app from the Releases page, unzip it, and drag MarkdownViewer.app into /Applications.
The app is ad-hoc signed (not notarized), so the first time you open it macOS may warn that it's from an unidentified developer. Right-click the app → Open, then confirm — you only have to do this once.
Requires macOS 13 (Ventura) or later.
Open the app's Settings (⌘,) and click "Use Markdown Viewer for Markdown Files". From then on, every .md file opens here on double-click, and the space-bar Quick Look preview works in Finder too.
- 📄 Double-click to read — opens
.md,.markdown,.mdown,.mkdn, and.mkdfiles - 🎨 GitHub-style rendering — clean typography, code blocks, tables, the works
- 🌗 Light & dark mode — follows your system appearance automatically
- 👀 Quick Look preview — press space on a Markdown file in Finder
- 🔗 Links open in your browser — no surprise in-app navigation
- 🪶 Tiny & native — pure SwiftUI + WebKit, no Electron, no telemetry, no accounts
Requires the full Xcode toolchain (the Command Line Tools alone can't build SwiftUI):
./build-app.shThis produces dist/MarkdownViewer.app, ad-hoc signs it, and registers it with Launch Services. Move it to /Applications if you like.
Sources/MarkdownViewerCore— Markdown → styled HTML page (tested; uses Ink)Sources/MarkdownViewer— SwiftUI document app showing the HTML in aWKWebViewSources/QuickLookPreview— Quick Look extension rendering the same HTML for Finder's space-bar previewResources/Info.plist— declares the Markdown document type so Finder offers the app
DEVELOPER_DIR=/Applications/Xcode.app/Contents/Developer swift testMIT