A small, fast window for Markdown files. Open a .md, read it nicely rendered, press Ctrl/⌘+E to edit it with a live preview, and save it as a PDF when you're done. Every file gets its own window.
mdown is not Electron and doesn't ship a browser. It is one native Rust program that uses the web view already on your computer (WebView2 on Windows, WKWebView on macOS), so the whole viewer is a single ~8 MB program.
cargo install mdownOr, to skip compiling, grab a prebuilt copy with cargo-binstall: cargo binstall mdown.
Building needs Rust 1.90 or newer. Either way you get two programs: mdown for the command line, and mdown-app, the window itself. Supported: Windows 10/11 (the WebView2 runtime ships with Windows 11 and current Windows 10) and macOS 11+.
mdown notes.md # open a file
mdown a.md b.md c.md # one window eachDrop .md files on a window to open them too. Links between Markdown files open in a new window (../ links included), links to folders, PDFs, images and text files open in their usual app, and links to anything else are shown in the file manager rather than run. Images and models resolve relative to the document, and the view updates by itself whenever the file changes on disk. If you have unsaved edits when that happens, mdown asks before replacing them.
cargo install can't ask you questions, so the first time you run mdown in a terminal it offers a one-time setup (and mdown install runs the same menu any time):
- Right-click menu only: adds "Open with mdown" for
.mdfiles. - Default app: double-clicking a
.mdfile opens it in mdown. - Both.
| Windows | macOS | |
|---|---|---|
| Right-click entry | Under Show more options on Windows 11 | Open With in Finder |
| Default app | Windows only lets you choose the default, so Settings opens: pick mdown for .md (and .markdown) once |
mdown asks macOS to make it the default; if macOS declines, use Get Info → Open with → mdown → Change All |
| What it touches | Per-user registry keys, no admin rights | A small ~/Applications/mdown.app it builds locally |
For scripts: mdown install --context-menu, --default or --all, with --yes to skip the question. mdown uninstall removes everything the setup added.
- Markdown: tables, task lists, footnotes, heading anchors, strikethrough, autolinks, front matter (hidden), and inline HTML (sanitized).
- Alerts: GitHub's
> [!NOTE],[!TIP],[!IMPORTANT],[!WARNING]and[!CAUTION]callouts. - Images: click one that's shown smaller than its real size to see it full size.
- Code: syntax highlighting for 28 common languages, loaded only when a document uses them.
- Math:
$inline$and$$display$$with KaTeX. - Diagrams:
```mermaidfences. - Charts:
```chartfences containing a Chart.js configuration as JSON. - 3D models:
shows an interactive viewer for.glb,.gltfand.stlfiles (drag to orbit, scroll to zoom).
A block that fails (bad Mermaid, broken JSON, a missing model) shows an inline error and the rest of the page renders normally. Each of the heavier features is loaded only when the document needs it, so plain Markdown stays quick. See docs/showcase.md for the document in the screenshots.
Ctrl/⌘+F finds text in the page (Enter and Shift+Enter step through the matches, Esc closes). Ctrl/⌘+Shift+O opens a Contents panel listing the headings, with the section you're reading highlighted; click one to jump to it.
Ctrl/⌘+E splits the window into an editor and a live preview (a CodeMirror editor with Markdown highlighting, undo history and search); press it again to go back to reading. The preview follows the editor line by line as you scroll, and clicking a heading in the Contents panel moves the editor there. Ctrl/⌘+S saves. Closing a window with unsaved edits asks first.
Ctrl/⌘+P opens the system print dialog, where Save as PDF is one of the printers. Printing always uses a clean light layout, with diagrams, charts and 3D models drawn as static images.
Right-click anywhere for copy and select-all (cut and paste in the editor), Copy link address and Copy code on links and code blocks, Find, edit/view mode, save, print, Contents, the theme, text size and page width settings, Show in File Explorer / Reveal in Finder, and Copy file path.
| Ctrl/⌘+F | Find (in the editor: the editor's search) |
| Ctrl/⌘+Shift+O | Show or hide the Contents panel |
| Ctrl/⌘+E | Toggle edit mode |
| Ctrl/⌘+S | Save |
| Ctrl/⌘+P | Print or save as PDF |
| Ctrl/⌘+Shift+L | Cycle the theme: system, light, dark |
| Ctrl/⌘ + + / - / 0 | Text size larger / smaller / actual (also Ctrl + mouse wheel or pinch) |
Theme, text size and page width are saved for all windows. Change them from the right-click menu, or edit settings.json:
| Platform | Location |
|---|---|
| Windows | %APPDATA%\mdown\settings.json |
| macOS | ~/Library/Application Support/mdown/settings.json |
{ "theme": "system", "width": "normal", "zoom": 1.0 }theme is system (follows the OS), light or dark; width is normal or wide; zoom runs from 0.5 to 3.0. mdown theme dark sets the theme from the terminal. Anything invalid falls back to the default.
- "mdown-app is missing next to this command": the two programs have to stay together. Reinstall with
cargo install mdown --force. - A blank window on Windows: install the WebView2 runtime.
- Windows doesn't offer mdown as the default: run
mdown install --defaultagain; the Default apps page lists apps registered by that command. - macOS after upgrading: run
mdown installonce more so~/Applications/mdown.appgets the new binary. - Remote images in a document load from the network like in any browser; local images are only served from inside the document's git repository (never from
.git), or from its own folder when it isn't in a repository.
The compiled front end is committed in dist/, so a normal build needs only Rust:
cargo build --releaseTo change the front end, edit frontend/src and run npm install && npm run build inside frontend/. node mkicon.mjs there regenerates the icons in assets/. cargo test runs the Rust tests.