File-manager integration

mdo's core convenience: open a .md file from your file manager and read it as rendered HTML immediately. Every integration launches the same mdo --open render-and-open path, so no .html file is ever left beside the source — output goes to a stable per-file temp path:

Windows  %TEMP%\mdo\<hash>\<name>.html
Linux    /tmp/mdo-<uid>/<hash>/<name>.html
macOS    $TMPDIR/mdo-<uid>/<hash>/<name>.html

The file-handler registration is per-user and reversible with mdo --uninstall-file-manager. (On Linux, the separate mdo Setup application-menu launcher and the installed binaries are untouched by that command; see the implementation details below.)

Windows Explorer

mdo.exe installs or removes its own per-user Explorer integration (no admin rights and no HKLM changes). Windows release ZIPs also include mdo-setup.exe, a double-clickable guided setup:

# Open the first-run setup (offers the optional Explorer integration install)
.\mdo-setup.exe

# CLI install: add an "Open as HTML" right-click verb and Open With app entry
.\mdo.exe --install-file-manager

# Undo everything the installer did
.\mdo.exe --uninstall-file-manager

Result after install:

• Right-click any .md file → Open as HTML. On Windows 11, this may appear under Show more options.
• Open with → Open as HTML appears as an available app for Markdown files.
• If you make Open as HTML the default handler, double-clicking a .md file opens the rendered page in your browser.

To make Open as HTML the default .md handler after installing, right-click a .md file → Open with → Choose another app → pick Open as HTML → tick Always use this app. Windows requires that last step to be done interactively.

Rerunning the installer is safe: it detects its own existing registration and keeps setup idempotent.

Windows implementation details

• The installer registers Open as HTML for .md files using per-user (HKCU) registry entries only.
• If mdo-open.exe is present next to mdo.exe, it is used as the Explorer handler to avoid the brief black console-window flash that Windows shows for normal console binaries. If only mdo.exe is present, the installer registers mdo.exe --open "%1" directly, so a single downloaded executable is enough.
• The Windows binaries embed the mdo icon; the installer also writes that icon to a per-user path and registers both mdo.exe and mdo-open.exe with the friendly app name Open as HTML, so Windows "Open with" surfaces never expose the wrapper binary name.
• mdo-setup.exe — and mdo-open.exe launched directly with no file — opens the guided setup in a fresh Windows Terminal (wt) window using the One Half Light color scheme, centered on the active display, falling back to a plain new console when wt cannot be started.

Linux file managers

mdo installs or removes its own per-user XDG integration; no companion install script is required:

# Open the first-run setup in a terminal (offers the optional integration install)
mdo-setup

# Add "Open as HTML" as an "Open With" handler for Markdown files
mdo --install-file-manager

# Same, but also make it the default Markdown handler
mdo --install-file-manager --set-default

# Undo everything the installer did
mdo --uninstall-file-manager

Result after install:

• Most XDG file managers (GNOME Files/Nautilus, and others): right-click a .md file → Open With → Open as HTML.
• With --set-default: double-clicking a Markdown file launches mdo --open.
• The rendered page opens in your default browser from the temp path above.

Linux implementation details

• The installer writes ~/.local/share/applications/mdo.desktop, whose command is the current binary plus --open %f, and a small Ⓜ SVG icon under ~/.local/share/icons/hicolor/scalable/apps/mdo.svg. The desktop entry is named Open as HTML, so file managers show an action-oriented entry instead of a tool-name-only entry.
• Rerunning the installer also removes older Nautilus Scripts entries named Preview with mdo or Render with mdo.
• The hosted Linux installer also writes the separate, visible ~/.local/share/applications/mdo-setup.desktop launcher (mdo Setup in application menus). It has no MIME types and remains installed if you run mdo --uninstall-file-manager; that command only removes the hidden Open as HTML file-handler integration.
• mdo-setup opens the first-run setup in a terminal window: your $TERMINAL, or a known terminal emulator (gnome-terminal, konsole, xterm, and others). If none is found it shows a zenity/kdialog/yad notice pointing you to mdo --setup. Running mdo-setup repairs its per-user application-menu entry if needed — useful after a Cargo or Homebrew install.
• Launching mdo-open directly with no file opens mdo-setup when the setup helper is present.

macOS Finder quick action

mdo does not ship a macOS installer yet, but Finder can run mdo --open through a per-user Automator Quick Action. Apple documents Quick Action workflows and shell-script actions in the Automator User Guide:

• Quick Action workflows
• Run Shell Script

Create a Quick Action in Automator, set it to receive files in Finder, add Run Shell Script, set Pass input to as arguments, and use the absolute path to mdo:

for file in "$@"; do
  /path/to/mdo --open "$file"
done

Save the workflow as Open as HTML. Finder then shows Quick Actions → Open as HTML for selected Markdown files, and running it opens the rendered page in your browser from the temp path above.