mdediter

A lightweight Markdown viewer and editor, available as a Windows desktop app (Go + Wails + Svelte) and as a browser app from the same codebase.

Try it online: mdediter.mooma.style — no install required.

Features

• Live preview — editor on the left, rendered preview on the right
• View modes — Edit only / Split / Preview only (toggle with Ctrl+/)
• Scroll sync — bidirectional, overall-ratio based
• GitHub Flavored Markdown — tables, task lists, strikethrough
• KaTeX math — inline $...$ and block $$...$$
• Syntax highlighting — both in the editor (CodeMirror) and preview (highlight.js)
• Tabs — open multiple files at once
• Drag & drop — drop .md files onto the window
• CLI arguments — mdediter.exe a.md b.md opens files at startup
• Recent files — last 10 files remembered
• Atomic save — temp-file + rename to prevent corruption on crash
• Single-exe distribution — no installer required

Web version

Open mdediter.mooma.style in any modern browser — nothing to install. It shares the editor, preview, tabs, GFM, KaTeX and search with the desktop app. File handling differs by platform: the web version opens files via a file picker, saves by downloading the file, and supports drag & drop of .md files. A link to download the Windows desktop app is shown in the toolbar.

Installation (Windows desktop)

Download the latest zip from mooma.style/app or Releases, unzip, and run mdediter.exe.

Windows SmartScreen warning: the binary is unsigned, so on first launch you may see "Windows protected your PC". Click More info → Run anyway. This is expected for any unsigned Windows app.

System requirements

• Windows 10 (1803+) or Windows 11
• Microsoft Edge WebView2 Runtime (pre-installed on Win11; auto-updated on Win10)

Opening files

• Double-click the exe to launch with a Welcome tab
• Drag & drop .md files onto the window
• Command line — pass file paths as arguments:

  mdediter.exe README.md docs\spec.md
  

  Each path becomes a tab. Relative paths are resolved against the current directory.
• File association — associate .md with mdediter.exe in Windows to open by double-clicking files

Keyboard shortcuts

Key	Action
Ctrl+O	Open file
Ctrl+S	Save
Ctrl+Shift+S	Save As
Ctrl+N	New tab
Ctrl+W	Close tab
Ctrl+/	Cycle view mode
Ctrl+F	Search
Ctrl+H	Replace
Ctrl+Z / Ctrl+Y	Undo / Redo
Right-click	Context menu (Cut / Copy / Paste)

Tech stack

• Backend: Go 1.23+ with Wails v2
• Frontend: Svelte 3 + TypeScript + Vite 3
• Editor: CodeMirror 6
• Markdown: markdown-it + GFM + task-lists + KaTeX
• Syntax highlighting: highlight.js

Building from source

Prerequisites

• Windows 10/11
• Go 1.23+
• Node.js 18+
• Wails CLI v2

go install github.com/wailsapp/wails/v2/cmd/wails@latest
wails doctor    # verify environment

Build

wails build -platform windows/amd64

Output: build/bin/mdediter.exe

Build the web version

The frontend is a plain Vite app, so the browser build needs no Go/Wails:

cd frontend
npm install
npm run build      # → frontend/dist/ (static SPA)

Platform differences (native file dialogs vs. file picker + download) are handled at runtime in frontend/src/lib/platform.ts, which detects the Wails runtime (window.go) and falls back to browser APIs otherwise.

Dev mode

wails dev

Hot-reload is enabled for frontend changes.

License

MIT — see LICENSE.