Markdown Viewer

A lightweight, instant markdown file viewer that runs as a Progressive Web App. Install it from your browser and set it as your default .md file handler — double-click any markdown file and it just works.

Install

1. Open spskelly.github.io/markdown-viewer
2. Install — click the install icon in the address bar (or browser menu → "Install Markdown Viewer")
3. Set as default — right-click any .md file → "Open with" → "Markdown Viewer" → "Always use this app"

That's it. Now double-clicking any .md file opens it beautifully.

Requires a Chromium browser (Chrome, Edge, Brave) for the file handler feature. Firefox and Safari can use the app but won't register as a file handler.

Features

• File handler — registers as a default app for .md files on your system
• Offline — works without internet after install
• Dark/Light mode — toggle with Ctrl+D (preference saved)
• Syntax highlighting — 100+ languages via highlight.js
• Mermaid diagrams — flowcharts, sequence diagrams, Gantt charts, and more
• Drag & drop — drop files directly onto the window
• Keyboard shortcuts — press ? for the full list
• Print-friendly — clean print stylesheet

Why?

There's no lightweight, dedicated markdown viewer. Everything is either a heavy editor (VS Code, Typora), a clunky browser extension, or a terminal tool. This fills that gap: double-click → instant rendering.

Development

Want to modify it? Clone the repo and serve over HTTPS (or localhost). The codebase is five files:

• index.html — app shell
• app.js — file handling, rendering, UI
• styles.css — GitHub-style markdown CSS
• manifest.json — PWA config
• service-worker.js — offline caching

License

MIT