In the age of AI, Markdown should be simple enough.

As a Vibe Coding developer obsessed with Prompts, Agents, and Skills, I’ve used too many Markdown tools: some are too heavy, some charge subscriptions, and some sync your content to the cloud without asking. I just wanted to open a browser, type, see the layout, and take it away.

So I built this editor.

It is just one HTML file. Double-click to write. Everything is stored locally, and it works offline. It supports nearly all mainstream Agents — Codex, Claude Code, Openclaw, and more. Whether you’re designing an AGENTS.md or a Skill.md, you can do it here.

If you also believe that in the age of AI, Markdown is the first language — welcome to use it, fork it, and star it.

• Single-file markdown-editor.html: double-click to run in the browser.
• All core styles, structure, and logic are inlined; works offline.

• Drag-and-drop import: drop files directly into the window.
• Live preview: write on the left, preview on the right in real time.
• Multiple layouts: edit + preview, edit only, or preview only.
• Source mode: edit raw Markdown directly on the right side.
• Draggable split: adjust the editor/preview ratio; position is remembered.

Powered by i18n.js: Simplified Chinese, Traditional Chinese, English, Japanese, Korean, Spanish, French, German, Russian, Portuguese.

Language preference is persisted to localStorage.

• One-click theme switching with automatic persistence.
• All colors use CSS variables, making customization easy.

• Auto-saves content to browser localStorage every 500ms.
• Content, filename, split ratio, collapsed states, theme, and language all survive page refresh.

• Pure native frontend: HTML5 + CSS3 + Vanilla JavaScript, no framework.
• Markdown rendering: marked.js
• Math: KaTeX ($...$ inline, $$...$$ block)
• Diagrams: Mermaid 10 (mind maps and flowcharts)
• Image export: dom-to-image-more
• Local proxy: Python 3 + http.server (optional, for webpage-to-Markdown)

┌─────────────────────────────────────────────────────────────┐
│                    markdown-editor.html                      │
│  ┌──────────────┐         ┌──────────────┐                  │
│  │  Editor      │  sync   │  Preview     │                  │
│  │  (textarea)  │ ──────▶ │  (marked.js) │                  │
│  └──────────────┘         └──────────────┘                  │
│         │                         │                         │
│         ▼                         ▼                         │
│   localStorage               KaTeX / Mermaid               │
│         │                         │                         │
│         ▼                         ▼                         │
│   auto-save / state restore  formula / diagram render      │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
                   web-to-md-proxy.py (optional)
                    web fetching + anti-bot bypass

.
├── markdown-editor.html    # Main editor (single-file app)
├── i18n.js                 # i18n dictionary (10 languages)
├── web-to-md-proxy.py      # Optional local proxy script
├── public/                 # Static assets
│   ├── 关于作者.md
│   ├── 产品海报.png
│   └── 产品界面.png
└── README.md               # This file

# Clone the repo
git clone https://github.com/woyin2024/lengyi-markdown-editor.git

# Double-click to open
markdown-editor.html

cd markdown-editor

# Python 3
python -m http.server 8080

# Or Node.js
npx serve .

# Open in browser
open http://localhost:8080/markdown-editor.html

# Install requests (optional, recommended)
pip install requests

# Start the proxy
python web-to-md-proxy.py

# Default port 8765
# Check "Use local proxy" in the editor

This project started from my own need for a simple writing tool, but I believe it can be better.

New features, bug fixes, UI improvements, language additions, and documentation improvements are all welcome:

1. Fork the repository
2. Create your feature branch: git checkout -b feature/AmazingFeature
3. Commit your changes: git commit -m 'Add some AmazingFeature'
4. Push to the branch: git push origin feature/AmazingFeature
5. Open a Pull Request

This project is licensed under the MIT License.

You are free to use, modify, and distribute. For commercial use, please obtain authorization. I only hope that one quiet afternoon, when you write something you are truly satisfied with, you might remember where this little tool began.

Leng Yi (冷逸), founder of Chinese top AI media "沃垠AI", a Vibe Coding developer who can’t really code but loves to dive deep into Prompts, Skills, and Agents.

• Unified account across platforms: 沃垠AI
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