markmedown

A zero-build, single-page Markdown editor with live preview. Open index.html in a browser — that's the whole install.

Try it live →

Features

• Real code editor — CodeMirror with line numbers, Markdown syntax highlighting, and search/replace (Ctrl+F find, Shift+Ctrl+F replace)
• Live preview — GitHub-flavored Markdown rendered as you type (marked + DOMPurify)
• Mermaid diagrams — fenced ```mermaid blocks render inline
• Math — $inline$ and $$block$$ LaTeX via KaTeX (plain $5 and $10 stays text)
• YAML front matter — a leading --- block is treated as metadata and hidden from the preview
• Syntax highlighting — fenced code blocks via highlight.js
• Formatting toolbar — headings, bold/italic/strikethrough, links, images, code, quotes, lists, tasks, tables, rules (all toggleable)
• Keyboard shortcuts — Ctrl+B bold, Ctrl+I italic, Ctrl+K link, Ctrl+S save, Ctrl+O open, Tab/Shift+Tab indent; full undo/redo history across toolbar actions
• Smart lists — Enter continues bullet/numbered/task lists, Enter on an empty item ends the list
• Paste & drop images — paste from clipboard or drop an image file to embed it inline; drop a .md file to open it
• File open/save — load .md files, download under the opened filename
• Export — styled standalone HTML file (needs internet for code/math CSS), or Print for PDF via the browser
• Autosave — draft persists in localStorage across reloads
• Synced scrolling between editor and preview
• Dark mode — follows your system preference
• Word/character count and cursor position in the status bar

Contributing

Contributions welcome — see CONTRIBUTING.md. The short version: keep it zero-build, pin CDN dependencies with SRI, and sanitize everything that reaches the preview.

License

MIT