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Markdown Viewer Wiki: Online Markdown Editor, Live Preview, Diagrams, and Export

Welcome to the documentation for Markdown Viewer. Markdown Viewer is a browser-based Markdown editor, viewer, reader, and previewer for opening .md and .markdown files, writing plain Markdown, and reading a split-screen live Markdown preview with sync scrolling. It includes document tabs, GitHub-Flavored Markdown, comments and suggestions, rich visual renderers, Markdown-to-PDF/HTML/PNG exports, Share Snapshot links, Live Share rooms, a PWA-capable web build, Docker deployment, and a lightweight Neutralinojs desktop build.

Most editing and rendering happens on your own device. The important exceptions are documented clearly: GitHub import contacts GitHub, remote diagram fallbacks contact third-party renderers, large Share Snapshot links use temporary Cloudflare KV storage, and Live Share relays temporary collaboration updates through Cloudflare Durable Objects. The web deployment also applies CSP and security headers, while the desktop build uses a restricted native API allowlist.

Start Here

Need	Page
Learn every feature, limitation, and data-handling detail	Features
Use the editor day to day	Usage Guide
Add and manage comments or suggestions	Usage Guide: Comments and Suggestions
Write supported Markdown, math, diagrams, maps, STL, and ABC notation	Markdown Reference
Install locally, in Docker, or as a desktop app	Installation
Tune deployment and runtime settings	Configuration
Deploy with Docker and reverse proxies	Docker Deployment
Build and understand the Neutralino desktop app	Desktop App
Understand Live Share on Cloudflare	Live Share Cloudflare
Add or maintain interface languages	Localization
Review project history and design decisions	Development Journey
Answer common privacy and troubleshooting questions	FAQ
Contribute changes	Contributing

Quick Run Options

Method	Command	URL
Python static server	python -m http.server 8080	http://localhost:8080
Node static server	npx serve . -p 8080	http://localhost:8080
Docker Compose	docker compose up -d	http://localhost:8080
Docker image	docker run -d --name markdown-viewer -p 8080:80 ghcr.io/thisis-developer/markdown-viewer:sha-15eafb0	http://localhost:8080
Desktop app	Download from GitHub Releases or build from desktop-app/	Desktop window

Run local web builds through localhost or another HTTP(S) server. Opening index.html with file:// can break Web Workers and Service Workers because browsers block those APIs from local files.

Product Principles

Principle	What It Means
On-device editing	Normal typing, preview, tabs, exports, themes, and settings stay on the user's device. No login is required.
Explicit network features	Any feature that sends content elsewhere is user-triggered or tied to a renderer/importer that is documented.
Rich Markdown support	The live preview supports GFM tables/task lists, math, footnotes, alerts, Mermaid, PlantUML, Graphviz, D2, Vega-Lite, Markmap, WaveDrom, maps, STL, ABC notation, and more.
Responsive performance	Large documents use debounced rendering, optional worker rendering, DOM patching, and cached measurements.
Deploy anywhere	The app can run as static files, a PWA, a Docker container, or a lightweight Neutralinojs desktop build.

Privacy At A Glance

• No accounts, cookies, analytics, ads, or telemetry are implemented.
• Normal documents and settings are stored in browser localStorage or local desktop storage.
• Comments and suggestions stay with normal local tabs, are excluded from exports and Share Snapshot, and synchronize only during an active Live Share room.
• Private mode clears document state and prevents normal document-state persistence until it is turned off; the About dialog also provides Clear local data.
• Small Share Snapshot links keep compressed content in the URL hash.
• Large Share Snapshot links upload the snapshot to Cloudflare KV for up to 90 days and remain bearer links for anyone who has the URL.
• Live Share sends real-time updates, display names, cursors, and presence through a Cloudflare Durable Object while the room is active.
• Live Share host, edit, and view capabilities are authenticated server-side, and unsupported WebSocket origins are rejected.
• Remote diagram renderers receive diagram source when PlantUML, D2, Graphviz, Vega-Lite, WaveDrom, or some preview helpers need them.

For the complete table of data flows, see Features.