A Markdown browser/editor with built-in power and smile.
No plugins. No extensions. Everything you need — live preview, file browser, Git, website crawling, document import, AI agent integration — ships in a single 15 MB app. Open it and start writing.
Powered by Tauri v2, CodeMirror 6, and Cloudflare Workers AI.
| Feature | How it works |
|---|---|
| Fetch URL | Cloudflare Markdown for Agents — fast, free |
| Fetch URL (Render JS) | Browser Rendering — SPAs, dynamic sites |
| Crawl website | Browser Rendering /crawl API — crawl entire sites to Markdown files |
| Import documents | Workers AI AI.toMarkdown() — PDF, DOCX, XLSX, HTML, CSV, XML |
| Import images | Workers AI OCR — JPG, PNG, WebP, SVG |
| Paste / Drop images | Paste from clipboard or drag & drop — saves to ./assets/ with Markdown link |
| Batch import | Queue-based parallel conversion of multiple files via Worker |
| Drag & Drop | Drop any supported file onto the editor to import |
- Live preview — Split-pane with real-time rendering, DOM-diffing (idiomorph), and bidirectional scroll sync
- Multi-tab editing — Open multiple files in tabs, drag to reorder
- CodeMirror 6 — Syntax highlighting, line numbers, bracket matching, search & replace
- Command palette — Fuzzy search over all commands (Cmd+K); type
?to switch to semantic search - Formatting shortcuts — Bold, italic, strikethrough, inline code, link insertion
- Document cleanup — Normalize headings, tables, list markers, whitespace, CJK emphasis spacing in one click
- Markdown linting — 11 structural checks + CommonMark validation via comrak: heading hierarchy, broken links, table formatting, emphasis flanking, code blocks, footnotes, blank lines
- Code highlighting — 24 languages via highlight.js (lazy-loaded), copy button on hover
- KaTeX math — Inline
$...$and display$$...$$rendering - Mermaid diagrams — Flowcharts, sequence diagrams, etc. Click to open zoom/pan viewer with Copy as PNG
- GitHub-style alerts —
[!NOTE],[!TIP],[!WARNING],[!IMPORTANT],[!CAUTION]blockquotes with colored icons - Table of Contents — Heading navigation panel with active heading tracking (Cmd+4)
- Frontmatter panel — Collapsible YAML frontmatter display above the editor
- Table editor — Spreadsheet-like editing with Tab/Enter navigation, undo/redo, paste from TSV/CSV
- Presentation mode — Split document at
---and present slides fullscreen - Auto link title — Paste a URL to auto-fetch the page title and format as
[Title](url) - Smart typography — Auto-convert
...→…,--→–,---→—as you type - Note refactor — Extract selected text into a new linked Markdown file
- Semantic search — Natural language search across indexed documents via Vectorize (Cmd+5 or
?in command palette); crawled and imported files are auto-indexed - Multi-window — Open multiple windows with per-window state isolation and session restoration
- Auto-save & auto-reload — File-backed tabs auto-save; external changes detected and reloaded
- SVG inlining — Remote SVG images rendered inline with sanitization
- File tree sidebar — Browse, create, rename, duplicate, delete files and folders; drag & drop, search, file tagging
- Git panel — View changes, stage/unstage files, commit, push/pull with ahead/behind counts, fetch
- Clone repository — Clone Git repositories (HTTPS/SSH) and open them in the editor
- Copy Rich Text — Copy rendered HTML to clipboard (preview pane)
- Copy Markdown — Copy raw Markdown to clipboard (editor pane)
- Copy Mermaid as PNG — One-click PNG export from Mermaid diagrams (2x Retina)
- Copy code blocks — Hover any code block in the preview for a Copy button
- Publish to R2 — Share Markdown files via Cloudflare R2 with permanent or time-limited URLs
- MCP Server — AI agents (Claude Desktop, Claude Code, Cowork) can read/write editor content, manage files, browse projects, crawl websites, lint/normalize documents, and convert documents via Model Context Protocol (62 tools). See docs/ai-integration.md for setup.
- File-watcher sync — External edits by AI agents are automatically detected and reloaded in the editor
Press Cmd+K to open the command palette with all available commands. Right-click links in the preview for quick Fetch/Render/Crawl actions. See docs/keyboard-shortcuts.md for the full shortcut reference.
- macOS on Apple Silicon (M1/M2/M3/M4)
Homebrew (macOS):
brew install M-Igashi/tap/markupsidedownManual: Download the .dmg from the latest release, open it, and drag MarkUpsideDown.app to Applications.
Note: The app is not code-signed. For manual installs, run
xattr -cr /Applications/MarkUpsideDown.appor right-click → Open to bypass Gatekeeper. Homebrew handles this automatically.
The Worker powers document import and JS-rendered page fetching.
Automatic setup (recommended): On first launch, click Setup with Cloudflare in the Settings panel. This runs wrangler login, creates Cloudflare resources (KV, R2, Queue, Vectorize), deploys the Worker with a randomized URL, and configures secrets — all from within the app.
Manual setup: See docs/worker-deployment.md for step-by-step instructions.
On first launch, Settings opens automatically. If you used auto-setup, the Worker URL is already filled in. Otherwise, paste your Worker URL and click Test.
Create a symlink so you can open files from the terminal:
sudo ln -sf /Applications/MarkUpsideDown.app/Contents/MacOS/MarkUpsideDown /usr/local/bin/markupsidedownmarkupsidedown README.md # open a file
markupsidedown file1.md file2.md notes/todo.md # open multiple files as tabsIf the app is already running, files are opened in the existing window. See docs/cli.md for details.
Requirements: Rust 1.85+, Node.js 22+, Vite+ (optional, for lint/format)
cd ui && npm install && cd ..
cargo tauri dev # dev mode with hot-reload
cargo tauri build # production build| Document | Contents |
|---|---|
| docs/ai-integration.md | AI agent setup guide (quick start) |
| docs/mcp-server.md | MCP server reference (62 tools, standalone mode) |
| docs/worker-deployment.md | Worker deployment, API tokens, pricing |
| docs/architecture.md | Data flow, components, IPC/bridge API reference |
| docs/keyboard-shortcuts.md | All keyboard shortcuts |
| docs/cli.md | CLI setup and usage |
AGPL-3.0-or-later. See LICENSE for details.
For commercial licensing inquiries, please contact the author.