MarkUpsideDown

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.

Features

Markup to Markdown

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

Editor

• 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 Browser & Git

• 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
• GitHub issues & PRs — Browse issues and pull requests of the project's GitHub remote, then edit a title and body as Markdown and push it back (requires the gh CLI)
• Clone repository — Clone Git repositories (HTTPS/SSH) and open them in the editor

Clipboard & Copy

• 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

Publishing

• Publish to R2 — Share Markdown files via Cloudflare R2 with permanent or time-limited URLs. Optional R2 public access keeps the Worker URL secret

AI Agent Integration

• 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 (66 tools). See docs/ai-integration.md for setup.
• File-watcher sync — External edits by AI agents are automatically detected and reloaded in the editor

Keyboard Shortcuts

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.

Requirements

• macOS on Apple Silicon (M1/M2/M3/M4)

Getting Started

1. Install the App

Homebrew (macOS):

brew install M-Igashi/tap/markupsidedown

Manual: Download the .dmg from the latest release, open it, and drag MarkUpsideDown.app to Applications. The app is signed and notarized by Apple, so it opens without Gatekeeper warnings.

2. Set Up the Cloudflare Worker

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.

3. Configure the App

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.

4. CLI Access (Optional)

Create a symlink so you can open files from the terminal:

sudo ln -sf /Applications/MarkUpsideDown.app/Contents/MacOS/MarkUpsideDown /usr/local/bin/markupsidedown

markupsidedown README.md                          # open a file
markupsidedown file1.md file2.md notes/todo.md    # open multiple files as tabs

If the app is already running, files are opened in the existing window. See docs/cli.md for details.

Build from Source

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

Documentation

Document	Contents
docs/ai-integration.md	AI agent setup guide (quick start)
docs/mcp-server.md	MCP server reference (66 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

License

AGPL-3.0-or-later. See LICENSE for details.

For commercial licensing inquiries, please contact the author.