MarkView

A native macOS markdown preview app built with Swift and SwiftUI. No Electron, no web server — just a fast, lightweight previewer that renders GitHub Flavored Markdown.

Demo

Screenshots

Preview only	Editor + Preview

Features

• Live preview with split-pane editor and WKWebView rendering
• GitHub Flavored Markdown via Apple's swift-cmark (tables, strikethrough, autolinks, task lists)
• Syntax highlighting for 18 languages via Prism.js
• Markdown linting with 9 built-in rules and status bar diagnostics
• File watching with DispatchSource (works with VS Code, Vim, and other editors)
• Multi-format support via plugin architecture (Markdown, CSV, HTML)
• HTML sanitizer that strips scripts, event handlers, and XSS vectors
• Mermaid diagrams — flowcharts, sequence, Gantt, ER, and pie charts via mermaid.js
• Bidirectional scroll sync — frame-perfect editor/preview sync via CADisplayLink
• Local image rendering — correctly inlines relative paths like ![](./image.png)
• Drag and drop — drop any .md file onto the window to open
• Find & Replace — Cmd+F to find, Cmd+Option+F to find and replace
• Format on save — auto-applies markdown lint fixes when saving
• Auto-save — configurable interval saves edits without manual Cmd+S
• Word count — live word and character count in the status bar
• Scroll position preservation — reopening a file restores your last scroll position
• Configurable tab size — set 2, 4, or 8 spaces per tab in settings
• Line numbers — toggle line numbers in the editor pane
• Window auto-resize — smart resize when toggling editor/preview panes
• Export to HTML and PDF
• Dark mode support with system/light/dark theme options
• 18 configurable settings including font, preview width, tab behavior, and more

Installation

Homebrew (recommended)

# Full .app with Quick Look extension
brew install --cask paulhkang94/markview/markview

# CLI only (builds from source)
brew tap paulhkang94/markview
brew install markview

The app is Apple notarized and Gatekeeper approved — no quarantine warnings on install.

Build from source

Prerequisites: macOS 14+, Swift 6.0+ (included with Xcode Command Line Tools)

git clone https://github.com/paulhkang94/markview.git
cd markview
swift build -c release

Install as app (Open With support)

bash scripts/bundle.sh --install

This creates MarkView.app in /Applications and registers it with Launch Services. You can then right-click any .md file in Finder and choose Open With > MarkView.

Install CLI commands

bash scripts/install-cli.sh

This creates mdpreview and md symlinks in ~/.local/bin/. Note: if md is aliased in your shell (e.g., to mkdir), use mdpreview instead.

Usage

CLI

mdpreview README.md       # Open a file
mdpreview                 # Open empty editor

Finder

Right-click any .md, .markdown, .mdown, .mkd file > Open With > MarkView

Programmatic

open -a MarkView README.md

MCP Server (AI Integration)

MarkView includes an MCP server that lets AI assistants preview markdown directly in MarkView.

Tools

Tool	Description
preview_markdown	Write content to a temp file and open it in MarkView with live reload
open_file	Open an existing .md file in MarkView

Quick Start (npx)

npx mcp-server-markview

Claude Code Setup

The easiest way — run this once in your terminal:

claude mcp add --transport stdio --scope user markview -- npx mcp-server-markview

This adds MarkView to ~/.claude.json (user scope — available in all projects).

Or add it manually to ~/.claude.json:

{
  "mcpServers": {
    "markview": {
      "command": "npx",
      "args": ["mcp-server-markview"]
    }
  }
}

Note: MCP servers belong in ~/.claude.json, not ~/.claude/settings.json. The settings file is for permissions only.

Claude Desktop Setup

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "markview": {
      "command": "npx",
      "args": ["mcp-server-markview"]
    }
  }
}

Test the MCP server

bash scripts/test-mcp.sh

Architecture

Sources/MarkViewCore/           # Library (no UI, fully testable)
  MarkdownRenderer.swift        # cmark-gfm C API wrapper
  FileWatcher.swift             # DispatchSource file monitoring
  MarkdownLinter.swift          # 9-rule pure Swift linting engine
  MarkdownSuggestions.swift     # Auto-suggest engine
  LanguagePlugin.swift          # Plugin protocol + registry
  HTMLSanitizer.swift           # XSS prevention
  Plugins/                      # CSV, HTML, Markdown plugins

Sources/MarkView/               # SwiftUI app (macOS 14+)
  ContentView.swift             # Split-pane editor + preview
  WebPreviewView.swift          # WKWebView with Prism.js
  Settings.swift                # 18 settings with theme/width/font enums
  ExportManager.swift           # HTML/PDF export

Sources/MarkViewMCPServer/      # MCP server for AI tool integration
  main.swift                    # stdio JSON-RPC server (preview_markdown, open_file)

Tests/TestRunner/               # 382 standalone tests (no XCTest)
Tests/VisualTester/             # 5 visual regression tests + WCAG contrast
Tests/FuzzTester/               # 10K random input crash testing
Tests/DiffTester/               # Differential testing vs cmark-gfm CLI
scripts/test-mcp.sh             # 5 MCP protocol + integration tests

See docs/ARCHITECTURE.md for full details.

Testing

# Run all tests (382 tests)
swift run MarkViewTestRunner

# Full verification (build + tests)
bash verify.sh

# Extended (fuzz + differential)
bash verify.sh --extended

Development

swift build                          # Build all targets
swift run MarkView                   # Launch app
swift run MarkView /path/to/file.md  # Launch with file
swift run MarkViewTestRunner         # Run tests

Support

If MarkView is useful to you, consider supporting development:

• GitHub Sponsors
• Star this repo to help others find it

License

MIT — see LICENSE.