A lightweight, native macOS Markdown viewer built for developers.
MDViewer was created out of a simple need: a fast, minimal way to read .md files when working from the terminal with tools like Claude Code or Codex. It renders Markdown beautifully without the overhead of a browser or a full editor.
MDViewer started as a viewer — but we wanted editing too, so it now includes a built-in split-view editor.
- Instant rendering — opens and renders Markdown files immediately
- Live reload — watches for file changes and re-renders as you save
- Table of contents — auto-generated sidebar from headings with smooth scroll
- Syntax highlighting — 40 languages via Shiki v4
- Math equations — inline and block LaTeX via KaTeX
- Mermaid diagrams — flowcharts, sequence diagrams, Gantt charts, and more
- Smart link handling — local
.mdlinks open in-app; external links open in the browser - Export to PDF — one-click PDF export preserving all styles
- Signed & notarized — Developer ID signing and Apple notarization
Toggle the built-in editor with ⌘E or the pencil button in the toolbar.
- Split view: Editor on the left, live preview on the right
- Save: ⌘S saves changes to the current file
- Unsaved changes are indicated by the Save button becoming active
- Closing the window with unsaved changes prompts Save / Discard / Cancel
- macOS 14 Sonoma or later
- Apple Silicon (M1 or later)
- Download the latest
MDViewer-x.x.x.zipfrom the Releases page - Unzip and drag
MDViewer.appto your Applications folder - Double-click any
.mdfile — or drop it onto the MDViewer icon in the Dock
Requires Xcode 15 or later.
git clone https://github.com/devicemanager/mdviewer.git
cd mdviewer
open MDViewer.xcodeprojBuild and run with ⌘R. No Swift Package dependencies — all vendor libraries are bundled in MDViewer/Resources/Web/vendor/.
| Layer | Technology |
|---|---|
| UI framework | SwiftUI + AppKit |
| Rendering engine | WKWebView |
| Markdown parser | marked v18 |
| Syntax highlighting | Shiki v4 |
| Math | KaTeX v0.17 |
| Diagrams | Mermaid v11 |
| File watching | DispatchSource (kqueue) |
All bundled libraries are permissively licensed (MIT, except DOMPurify which is Apache-2.0 / MPL-2.0). See THIRD_PARTY_NOTICES.md for full license texts.
| Library | Version | License |
|---|---|---|
| marked | 18.0.6 | MIT |
| Shiki | 4.3.1 | MIT |
| KaTeX | 0.17.0 | MIT |
| Mermaid | 11.16.0 | MIT |
| DOMPurify | 3.4.12 | Apache-2.0 / MPL-2.0 |
MDViewer was originally created by Masanori Sakai (@Masakai). This repository is a fork maintained by @devicemanager, which adds a Quick Look preview extension — full Markdown rendering (including KaTeX math and Mermaid diagrams) directly in Finder — along with related refinements.
Sincere thanks to Masanori Sakai for creating and open-sourcing MDViewer.
MDViewer is released under the MIT License.
© 2026 Masanori Sakai