mdr 0.4.0

A lightweight Markdown viewer with live reload and multiple rendering backends
mdr-0.4.0 is not a library.

Why mdr?

Built for the LLM era. AI tools generate Markdown constantly — code documentation, technical specs, analysis reports — packed with diagrams, tables, and structured content. You need a fast way to read them.

Most developers end up previewing Markdown in VS Code, pasting into a browser, or squinting at raw text in the terminal. None of these handle Mermaid diagrams. None are instant. mdr is.

  • One command — mdr file.md and you're reading, not editing
  • Native Rust binary — no Electron, no Node.js, no npm, starts in milliseconds
  • Mermaid diagrams — flowcharts, sequence diagrams, pie charts rendered as SVG natively (no headless browser)
  • Three backends — full GUI (egui), native webview (WebKit/WebView2), or terminal UI (TUI) over SSH
  • Live reload — edit your file or let your AI tool regenerate it, see changes instantly
  • In-document search — Ctrl+F / / to find text across all backends
  • Fully keyboard-driven — every backend quits, scrolls, searches and navigates from the keyboard

Backends

mdr offers multiple rendering backends, selectable at runtime:

Backend Stack Strengths
egui (default) Pure Rust GPU rendering Single static binary, fast startup, cross-platform
webview OS native WebView (WebKit/WebView2) GitHub-quality HTML/CSS rendering, full CSS support
tui Terminal UI (ratatui + crossterm) Works over SSH, no GUI needed, keyboard-driven

Install

From source

git clone https://github.com/CleverCloud/mdr.git
cd mdr
cargo install --path .

Build with specific backends only

# egui only (smaller binary, no WebView dependency)
cargo install --path . --no-default-features --features egui-backend

# webview only
cargo install --path . --no-default-features --features webview-backend

Homebrew (macOS/Linux)

brew install CleverCloud/misc/mdr

Snap (Linux)

sudo snap install --edge mdr-markdown-renderer

Note: The snap command is mdr-markdown-renderer, not mdr. You can create an alias: sudo snap alias mdr-markdown-renderer mdr

Scoop (Windows)

scoop bucket add clevercloud https://github.com/CleverCloud/scoop-bucket
scoop install mdr

Chocolatey (Windows)

choco install mdr

WinGet (Windows)

winget install CleverCloud.mdr

Nix

nix run github:CleverCloud/mdr

Pre-built binaries

Download from the Releases page for macOS, Linux, and Windows.

Usage

# Open with default backend (egui)
mdr README.md

# Open with webview backend
mdr --backend webview README.md

# Open in terminal (TUI)
mdr --backend tui README.md

# Never touch the network (remote images are left unresolved)
mdr --offline README.md

# Show help
mdr --help

Clicking an http(s) link opens it in your system browser; a link to another local .md file opens that file in mdr.

GUI (egui) keybindings

Key Action
q, Esc, Ctrl/Cmd+Q, Ctrl/Cmd+W Quit
Ctrl/Cmd+F Search in the document
Esc Close the search (quits when no search is open)
F10 Show or hide the table of contents
j / ↓, k / ↑ Scroll down / up
Space / PgDn, PgUp Page down / up
g / Home, G / End Go to top / bottom

On macOS the shortcuts use ⌘, not ⌃.

Webview keybindings

Press ? in the webview backend for this list.

Key Action
Ctrl/Cmd+Q Close the window
Ctrl/Cmd+F Search in the document
n / N Next / previous search match
Esc Close search, help or the expanded image
j / ↓, k / ↑ Scroll down / up
Space / PgDn, PgUp Page down / up
g / Home, G / End Go to top / bottom
Ctrl/Cmd + + / - / 0 Zoom in / out / reset
Ctrl/Cmd+B Show or hide the table of contents
Ctrl/Cmd+D Switch between the light and dark theme
Ctrl/Cmd+P Print or export to PDF
? Show or hide the shortcut list

Ctrl/Cmd+D overrides the system colour scheme for the current window; without it the theme follows prefers-color-scheme.

TUI keybindings

Key Action
q / Esc Quit
j / ↓ Scroll down
k / ↑ Scroll up
Space / PgDn Page down
PgUp Page up
g / Home Go to top
G / End Go to bottom
Tab Switch focus between TOC and content
Enter Navigate to selected TOC heading
/ or Ctrl+F Open search
n Next search match
N Previous search match

Features

  • Full GFM support — tables, task lists, strikethrough, footnotes, autolinks
  • Syntax highlighting — code blocks with language detection (via syntect)
  • Mermaid diagrams — flowcharts, sequence diagrams, pie charts, and more (via mermaid-rs-renderer)
  • Table of Contents — auto-generated sidebar from headings with click-to-navigate
  • Live reload — file watching with 300ms debounce, updates on save
  • Dark/Light theme — follows OS theme, overridable with Ctrl/Cmd+D (webview backend)
  • YAML front matter — recognised as metadata, so it is neither rendered nor listed in the TOC
  • Unique heading anchors — repeated headings get setup, setup-1, … as GitHub does

Images

Images are inlined into the document before rendering, so nothing is fetched while you read.

  • Local images resolve relative to the Markdown file, and may live anywhere inside the enclosing project — the nearest ancestor directory holding a .git, .hg, .svn or .jj. That makes the usual docs/page.md → ![](../images/schema.png) layout work. Outside that root, and above your home directory, images are refused.
  • Remote images (http/https, typically README badges) are downloaded once, cached for the lifetime of the process, and embedded as data: URIs. Responses larger than 16 MB are ignored.
  • mdr --offline file.md disables every network access; remote images are then left unresolved. The same can be set permanently with offline #true in the config file.

Mermaid Support

Mermaid code fences are rendered as SVG diagrams:

```mermaid
graph TD
    A[Input] --> B[Process]
    B --> C[Output]
```

Supported diagram types: flowchart, sequence, pie, class, state, ER, gantt.

Note: Diamond/decision nodes ({text}) are not yet supported by the underlying renderer. Use square brackets as a workaround.

Architecture

src/
├── main.rs              # CLI (clap), backend dispatch
├── core/
│   ├── markdown.rs      # GFM parsing (comrak) + CSS
│   ├── mermaid.rs       # Mermaid → SVG rendering
│   ├── toc.rs           # Heading extraction for TOC
│   ├── slug.rs          # Heading anchors, shared by the renderer and the TOC
│   ├── sanitize.rs      # Strips scripts and event handlers from raw HTML
│   ├── paths.rs         # Which directory tree images may be read from
│   ├── net.rs           # Remote image fetching (respects --offline)
│   └── watcher.rs       # File watching (notify, 300ms debounce)
└── backend/
    ├── egui.rs          # egui/eframe backend
    ├── tui.rs           # ratatui/crossterm TUI backend
    └── webview.rs       # wry/tao WebView backend

Building

Requires Rust 1.95 or later (the floor comes from kdl; the MSRV is checked in CI).

# All backends (default)
cargo build --release

# Run tests
cargo test

# Run clippy exactly as CI does
cargo clippy --all-features --all-targets -- -D warnings

Linux dependencies

sudo apt-get install libgtk-3-dev libwebkit2gtk-4.1-dev libxdo-dev libgl1-mesa-dev

Releases

Pre-built binaries are available on the Releases page for:

  • macOS (Apple Silicon + Intel)
  • Linux (x86_64 + aarch64)
  • Windows (x86_64)

Release notes are the matching section of CHANGELOG.md, so add it before pushing the tag.

To create a release, push a version tag:

git tag v0.4.0
git push origin v0.4.0

License

MIT

Contributing

Issues and PRs welcome at github.com/CleverCloud/mdr.