CLI Reference

After pip install mmdr, the mmdr command is available on your PATH. It works similarly to the official mermaid-cli (mmdc), but starts in milliseconds — no browser to boot.

Basic usage

mmdr -i diagram.mmd -o output.svg
mmdr -i diagram.mmd -o output.png

The output format is inferred from the file extension. Supported: .svg, .png.

Stdin / stdout

Use - to read from stdin or write to stdout:

# stdin → stdout
echo 'flowchart LR; A-->B-->C' | mmdr -i - -o -

# stdin → file
echo 'flowchart LR; A-->B-->C' | mmdr -i - -o diagram.svg

# file → stdout
mmdr -i diagram.mmd -o -

Options

Flag	Default	Description
-i, --input	- (stdin)	Input .mmd file
-o, --output	- (stdout)	Output file
-e, --format	auto	Output format: svg or png
--backend	merman	Rendering backend: merman or mermaid-rs-renderer
-w, --width	—	Canvas width in pixels (PNG)
-H, --height	—	Canvas height in pixels (PNG)
-b, --background	transparent	Background color, e.g. '#ffffff' (PNG)
-t, --theme	modern	Color theme: modern or classic (mermaid-rs-renderer only)
--node-spacing	—	Horizontal node spacing (mermaid-rs-renderer only)
--rank-spacing	—	Vertical rank spacing (mermaid-rs-renderer only)
--aspect-ratio	—	Preferred aspect ratio, e.g. 16:9 (mermaid-rs-renderer only)
--info	—	Render Mermaid's built-in info diagram and print its text
--version	—	Print mmdr version and exit
-h, --help	—	Show help

Examples

# PNG with white background and fixed size
mmdr -i diagram.mmd -o output.png \
  --width 1200 \
  --height 800 \
  --background '#ffffff'

# Use the faster backend
mmdr -i diagram.mmd -o output.svg --backend mermaid-rs-renderer

# Classic Mermaid theme
mmdr -i diagram.mmd -o output.svg \
  --backend mermaid-rs-renderer \
  --theme classic

# Batch convert all .mmd files in a directory
for f in diagrams/*.mmd; do
    mmdr -i "$f" -o "${f%.mmd}.svg"
done

# Also works as a Python module
python -m mmdr -i diagram.mmd -o output.svg