mermaid-cli

name	mermaid-cli
description	Render Mermaid diagram definitions to image files (SVG, PNG, PDF) from the command line. Use when asked to generate or convert Mermaid diagrams to visual output files.
compatibility	Requires @mermaid-js/mermaid-cli, available as a devDependency in this project. Run `npm install` then use `npx mmdc` or `npm run diagram --`.
allowed-tools	Bash(mmdc:*) Bash(npx:*) Bash(npm:*)

Diagram Rendering with mermaid-cli

Quick start

# via the project npm script (-- passes args to mmdc)
npm run diagram -- -i input.mmd -o output.svg

# or directly via npx (uses local devDependency)
npx mmdc -i input.mmd -o output.svg

Commands

Convert a file

# SVG (default)
mmdc -i diagram.mmd -o diagram.svg

# PNG
mmdc -i diagram.mmd -o diagram.png

# PDF
mmdc -i diagram.mmd -o diagram.pdf

Read from stdin

echo "graph LR; A-->B" | mmdc -i - -o out.svg

Common options

Flag	Long form	Description
-i	--input	Input .mmd file, or - for stdin
-o	--output	Output file path (.svg, .png, .pdf)
-t	--theme	Theme: default | dark | forest | neutral
-b	--backgroundColor	Background colour (white, transparent, #ffffff)
-w	--width	Canvas width in pixels (PNG only)
-H	--height	Canvas height in pixels (PNG only)
-s	--scale	Scale factor for PNG (default: 1)
-f	--configFile	Path to Mermaid config JSON
-C	--cssFile	Path to custom CSS file

Examples

# Dark-themed PNG at 1200 px wide
mmdc -i architecture.mmd -o architecture.png -t dark -w 1200

# Transparent-background SVG
mmdc -i flow.mmd -o flow.svg -b transparent

# Neutral theme with custom config
mmdc -i sequence.mmd -o sequence.svg -t neutral -f mermaid.config.json

Installation

@mermaid-js/mermaid-cli is a devDependency of this project. After npm install, invoke the binary via npx:

npx --no-install mmdc --version

If working outside this project and the command is not yet available locally:

npm install --save-dev @mermaid-js/mermaid-cli@latest

Reference

• mermaid-cli GitHub
• Mermaid diagram syntax