Mermaid CLI

mermaid-cli

This is a command-line interface (CLI) for mermaid. It takes a mermaid definition file as input and generates an SVG/PNG/PDF file as output. There's basic support for converting mermaid code blocks embedded within Markdown files.

Installation

npm install -g @mermaid-js/mermaid-cli

Usage

Convert Mermaid mmd Diagram File To SVG

mmdc -i input.mmd -o output.svg

Note

See Alternative installations if you don't want to install the package globally.

Locate how to call the mmdc executable for your preferred method i.e. Docker, Yarn, NPM, local install, etc.

Examples

Create A PNG With A Dark Theme And Transparent Background

mmdc -i input.mmd -o output.png -t dark -b transparent

Adding custom icon packs to Mermaid

mermaid-cli supports two different ways to add custom icon packs to mermaid:

• Icon packs installed via npm install, e.g. @iconify-json/logos. These can be used via the --iconPacks @iconify-json/logos.
• Icon packs accessible via URI. These can either be URLs or local file:// URIs to local files. For example, to download the above @iconify-json/logos package from a CDN like jsDelivr, you can do --iconPacksAndUrls logos#https://cdn.jsdelivr.net/npm/@iconify-json/logos@1.2.14/icons.json.

Animating an SVG file with custom CSS

The --cssFile option can be used to inline some custom CSS. It's passed to Mermaid's themeCSS config option.

Please see ./test-positive/flowchart1.css for an example of a CSS file that has animations.

Warning: Inline CSS files may be blocked by your browser, depending on the HTTP Content-Security-Policy header of the website that hosts your SVG.

mmdc --input test-positive/flowchart1.mmd --cssFile test-positive/flowchart1.css -o docs/animated-flowchart.svg

Example output: docs/animated-flowchart.svg

Selecting the size of the created file

The --size value can be used to attempt to create a PNG of the given size, by setting a max-width on the SVG.

For narrow diagrams, this would decide set the max height, and for wide diagrams, this will set the max width.

For example, the following command will create a PNG of height 4000px:

mmdc --input test-positive/flowchart1.mmd --size 4000 -o output.png

![Note]

This may not work with all diagram types and/or may require useMaxWidth: true to be set in the diagram's config.

Transform a markdown file with mermaid diagrams

mmdc -i readme.template.md -o readme.md

This command transforms a markdown file itself. The mermaid-cli will find the mermaid diagrams, create SVG files from them and refer to those in the markdown output.

This:

### Some markdown

```mermaid
graph
   [....]
```

### Some more markdown

```mermaid
sequenceDiagram
   [....]
```

### Mermaid with custom title/desc

```mermaid
graph
   accTitle: My title here
   accDescr: My description here
   A-->B
```

Becomes:

### Some markdown

![diagram](./readme-1.svg)

### Some more markdown

![diagram](./readme-2.svg)

### Mermaid with custom title/desc

![My description here](./readme-3.svg "My title here")

Piping from stdin

You can easily pipe input from stdin. This example shows how to use a heredoc to send a diagram as stdin to mermaid-cli (mmdc).

cat << EOF  | mmdc --input -
    graph TD
    A[Client] --> B[Load Balancer]
EOF

See All Available Options

mmdc -h

Alternative installations

Use Docker/Podman:

docker pull minlag/mermaid-cli

or pull from Github Container Registry

docker pull ghcr.io/mermaid-js/mermaid-cli/mermaid-cli

or e.g. version 8.8.0

docker pull minlag/mermaid-cli:8.8.0

The container looks for input files in /data. So for example, if you have a diagram defined on your system in /path/to/diagrams/diagram.mmd, you can use the container to generate an SVG file as follows:

docker run --rm -u `id -u`:`id -g` -v /path/to/diagrams:/data minlag/mermaid-cli -i diagram.mmd

Or, if using Podman, instead do:

podman run --userns keep-id --user ${UID} --rm -v /path/to/diagrams:/data:z ghcr.io/mermaid-js/mermaid-cli/mermaid-cli -i diagram.mmd

The key differences in the podman command versus the docker command are:

• The addition of the --userns keep-id argument. This allows the container to keep the same UID as the current user's UID in the container namespace instead of mapping to a subuid. To learn more, see the userns=mode documentation.
• The addition of :z to the end of the volume mapping. This instructs podman to relabel the files in the volume with the SELinux label container_file_t, which allows processes in the container to access the files. See the "Labeling Volume Mounts" section of podman-run (1) for more info.

In previous version, the input files were mounted in /home/mermaidcli. You can restore this behaviour with the --workdir option:

docker run [...] --workdir=/home/mermaidcli minlag/mermaid-cli [...]

Use Node.JS API

It's possible to call mermaid-cli via a Node.JS API. Please be aware that the NodeJS API is not covered by semver, as mermaid-cli follows mermaid's versioning.

import { run } from "@mermaid-js/mermaid-cli";

await run(
    "input.mmd",
    "output.svg", // {optional options},
);

Install locally

Some people are having issues installing this tool globally. Installing it locally is an alternative solution:

npm install @mermaid-js/mermaid-cli
./node_modules/.bin/mmdc -h

Run with npx

npx is installed by default with NPM. It downloads and runs commands at the same time. To use Mermaid CLI with npx, you need to use the -p flag because the package name is different than the command it installs (mmdc). npx -p @mermaid-js/mermaid-cli mmdc -h

Install with brew

Warning

This method of installation is no longer supported. For more details, see the discussion. An old version of mermaid-cli can be installed with brew.

brew install mermaid-cli

Known issues

1. Linux sandbox issue
2. Docker permission denied issue
3. How to setup up mermaid to use already installed chromium?

For contributors

Contributions are welcome. See the contribution guide.