mermaid-filter is a pandoc filter that adds support for mermaid syntax diagrams in markdown.

Write your diagrams in fenced code blocks as usual like this:

\```mermaid

sequenceDiagram
    Alice->>John: Hello John, how are you?
    John-->>Alice: Great!

and get this in rendered doc

1. npm install --global mermaid
2. npm install --global phantomjs
3. npm install --global raghur/mermaid-filter

pandoc -t html -F mermaid-filter -o something.html something.md

WINDOWS - you probably need mermaid-filter.cmd in the line above

You have a couple of formatting options via attributes of the fenced code block to control the rendering

• Image Format - Use ```{.mermaid format=svg} Default is png
• Width - Use ```{.mermaid width=400} default with is 500

Note that to specify options, you need to use the curly braces syntax and have the .mermaid class attached. Admittedly, this is uglier than the earlier syntax on top - but that's how Pandoc wants it.