Using Mermaid Diagrams in Markdown and GitHub Docs

Mermaid in Markdown Documentation

One of Mermaid's greatest strengths is its native support in popular platforms. You can embed diagrams directly in Markdown files without any build tools, plugins, or image generation.

GitHub Native Support

GitHub renders Mermaid diagrams automatically in:

• README.md and other Markdown files
• Issues and Pull Requests
• Wiki pages
• Discussions

Simply use a fenced code block with the mermaid language identifier:

```mermaid
flowchart LR
    A[Push code] --> B[CI runs]
    B --> C{Tests pass?}
    C -->|Yes| D[Deploy]
    C -->|No| E[Fix & retry]
```

GitLab Support

GitLab also supports Mermaid natively in Markdown. The syntax is identical to GitHub — use a ```mermaid`` fenced code block.

Documentation Tools

Many documentation frameworks support Mermaid:

Tool	Support
Docusaurus	Built-in via @docusaurus/theme-mermaid
MkDocs	Via mkdocs-mermaid2-plugin
VitePress	Via vitepress-plugin-mermaid
Notion	Native support in code blocks
Obsidian	Built-in rendering

Fallback Strategies

For platforms that don't support Mermaid natively:

1. Pre-render to SVG — Use the Mermaid CLI (mmdc) to generate SVG files, then embed them as images.
2. Use a live editor link — Link to mermaid.live with the diagram code encoded in the URL.
3. GitHub Action — Automate SVG generation on push with actions like mermaid-js/mermaid-cli-action.

# Pre-render with Mermaid CLI
npx @mermaid-js/mermaid-cli -i diagram.mmd -o diagram.svg

Best Practices for Docs

1. Keep diagrams small — aim for 5-15 nodes. Split large diagrams into multiple focused ones.
2. Add alt text — wrap the diagram in an HTML <details> tag with a text description for accessibility.
3. Version control — since Mermaid diagrams are plain text, they diff cleanly in pull requests.
4. Provide context — always add a sentence or two above the diagram explaining what it shows.