mermaid-js

Mermaid.js v11

Overview

Create text-based diagrams using Mermaid.js v11 declarative syntax. Convert code to SVG/PNG/PDF via CLI or render in browsers/markdown files.

Quick Start

Basic Diagram Structure:

{diagram-type}
  {diagram-content}

Common Diagram Types:

• flowchart - Process flows, decision trees
• sequenceDiagram - Actor interactions, API flows
• classDiagram - OOP structures, data models
• stateDiagram - State machines, workflows
• erDiagram - Database relationships
• gantt - Project timelines
• journey - User experience flows

See references/diagram-types.md for all 24+ types with syntax.

Creating Diagrams

Inline Markdown Code Blocks:

```mermaid
flowchart TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Action]
    B -->|No| D[End]
```

Configuration via Frontmatter:

```mermaid
---
theme: dark
---
flowchart LR
    A --> B
```

Comments: Use %% prefix for single-line comments.

CLI Usage

Convert .mmd files to images:

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

# Basic conversion
mmdc -i diagram.mmd -o diagram.svg

# With theme and background
mmdc -i input.mmd -o output.png -t dark -b transparent

# Custom styling
mmdc -i diagram.mmd --cssFile style.css -o output.svg

See references/cli-usage.md for Docker, batch processing, and advanced workflows.

JavaScript Integration

HTML Embedding:

<pre class="mermaid">
  flowchart TD
    A[Client] --> B[Server]
</pre>
<script src="https://cdn.jsdelivr.net/npm/mermaid@latest/dist/mermaid.min.js"></script>
<script>mermaid.initialize({ startOnLoad: true });</script>

See references/integration.md for Node.js API and advanced integration patterns.

Configuration & Theming

Common Options:

• theme: "default", "dark", "forest", "neutral", "base"
• look: "classic", "handDrawn"
• fontFamily: Custom font specification
• securityLevel: "strict", "loose", "antiscript"