Complete Guide to Mermaid Diagrams

What is Mermaid?

Why Use Mermaid?

• Version Control: Diagrams are text files, so they can be tracked in Git alongside your code
• Quick Updates: Change a few lines of text instead of redrawing entire diagrams
• Consistency: Mermaid automatically handles layout and styling, ensuring consistent diagrams
• No Design Tools Required: No need for Visio, Lucidchart, or other expensive tools
• Documentation as Code: Keep diagrams in the same repository as your documentation
• Cross-Platform: Works in browsers, Node.js, and integrates with many platforms
• Free and Open Source: No licensing costs, active community support
• Multiple Diagram Types: Supports flowcharts, sequence diagrams, class diagrams, and more

Supported Diagram Types

Mermaid supports a wide variety of diagram types to cover different documentation needs:

flowchart TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Process]
    B -->|No| D[Alternative]
    C --> E[End]
    D --> E

sequenceDiagram
    participant User
    participant API
    participant DB
    User->>API: Request data
    API->>DB: Query
    DB-->>API: Results
    API-->>User: Response

classDiagram
    class Animal {
        +String name
        +int age
        +makeSound()
    }
    class Dog {
        +bark()
    }
    Animal <|-- Dog

stateDiagram-v2
    [*] --> Idle
    Idle --> Loading: Start
    Loading --> Success: Complete
    Loading --> Error: Fail
    Success --> [*]
    Error --> Idle: Retry

erDiagram
    CUSTOMER ||--o{ ORDER : places
    ORDER ||--|{ LINE_ITEM : contains
    CUSTOMER {
        int id
        string name
        string email
    }

gantt
    title Project Timeline
    dateFormat YYYY-MM-DD
    section Phase 1
    Design :a1, 2024-01-01, 30d
    Development :a2, after a1, 45d

pie title Distribution
    "Category A" : 42
    "Category B" : 30
    "Category C" : 28

gitGraph
    commit
    branch develop
    checkout develop
    commit
    checkout main
    merge develop

Getting Started with Mermaid

Best Practices

• Keep diagrams focused on a single concept or workflow
• Use meaningful labels that describe the actual business logic
• Break complex diagrams into smaller, interconnected diagrams
• Add comments using %% to explain complex sections
• Use consistent naming conventions throughout your diagrams
• Test your diagrams in the target environment before finalizing
• Include direction hints (TD, LR) to control layout when needed
• Use subgraphs to group related nodes in flowcharts
• Leverage styling options sparingly to maintain readability
• Version control your diagram source files alongside your code

Common Use Cases

Additional Resources

• Official Mermaid Documentation
• Mermaid GitHub Repository
• Mermaid Syntax Reference