mermaid-diagrams

Mermaid Diagrams

Create diagrams and visualizations using Mermaid markdown syntax.

Quick Reference

Mermaid diagrams are written in markdown code blocks with mermaid as the language identifier.

Flowchart

flowchart TD
    A[Start] --> B{Is it valid?}
    B -->|Yes| C[Process data]
    B -->|No| D[Show error]
    C --> E[Save to database]
    D --> F[Return to input]
    E --> G[End]
    F --> A

Flowchart Syntax

flowchart TD          %% TD = top-down, LR = left-right, RL, BT
    A[Rectangle]      %% Square brackets = rectangle
    B(Rounded)        %% Parentheses = rounded rectangle
    C{Diamond}        %% Curly braces = diamond/decision
    D[[Subroutine]]   %% Double brackets = subroutine
    E[(Database)]     %% Cylinder shape
    F((Circle))       %% Double parentheses = circle
    G>Asymmetric]     %% Flag shape

    A --> B           %% Arrow
    B --- C           %% Line without arrow
    C -.-> D          %% Dotted arrow
    D ==> E           %% Thick arrow
    E --text--> F     %% Arrow with label
    F -->|label| G    %% Alternative label syntax

Subgraphs

flowchart TB
    subgraph Frontend
        A[React App] --> B[Components]
        B --> C[Hooks]
    end
    
    subgraph Backend
        D[API Server] --> E[Database]
    end
    
    A -->|HTTP| D

Sequence Diagram

sequenceDiagram
    participant U as User
    participant C as Client
    participant S as Server
    participant D as Database

    U->>C: Click submit
    C->>S: POST /api/data
    activate S
    S->>D: INSERT query
    D-->>S: Success
    S-->>C: 200 OK
    deactivate S
    C-->>U: Show success message

Sequence Diagram Syntax

sequenceDiagram
    participant A as Alice
    participant B as Bob

    A->>B: Solid line with arrow
    A-->>B: Dotted line with arrow
    A-)B: Solid line with open arrow
    A--)B: Dotted line with open arrow
    
    activate B          %% Activation box
    B->>A: Response
    deactivate B
    
    Note over A,B: This is a note
    Note right of A: Note on right
    
    alt Condition true
        A->>B: Do this
    else Condition false
        A->>B: Do that
    end
    
    loop Every minute
        A->>B: Ping
    end
    
    opt Optional action
        A->>B: Maybe do this
    end