Mermaid

Quick Reference

Flowchart Basics

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

Sequence Diagram Basics

sequenceDiagram
    Client->>+Server: Request
    Server->>+Database: Query
    Database-->>-Server: Results
    Server-->>-Client: Response

Class Diagram Basics

classDiagram
    class Animal {
        +String name
        +makeSound()
    }
    Animal <|-- Dog
    Animal <|-- Cat

Workflow

Creating a New Diagram

1. Identify diagram type - Match the user's need to the appropriate diagram type
2. Consult reference - Read the relevant reference file in references/
3. Draft diagram - Write the Mermaid code following syntax rules
4. Validate - Check for common issues (proper indentation, valid connections)
5. Refine - Add styling or improve layout as needed

Debugging Diagrams

Common issues to check:

• Missing or extra brackets in node definitions
• Incorrect arrow syntax (--> vs -> vs --)
• Unmatched quotes in labels
• Invalid characters (use entity codes: #quot;, #lt;, #gt;)
• Incorrect indentation (critical for mindmaps, Gantt)
• Missing diagram type declaration

Choosing the Right Diagram Type

Reference Documentation

Detailed syntax documentation is available in references/:

Core Diagrams

• flowcharts.md - Nodes, edges, subgraphs, styling
• sequence.md - Participants, messages, loops, notes
• class.md - Classes, relationships, cardinality
• state.md - States, transitions, composite states
• entity-relationship.md - Entities, attributes, relationships

Charts and Data

• gantt.md - Tasks, milestones, dependencies
• pie.md - Slices, labels, showData
• xychart.md - Bar charts, line charts, axes
• quadrant.md - Axes, quadrants, data points
• sankey.md - Flow diagrams, nodes, links

Specialized Diagrams

• mindmap.md - Hierarchical concepts, icons
• timeline.md - Chronological events, sections
• gitgraph.md - Commits, branches, merges
• architecture.md - Services, groups, edges
• journey.md - User experiences, satisfaction scores
• kanban.md - Columns, tasks, metadata
• block.md - Precise layout control, columns

Configuration

• styling.md - Themes, colors, fonts, configuration

Grep Patterns for References

To find specific syntax, use these patterns:

# Find all node shape syntax
grep -r "shape\|rectangle\|circle\|diamond" references/

# Find arrow/edge syntax
grep -r "-->\\|--\\|-.->\\|==>" references/

# Find styling examples
grep -r "classDef\\|style\\|theme" references/

# Find configuration options
grep -r "init:\\|config:" references/

Best Practices

1. Start simple - Begin with basic syntax, add complexity gradually
2. Use meaningful IDs - userAuth is better than A for node IDs
3. Label edges - Add text to arrows when relationships aren't obvious
4. Group related items - Use subgraphs, sections, or groups
5. Consider direction - TD (top-down) for hierarchies, LR (left-right) for processes
6. Apply consistent styling - Use classes for repeated styles
7. Test incrementally - Add a few elements at a time to catch errors early

Common Syntax Patterns

Special Characters in Labels

flowchart LR
    A["Text with (parentheses)"]
    B["Text with #quot;quotes#quot;"]

Adding Notes

sequenceDiagram
    Alice->>Bob: Hello
    Note right of Bob: Bob thinks
    Bob-->>Alice: Hi!

Styling Nodes

flowchart LR
    A:::highlight --> B
    classDef highlight fill:#ff0,stroke:#f00,stroke-width:4px

Conditional Branches

flowchart TD
    A{Is valid?}
    A -->|Yes| B[Process]
    A -->|No| C[Error]

Known Limitations

• No inline images (except icons in some diagram types)
• Limited interactive features in static renders
• Some diagram types are in beta (-beta suffix)
• Complex layouts may require manual adjustment
• Cross-browser rendering may vary slightly

Troubleshooting

"Parse error" or diagram not rendering

• Check diagram type declaration is first line
• Verify all brackets/quotes are matched
• Look for unsupported characters

Diagram looks wrong

• Check direction (TD, LR, etc.)
• Verify edge syntax matches diagram type
• Review indentation (especially for Gantt, mindmap)

Styling not applying

• Ensure %%{init: is at very start of diagram
• Check for JSON syntax errors (no trailing commas)
• Verify variable names are correct for diagram type