Free Mermaid Diagram Guide & Tutorial

Getting Started with Mermaid

Mermaid is a powerful diagramming and charting tool that uses text and code to generate diagrams. It's perfect for creating flowcharts, sequence diagrams, Gantt charts, and more.

What is Mermaid?

Mermaid lets you create diagrams and visualizations using text. It's widely used in documentation, README files, and technical documentation because it's easy to write, version-control friendly, and produces beautiful diagrams.

Basic Flowchart

Flowcharts are one of the most common diagram types. They show processes, decisions, and flows.

Simple Flowchart Example

graph TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Action 1]
    B -->|No| D[Action 2]
    C --> E[End]
    D --> E

Flowchart Syntax

• graph TD - Top Down flowchart
• graph LR - Left Right flowchart
• [Text] - Rectangle node
• {Text} - Diamond decision node
• --> - Arrow connection
• -->|Label| - Labeled arrow

Sequence Diagrams

Sequence diagrams show interactions between different components or actors over time.

Sequence Diagram Example

sequenceDiagram
    participant User
    participant Browser
    participant Server
    
    User->>Browser: Enter URL
    Browser->>Server: HTTP Request
    Server-->>Browser: HTML Response
    Browser-->>User: Display Page

Sequence Diagram Syntax

• participant - Defines an actor/component
• ->> - Solid arrow (request)
• -->> - Dashed arrow (response)
• ->> with text - Message label

Class Diagrams

Class diagrams are used in object-oriented design to show classes, relationships, and inheritance.

Class Diagram Example

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

Gantt Charts

Gantt charts are perfect for project planning and timeline visualization.

Gantt Chart Example

gantt
    title Project Timeline
    dateFormat YYYY-MM-DD
    section Planning
    Requirements    :a1, 2024-01-01, 30d
    Design         :a2, after a1, 20d
    section Development
    Backend        :a3, after a2, 40d
    Frontend       :a4, after a2, 35d

Converting Diagrams to Images

Once you've created your Mermaid diagram, you can easily convert it to various image formats.

Steps to Convert:

1. Write or paste your Mermaid code in the editor
2. See the live preview update in real-time
3. Select your desired export format (PNG, JPG, PDF, or SVG)
4. Click "Download Image" to save your diagram

Best Practices

• Keep it simple: Don't overcrowd your diagrams with too many elements
• Use meaningful labels: Make sure your node and edge labels are clear
• Consistent styling: Use consistent node shapes for similar concepts
• Test your syntax: Use the live preview to catch errors early
• Save your work: Copy your Mermaid code to save it for later

Common Issues and Solutions

Diagram not rendering?

Check for syntax errors. Common issues include:

• Missing diagram type declaration
• Incorrect arrow syntax
• Unclosed brackets or parentheses
• Invalid node IDs or labels

Export not working?

Make sure:

• The diagram has rendered successfully in the preview
• Your browser supports the export format
• You have sufficient memory for large diagrams