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Mermaid class diagram editor

Write class diagrams in Mermaid syntax and export clean visuals for architecture notes, API references, and technical reviews.

Use this page to connect a high-intent search query to the right problem-solution narrative.

At a glance

A Mermaid class diagram page for engineers who want UML-style relationships in a text-based workflow.

What a Mermaid class diagram is forTypical Mermaid class diagram usesWhen to reach for a class diagram
Rendered proof
Minimal Mermaid class diagram with inheritance and composition.
Theme · Atelier
Open this diagram in editor
CLASS HIERARCHY Animal +String name +int age +makeSound() void Dog +String breed +bark() void Owner +String name
View Mermaid sourcePlain-text diagram syntax — copy or edit directly.
diagram.mmd
1classDiagram
2  class Animal {
3    +String name
4    +int age
5    +makeSound() void
6  }
7  class Dog {
8    +String breed
9    +bark() void
10  }
11  class Owner {
12    +String name
13  }
14  Animal <|-- Dog
15  Owner "1" --> "*" Dog : owns

What a Mermaid class diagram is for

Class diagrams describe types, their fields and methods, and the relationships between them. They are useful when a codebase has multiple services, models, or contracts that teams need to agree on.

  • Show inheritance and composition
  • List public fields and methods
  • Capture multiplicities between classes

Typical Mermaid class diagram uses

Use class diagrams for onboarding docs, module boundaries, domain model reviews, and API design conversations where a shared vocabulary matters.

When to reach for a class diagram

Pick a class diagram when the question is 'what are the types and how do they relate?'. Pick a sequence diagram when the question is 'what is the order of calls?'.

FAQ

Mermaid class diagram editor — frequently asked questions

What is a Mermaid class diagram used for?

A Mermaid class diagram describes types, their fields and methods, and how they relate. It works well for onboarding docs, domain models, and API surface reviews.

How do I show inheritance in a Mermaid class diagram?

Use the `<|--` arrow between the parent and the child. For example, `Animal <|-- Dog` means Dog inherits from Animal.

Can I export a Mermaid class diagram as SVG?

Yes. Open the class diagram in the editor and export it as SVG or PNG. SVG keeps text sharp at any scale; PNG is the compatibility fallback.