Free Class Diagram Generator
Create UML class diagrams with our free tool. Classes, attributes, methods, and relationships.
- Class boxes with compartments
- Visibility modifiers (+, -, #)
- Inheritance and interfaces
- Association and composition
- Export as PNG, SVG, or PDF
Frequently Asked Questions
What should a class diagram show?
Class diagrams show class names, attributes (properties), methods (operations), visibility modifiers, and relationships between classes like inheritance and association.
What's the difference between composition and aggregation?
Composition (filled diamond) means the child cannot exist without the parent—strong ownership. Aggregation (empty diamond) means the child can exist independently—weak ownership.
How detailed should class diagrams be?
Include key classes and their main relationships. For detailed documentation, show all attributes and methods. For high-level design, show only class names and relationships.