AI UML class diagram generator from text

Describe classes, attributes, and inheritance. Get a Mermaid UML class diagram.

Try one of these — click to open in the generator

UML class diagram for geometric shapes: abstract Shape with area() method, subclasses Circle (radius: double), Rectangle (width, height), Triangle (base, height). Each overrides area().

Employee hierarchy with roles

Employee class hierarchy: Person (name, email, phone). Employee extends Person (employeeId, salary, hireDate). Manager extends Employee (directReports list). Contractor extends Person (contractEnd, hourlyRate). Show visibility markers and getters.

E-commerce domain model

E-commerce domain model: Customer has many Orders. Order has many LineItems. LineItem references a Product with unitPrice and quantity. Product has category, sku, price. Show associations with cardinality and key methods.

Payment processor with strategy pattern

Payment processing using strategy pattern: PaymentProcessor uses a PaymentStrategy interface. Concrete strategies: StripeStrategy, PayPalStrategy, CryptoStrategy. Each implements charge(amount) and refund(txId). Show interface implementation and composition.

When to use this

Class diagrams are the standard vocabulary for talking about software structure. Reach for them when you need to communicate the shape of an object-oriented codebase: which types exist, what attributes and methods they have, and how they relate through inheritance, composition, and association. Where they shine: onboarding docs ("here's how our domain model is organized"), design RFCs proposing a new class hierarchy or refactor, and technical interviews where you need to sketch out a design in the whiteboard. They're also the go-to for documenting design patterns — factory, strategy, observer, visitor all have a canonical class diagram shape that readers recognize instantly. Mermaid's classDiagram supports the full UML notation you'd expect: visibility markers (`+` public, `-` private, `#` protected, `~` package), abstract classes and methods, interfaces via the `<<interface>>` stereotype, generic types, and every relationship (inheritance `<|--`, composition `*--`, aggregation `o--`, association `--`, dependency `..>`). It stops short of full UML — no swimlanes, no full activity semantics — which for most engineering docs is a feature, not a bug. If you need those, you're probably reaching for the wrong tool.

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