Describe your design. The AI figures out whether it's a class, sequence, or state diagram.
UML class diagram for a library system: Book (isbn, title, author), Member (id, name, email), Loan (dueDate, returnedDate) links a Member to a Book. Librarian extends Member with canManageCatalog boolean. Show associations and cardinality.
Try it →UML sequence diagram for a login handshake: client sends credentials to auth service, auth service verifies against the user database, on success issues a JWT, client stores the token and uses it for subsequent API calls.
Try it →UML state diagram for an order: created -> paid -> shipped -> delivered. From created, can be cancelled. From paid, can be refunded. Cancelled and refunded are terminal.
Try it →UML class diagram using the strategy pattern: PaymentProcessor depends on a PaymentStrategy interface. Concrete strategies StripeStrategy and PayPalStrategy each implement charge(amount). Show the interface, implementations, and the composition relationship.
Try it →Not sure yet whether your design doc needs a structure view or a behavior view? Describe the design in plain English and let the AI classify it — you can always regenerate as a different UML type if it guesses wrong.
Before a design review, sketch the relevant classes, the critical call sequence, or the object's lifecycle — whichever best explains the change you're proposing.
Students and bootcamp instructors use this to see canonical UML notation quickly — visibility markers, arrow types, lifelines — without opening a UML modeling tool.
Sketch a class hierarchy or a sequence of API calls the way you'd draw it on a whiteboard, then export it to include in a take-home submission or portfolio.
Factory, strategy, observer, and other classic patterns each have a canonical UML shape. Describe the pattern and get the standard diagram other engineers will recognize instantly.
The full UML specification defines 14 diagram types, but in day-to-day engineering work, three do almost all the heavy lifting: class diagrams (structure — what types exist, what they have, how they relate), sequence diagrams (behavior over time — who calls whom, in what order), and state diagrams (behavior over state — what states exist, which transitions are legal). This page is a UML hub: describe your design in plain English and the AI figures out which of the three fits, then draws it.
Reach for a class diagram when the question is "what does the type system look like" — domain models, DDD aggregates, library APIs. Reach for a sequence diagram when the question is "what's the order of calls between actors" — API handshakes, distributed transactions, authentication flows. Reach for a state diagram when the question is "what states can this object be in, and what moves it between them" — order lifecycles, workflow statuses, protocol states.
If you already know exactly which of the three you need, the dedicated pages (class diagram generator, sequence diagram generator, state diagram generator) go deeper on that one type — more examples, a longer syntax rundown, and type-specific FAQ. This page is for when you know you want "a UML diagram" but haven't decided which shape the answer takes — describe the design, and let the AI choose.
Not sure how to phrase your prompt? Chat mode lets AI ask 2-3 clarifying questions about actors, events, and edge cases — then draws.
Read our in-depth tutorials — symbols, structures, 9 rules, and copy-paste prompt templates for real-world flows.
Describe classes, attributes, and inheritance. Get a Mermaid UML class diagram.
Turn an API description into a sequence diagram with actors and arrows.
Describe a state machine. Get a Mermaid state diagram with transitions.