Learn Class Diagrams — a key concept for LLD interviews.
Interactive — Try it yourself!
How to use
1See 4 interactive class boxes for a Library system
2Click a class (Library, Book, Member, Loan) to highlight its relationships
3See composition lines (Library→Book) and association (Member→Loan)
4Try the challenge: "Which relationship is between Member and Book?"
In a nutshell
Class diagrams show the static structure of a system — classes, attributes, methods, and relationships. They're the most common UML diagram in LLD interviews.