PlantUML is an open-source tool allowing users to create UML diagrams from a plain text language. Developed by Arnaud Roques
License: Open Source
Mockingbird is a user-friendly diagramming tool that excels in visual design and collaboration, making it ideal for quick mockups and wireframes. In contrast, PlantUML focuses on text-based UML diagram creation, which is better suited for developers who prefer integrating diagrams with code documentation.