UMLet vs Violet UML Editor

UMLet is a free, open-source tool for quickly sketching UML diagrams, including class, use case, sequence, state, deployment, and activity diagrams. Users edit diagram elements by changing text in a small markup dialect rather than configuring pop-up dialogs. UMLet is available as a stand-alone desktop application, an Eclipse plugin, the browser app UMLetino, and a Visual Studio Code extension. The desktop application exports to BMP, EPS, GIF, JPG, PDF, PNG, and SVG, can copy diagrams to the clipboard, and supports command-line batch conversion of UXF files. UMLetino runs in a browser without installation, stores diagrams in browser storage, and exports PNG. Custom elements can be made with Java code that UMLet compiles on the fly, but only in the stand-alone version. The desktop application requires Java and runs on Java platforms such as Windows, Linux, and macOS. UMLet identifies its license as GNU GPL 3.0. It does not generate code from models or reverse-generate models from code; round-trip engineering is not planned.

Violet UML Editor is a free, open-source application for drawing simple UML diagrams quickly. It supports class, activity, object, sequence, state and use case diagrams. The project describes Violet as easy to learn and use, and intended for developers, students, teachers and authors who need straightforward UML diagrams. Violet is licensed under GNU General Public License version 2.0 (GPLv2) and is written in Java, with Java Swing and Java SWT listed as interfaces. Linux, Mac and Windows are named operating systems, while the platform listing also includes web. The source repository directs users to SourceForge for downloads. Building from source requires Java Development Kit 17 or greater and Maven 3 or greater; the repository specifies running `mvn clean package` from the root directory to compile and package the project. The maintainer invites contributors to submit pull requests and says requests will be examined before contacting contributors. Violet has one listed plan: free, described as a completely free, cross-platform UML editor. Deployment is listed as both, with web, Windows and Linux among supported platforms.