kUML vs UMLet

kUML is a modeling tool that expresses UML 2.x, SysML 2, C4, BPMN 2.0, and ERM as a type-safe Kotlin DSL. It supports all 14 UML 2.x diagram types, with compile-time validation and IDE support. Built-in transformations generate JPA, OpenAPI 3.0 YAML, Kubernetes manifests, and Dockerfiles. Integrations include CLI, Gradle, IntelliJ, Obsidian, Asciidoctor, and VS Code. For interoperability, it supports Structurizr DSL round-tripping and optional XMI through the kuml-io-emf module. kUML also includes an MCP server for agent introspection and a kuml ai subcommand for AI-assisted modeling. It is free and open source under Apache 2.0, with no paid plans or feature limits stated. It runs on Windows, macOS, Linux, and the web, and can be deployed both self-hosted and through other means. Install options include packages for major desktop systems, Docker, and Maven Central library modules. Rendering Kotlin scripts executes their source code, so use only scripts or workspaces you trust.

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.