UMLet
UMLet provides free, open source UML drawing with a simple interface for making diagrams, including sequence and activity diagrams.
About UMLet
UMLet is a UML tool built for fast sketching of diagrams. Elements are edited through a text panel using a small markdown dialect instead of pop-up dialogs, and the tool supports class, use case, sequence, state, deployment and activity diagrams. Sequence and activity diagrams can be generated from plain text, and diagrams can be exported to EPS, PDF, JPG, SVG or the system clipboard. The homepage lists version 15.1, with a relation bug fix, a log library update and dark mode cleanup.
Key features
- Text-panel element editing with a small markdown dialect
- Generate sequence and activity diagrams from plain text
- Export to EPS, PDF, JPG, SVG and clipboard
- Create custom UML elements by editing Java code, compiled on the fly
- Stand-alone app for Windows, macOS and Linux
- Also available as Eclipse plugin, VS Code extension and web app UMLetino
Best for: Developers, students and teams that want to produce UML sketches quickly without working through dialog boxes.
Good for
- Free and open source under GNU GPL 3.0, per the homepage
- Same tool available across Windows, macOS, Linux, Eclipse, VS Code and the web
- Elements and palettes can be tailored, and custom element types added at runtime
Watch out for
- Creating custom elements requires changing Java code
- Diagram editing relies on text input rather than a purely graphical interface
UMLet at a glance
- Website
- umlet.com
- Category
- Design & Creative › Charts & Data Visualization
- Type
- Online tool
- Pricing
- Not confirmed. Check the site
- Platforms
- Linux, macOS, Web, Windows
- Open source
- Not stated
- Language
- English
- Last checked
- Oct 5, 2026 · Online when checked
- Listed
- Oct 5, 2026
Guides for Charts & Data Visualization
UMLet alternatives
Tools and sites you could use instead, ranked by how closely they match.
PlantText provides an online editor for PlantUML code and generates class, sequence, activity, and state diagrams.
SankeyMATIC builds flow diagrams for comparing quantities across stages, with examples covering budgets, results, and processes.
Kroki provides one API for generating diagrams from textual descriptions using libraries such as Mermaid, PlantUML, Graphviz, and D2.
text2diagram creates diagrams and charts from text descriptions, with real-time collaboration and document permissions listed on its page.
Kroki CLI converts diagram files through the Kroki service, inferring diagram type from the file extension by default.
Open source
24 alternatives
Dia is free, open source drawing software for structured diagrams, with downloads, shapes, and documentation.
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UMLet FAQ
Which platforms and integrations does UMLet support?
The homepage lists a stand-alone app for Windows, macOS and Linux, an Eclipse plugin, a Visual Studio Code extension, and a web app called UMLetino.
What export formats are available?
Diagrams can be exported to EPS, PDF, JPG and SVG, or copied to the system clipboard.
Can I add my own UML element types?
Yes. An element's look can be modified at run time by changing a few lines of Java code, which UMLet compiles on the fly so new element types can be added without leaving the tool.
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