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Umbrello vs nomnoml: catalog facts
Umbrello	nomnoml
Free Free and open source under the GPL-2.0 or later.	Free Free and open source under the MIT licence.
Windows, Linux	Web, Command line
Supports nine UML and ER diagram types Generates code from diagrams in several languages	Readable syntax that resembles the drawn diagram Instant live preview in the browser
No macOS build listed Interface follows KDE conventions that may feel unfamiliar outside Plasma	Web editor stores diagrams only in browser local storage Smaller range of diagram types than PlantUML
Downloadable app	Downloadable app, Web application
Open source	Open source
License: GPL-2.0-or-later	License: MIT
No account needed	No account needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.