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Mermaid vs nomnoml: catalog facts
Mermaid	nomnoml
Free Free and open source under the MIT licence.	Free Free and open source under the MIT licence.
Web, Command line	Web, Command line
Diagrams are plain text, so they diff and review like code Rendered natively by GitHub, GitLab and most documentation generators	Readable syntax that resembles the drawn diagram Instant live preview in the browser
Layout is automatic, so fine control over positioning is limited Complex diagrams become hard to read in source form	Web editor stores diagrams only in browser local storage Smaller range of diagram types than PlantUML
Web application, Downloadable app	Downloadable app, Web application
Open source	Open source
License: MIT	License: MIT
Not stated if an account is needed	No account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked October 2, 2026

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