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Gaphor vs Mermaid: catalog facts
Gaphor	Mermaid
Free The software is free under its open-source licence. Hosting, hardware and external…	Free Free and open source under the MIT licence.
Windows, macOS, Linux	Web, Command line
It keeps a real UML 2 data model behind the diagrams, so elements are reused across views rather…	Diagrams are plain text, so they diff and review like code Rendered natively by GitHub, GitLab and most documentation generators
It is a modelling tool rather than a quick diagram editor, and it does not generate code from…	Layout is automatic, so fine control over positioning is limited Complex diagrams become hard to read in source form
Downloadable app	Web application, Downloadable app
Open source	Open source
License: Apache-2.0	License: MIT
Not stated if an account is needed	Not stated if an account is 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 September 22, 2026

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