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SequenceDiagram.org vs Mermaid: catalog facts
SequenceDiagram.org	Mermaid
Free Free to use, supported by optional Patreon donations.	Free Free and open source under the MIT licence.
Web	Web, Command line
Text notation and drag and drop editing in one tool Saves to local files, Google Drive, OneDrive or browser storage	Diagrams are plain text, so they diff and review like code Rendered natively by GitHub, GitLab and most documentation generators
Only draws sequence diagrams No built-in real-time collaboration mentioned	Layout is automatic, so fine control over positioning is limited Complex diagrams become hard to read in source form
Web application	Web application, Downloadable app
Closed source	Open source
License not stated	License: MIT
No account 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 October 2, 2026	Official website Full listing and sources Checked September 22, 2026

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