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WebSequenceDiagrams vs Mermaid: catalog facts
WebSequenceDiagrams	Mermaid
Free Described on its site as a free online tool.	Free Free and open source under the MIT licence.
Web	Web, Command line
Diagrams are written as plain text instead of drawn by hand Runs in the browser with nothing to install	Diagrams are plain text, so they diff and review like code Rendered natively by GitHub, GitLab and most documentation generators
Only draws sequence diagrams Little public detail on export options and paid features	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
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 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.