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SuperHTML vs W3C Markup Validation Service: catalog facts
SuperHTML	W3C Markup Validation Service
Free Free and open source under the MIT licence.	Free A free service run by the W3C.
Windows, Command line	Web
Validation and formatting in one tool Works as a language server in editors	Validate by URL, file upload or direct input Choice of character encoding and document type
Focused on HTML only No formal releases listed on the repository	HTML5 validation is marked experimental Modern HTML is better served by the separate Nu Html Checker
Downloadable app	Web application
Open source	Closed source
License: MIT	License not stated
No account needed	No account needed
Works offline	Needs internet
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 23, 2026

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