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SuperHTML vs Nu Html Checker: catalog facts
SuperHTML	Nu Html Checker
Free Free and open source under the MIT licence.	Free Free to use on the W3C website.
Windows, Command line	Web
Validation and formatting in one tool Works as a language server in editors	Checks against current HTML conformance rules rather than old doctypes Accepts a URL, a file upload or pasted markup
Focused on HTML only No formal releases listed on the repository	Checks one document at a time Behavior is described as experimental and subject to change
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.