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HTMLHint vs Nu Html Checker: catalog facts
HTMLHint	Nu Html Checker
Free Free and open source, supported through Open Collective.	Free Free to use on the W3C website.
Windows, macOS, Linux, Command line	Web
Rules can be switched on, off or customised per project Runs from the command line or in a build pipeline	Checks against current HTML conformance rules rather than old doctypes Accepts a URL, a file upload or pasted markup
Checks HTML only, not CSS or JavaScript Needs Node.js and npm for the command-line version	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.