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Nu Html Checker vs HTML-validate: catalog facts
Nu Html Checker	HTML-validate
Free Free to use on the W3C website.	Free Free to use, with the source code published on GitLab.
Web	Command line
Checks against current HTML conformance rules rather than old doctypes Accepts a URL, a file upload or pasted markup	Validates entirely offline, so no markup is uploaded Handles HTML fragments inside Vue.js and AngularJS components
Checks one document at a time Behavior is described as experimental and subject to change	Command-line and tooling oriented, with no graphical interface Checks markup only, not CSS or accessibility in a browser
Web application	Downloadable app
Closed source	Closed source
License not stated	License not stated
No account needed	No account needed
Needs internet	Works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked October 2, 2026

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