Compare software

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