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HTML-validate vs The Nu Html Checker: catalog facts
HTML-validate	The Nu Html Checker
Free Free to use, with the source code published on GitLab.	Free Free and open source under the MIT license.
Command line	Windows, macOS, Linux, Self-hosted, Command line
Validates entirely offline, so no markup is uploaded Handles HTML fragments inside Vue.js and AngularJS components	Checks HTML, CSS, and SVG Can run in scripts or as a self-hosted HTTP service
Command-line and tooling oriented, with no graphical interface Checks markup only, not CSS or accessibility in a browser	The portable JAR and WAR packages require Java 17 or later Deploying the WAR package requires a servlet container such as Tomcat
Downloadable app	Downloadable app, Self-hosted
Closed source	Open source
License not stated	License: MIT
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 8, 2026

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