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Rocket Validator vs Nu Html Checker: catalog facts
Rocket Validator	Nu Html Checker
Paid Paid subscription service with a free trial.	Free Free to use on the W3C website.
Web	Web
Site-wide HTML and accessibility checks in one report Up to 5,000 pages per report	Checks against current HTML conformance rules rather than old doctypes Accepts a URL, a file upload or pasted markup
Paid service after the trial Requires an account	Checks one document at a time Behavior is described as experimental and subject to change
Hosted service	Web application
Closed source	Closed source
License not stated	License not stated
Account needed	No account needed
Needs internet	Needs internet
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 23, 2026

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