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W3C Validator is dead, long live!

by Jaime Iniesta

It may not be apparent, but the W3C HTML Validator that we've been using all these years, yes, the one at, is dead.

Well, at least as dead as a software service can be. For a time, its official repo was called legacy-markup-validator and, although now the repo is back to its original name, still it has a very low activity, mostly docs and readme fixes.

Under the hood, a faster, more modern and more robust validator has been in charge of validating HTML5 web pages. Its name is but now it doesn't like to be called that way, and prefers to be called Nu HTML Checker. And yes, it lives within the W3C domains, you'll find it at

A Nu Hope

Nu HTML Checker screenshot

The Nu HTML Checker is being actively maintained, with new releases coming out frequently.

On the W3C, Mike[tm] Smith (AKA @sideshowbarker) is the maintainer of and he's recently been interviewed at HTML5 Doctor about the change to, you should definitely check out the interview to understand the direction that the W3C is taking in validation markup checking.

Here at Rocket Validator, we're commited to giving you the most up-to-date markup checking tools, and that's why we've dropped the legacy markup validator and installed exclusively.

To do that, we're actively contributing to open source, helping on the installation of new instances via Docker images, and developing clients to query the instances.

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