The W3C announced the release of an API for the HTML validator or rather, that’s what they call it. In fact, it’s nothing more than an output filter on their normal validator output, which gives SOAP 1.2 conforming output. It requires a HTTP request though, which makes it a rather funny “API” to deal with.
I created a simple implementation on top of it, using PHP’s DOMDocument extension to walk through the result, as using NUSoap or something like that felt like overkill, and it would be hard since the request isn’t a SOAP request. It’s quite simple, but it’s also slow…
So, my wishlist for the next version of this API:
a way to do a SOAP request instead of a HTTP request;
faster, please, please W3C, make it faster;
a way to specify what info i want, it would be cool to be able to just know if a site is valid or not.
February 18, 2026
Team Yoast is Speaking at The Stage - WP SEO Panel: The current state of WordPress SEO! Click through to see who will be there, what we will do, and more!
See where you can find us next
19 February 2026
Discover how to effectively use the Yoast SEO plugin. Get hands-on tips for setup, content optimization, and more.
All Yoast SEO Webinars
Discussion (21)