I’m looking for a hosted Web app that validates HTML5 documents.

The tool must be able to check the document for conformance to the HTML5 W3C Recommendation from 2014-10-28. That means, for example, that it should report an error for a document that uses a picture element (as it’s not part of W3C’s HTML5 Rec).

Checking conformance to W3C’s HTML 5.1 and to WHATWG’s HTML is not required, but would be nice to have in addition.

Pasting the document is preferred, but checking via URL or by uploading a file would be okay, too.

Support for extensions (like Microdata, RDFa, …) would be great, but it’s not required.

What I’ve tried:

  • 1
    How do each of the listed services not meet your requirements? What prompted you to post this Question? You must make your criteria clear to provoke good answers. As far as I know validator.w3.org does the job you asked for. Jul 26, 2015 at 4:30
  • 2
    @BasilBourque: It’s in the second sentence, with the bolded "must": I need a conformance checker for the HTML5 W3C Recommendation, which, for example, doesn’t define a picture element (so the checker must report an error if picture is used). -- As also explained in the question (first bullet point), validator.w3.org redirects to the Nu validator if you want to check HTML5.
    – unor
    Jul 26, 2015 at 12:08


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