Polyglot-Markup validator

Question

Is there a free online polyglot-markup validation service that will correctly identify and validate polyglot-markup?

I did find totalvalidator and htmlvalidator but those are (paid) non-web-based solutions.

Answer 1

Use http://validator.w3.org/nu/ and use “Options” to select first HTML5 (= HTML5 in HTML serialization) parsing mode, then XML parsing mode.