I am using the API validator.nu:
https://github.com/validator/validator/wiki/Service:-Input:-POST-body
I want to force validation according to strict or transitional XHTML doctype :
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
In the documentation, they are asking to send the request header: Content-type: text/html; charset=utf-8
I think that XHTML is a an XML-like code ?!
After sending the content which contains non-valid markup like <br> (no closing "/"), the web service doesn't return any errors. I think that is hanlding code as HTML5.
How to validate XHTML document ?