W3 HTML validator warning Unable to Determine Parse Mode

Unable to Determine Parse Mode!
  • Direct Input mode, no MIME Media Type is served to the validator.
  • No known Document Type could be detected.
  • No XML declaration (e.g <?xml version="1.0"?>) could be found at the beginning of the document.
  • No XML namespace (e.g <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">) could be found at the root of the document.
  • As a default, the validator is falling back to SGML mode.

If you are trying to validate your HTML code using W3 validator (http://validator.w3.org/) and you are getting the above warning message, let's see how to resolve it

The reason you may be getting this warning is you have used tag without the document type (doctype) or the namespace.

<!DOCTYPE html>

<title>Some Page Title</title>

<p>This is my webpage</p>


Note that we have added!DOCTYPE in the HTML tag. This is not an HTML tag, it is used to tell the web browsers ( like Safari, Firefox, Mozilla, ie) what version of HTML you are using. !DOCTYPE tells the browser what your webpage adhere to HTML5 syntax.

If your website complies to HTML 4.01 Strict type then you must add the following namespace to your HTML tag,

&tl;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

If your website complies to HTML 4.01 Transitional type then you must add the following namespace to your HTML tag,

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

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