I'd like to compare the two sites:

Site A:

<!DOCTYPE html>
<html lang=en_US>

Site B:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en" dir="ltr">

The differences are:

  1. Site A doesn't have " for tag attributes.
  2. Site A has a very simple !DOCTYPE tag
  3. Site A has a very simple html tag

I'm wondering, are the three factors important for SEO rankings?

  • Outside of lang= defining the language there is no role for any of these tags.
    – closetnoc
    Jul 13, 2018 at 5:28
  • What do you mean? sorry I don't quite get it. Jul 13, 2018 at 5:29
  • 1
    SEO is not about tags. It is about content. Short of the lang= in the HTML tag defining the language of the page, these tags have absolutely nothing to do with SEO.
    – closetnoc
    Jul 13, 2018 at 5:38
  • Short of the lang= in the HTML tag defining the language of the page what do you mean by this“short of”? I'm still confused. Jul 13, 2018 at 5:50
  • The Doctype stuff that is there tells the browser how to read the HTML. You will typically see strict 1.0 ones used in email, due to emails clients. <!DOCTYPE html> is HTML 5. you can find out more on common doctypes at w3 schools w3schools.com/tags/tag_doctype.asp
    – Jason
    Jul 13, 2018 at 9:40

1 Answer 1


What you are asking is if HTML document type could affect SEO, right?. Based on my experience and logic I'll say no.

A site built to standards (valid HTML and CSS) is often easier to access and crawl by searchers but using different doctype will not boost your ranks cause accesibility it's not a direct SEO factor.

As long as you can check that Google renders your site correctly (without any error), nothing else in your code -from a tech point of view- should matter.

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