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How Does Google Treat Subdomains For SEO?

By August 1, 2018January 18th, 2024SEO, Technical SEO

Time and time again, Google has shown that they treat subdomains very differently from root domains, in some cases treating them as completely different sites. For SEO purposes, it’s generally recommended to use a subfolder instead of a subdomain.

Subdomain vs. Subfolder

A subdomain is a string of characters that precedes the root domain and uses a period to separate them. A subfolder comes after the domain suffix and is separated by a forward slash. You can have multiple subdomains or subfolders, and you’ll frequently see them combined.


  • is a subdomain
  • is a subfolder
  • is a subdomain with a subfolder.
  • is two subdomains (“first” and “blog”)
  • is two subdomains (“first” and “blog”) with two subfolders (“posts” and “recent”).

Did You Know?

In the URL, “www” is technically a subdomain. It’s true!

Why Use Subdomains?

There are legitimate reasons that necessitate the use of subdomains and subdomains are not completely unavoidable.

Technical Limitations

Sometimes there are technical infrastructure limitations that prevent the use of a subdomain. In large organizations with big sites, it’s common for access to the root domain to be limited, instead using subdomains for ease of use.

This may include piecing together multiple CMSs. If the core site is hosted on one CMS like Magento or Sitecore, but the blog is hosted on WordPress, it can be difficult (or impossible) to make them work together on the root domain.

Organizational Control

Large organizations often have multiple divisions that operate independently. Such is the case with universities, where individual colleges need to have edit access to their own sites (School of Nursing, School of Engineering, etc.). The same is true for other national organizations like banking institutions.

It’s a lot easier to spool up a separate site on a subdomain and grant a team of people edit access to that particular subdomain. You wouldn’t want the School of Nursing making edits that ended up taking down the entire root domain for the whole college.


Sometimes organizations will create international subdomains like or There’s no inherent SEO benefit to including a country code in the subdomain, but it may comeback to organizational structure or technical limitations. In a perfect world, you’d place those in subfolders ( or and implement hreflang. Alas, we  don’t live in a vacuum and that isn’t always possible.

How Google Treats Subdomains

Working with subdomain-heavy clients, my firsthand experience is that Google treats subdomains as separate sites. A client of mine who had two divisions of their company had one set up on subdomain and another on the root domain. They had some content overlap and we sometimes saw their pages swap places in search results.

It’s my belief that subdomains don’t inherit domain authority or site equity from the root domain. has a domain authority of 94. If subdomains inherited that value, wouldn’t it make sense to setup free blogs on their platform (which uses subdomains) and immediately benefit from the SEO value?

Secondly, Google’s own Search Console requires you to set up separate profiles for subdomains. That’s another good indicator that they value subdomains differently.

That doesn’t mean subdomains inherit ZERO equity from their root domains. They may inherit a greatly reduced amount. OR, Google may adjust the amount of equity they inherit on a case-by-case basis. Since has thousands of low-authority blogs on subdomains, Google may devalue their subdomains more than other sites that only have a handful.

Google has stated that their search engine is indifferent to subdomains vs. subfolders, but the SEO community has repeatedly found that to be false. Industry thought-leader Moz moved their content from a subdomain to a subfolder and saw measurable increases just as a result of that move.

Questions? Comments? Leave them here or reach out to me on Twitter: @BerkleyBikes.

Chris Berkley

Chris is a digital marketing consultant specializing in SEO and Analytics across industries including healthcare, education, finance and others.


  • GANESH says:


  • Jared says:

    You need to update this article. “CNN Coupons” is ranking very well, based on leeching off the authority of the domain. And what’s more JohnMu confirmed it’s fine, there’s nothing wrong with this nor the 100s of other European coupon sites whoring off the authority of the domain. As long as you can find an authority brand, subdomain leasing is fine. Confirmed:

    • Chris Berkley says:

      No, my logic stands. *may* inherit some amount of authority from the root domain (as indicated in the article), or it may rank well because it has thousands of quality backlinks from sites like Business Insider,, etc.

  • Jake says:

    Great article, Chris. I had the exact same logic in mind.

  • nice info, great article for seo, thanks christ

  • I have found a website running its subdomain and root domain they both have the same Alexa rank (164). when this subdomain was created it had got the same value as root domain had.

    And even now subdomain has more traffic.
    So I am just confused that how it got all SEO benefit from its root domain.

    • Chris Berkley says:

      A lot of tools that measure domain authority don’t differentiate between the root domain and the subdomain, so that may be the case with the Alexa rank.

  • Primoz says:

    If you are still not confused, according to Google itself it does not matter

    • Chris Berkley says:

      Yes, but field testing from numerous SEO experts has proved otherwise. And hard data beats talking points.

  • Suraj says:

    Really appreciate your work.

  • George says:

    Hi Chris, great article although I still have a couple of questions.

    1. If a subdomain is treated as a separate site would the sites be penalised for duplicate content?

    2. Some people seem to suggest that google reads sites as either transactional or educational. Does this mean that you should separate out a blog to a subdomain for instance on an e-commerce site?

    • Chris Berkley says:

      1. If it’s truly duplicate content, it’s bad either way. If it’s on the same domain, search engines will see it as spam and the likelihood of ranking is low. If it’s on different domains or subdomains, Google will see it as plagiarism and the likelihood of ranking is low.

      2. No, I would never advocate using a subdomain when it’s not necessary. There are plenty of sites that are both transactional AND educational that rank well for both types of queries. Part of being an eCommerce provider is informing visitors about the products you’re selling, so it’s never purely transactional.

  • Reading this, i guess it’s a bad idea to use a subdomain as homepage, no?

    • Chris Berkley says:

      Yes, assuming the rest of your site is not on the subdomain, I’d say having only the homepage on a subdomain is not recommended.

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