There have been many debates between search engine optimization experts on the value of subdomains vs. directory structure. But as a result of the new update to the way internal links are viewed from subdomains in webmaster tools, this conversation may drastically change.
Background on Internal Links from Sudomains
Prior to this update, links from subdomains to the parent website were seen as external links. The parent website would be regarded as the site specified in webmaster tools as the main site. So for example, if www.seoinc.com were listed in a webmaster tools account and links from a subdomain, such as (this does not exist so don’t go thereJ) would be seen as an external link. This is very important for SEO because subdomains need to be treated as their own site. They need their own sitemaps, robots.txt files, webmaster tools accounts and maybe most importantly, Google sees the pages on these subdomains as only being more loosely affiliated with the main site. It is for this exact reason that we always recommend blogs be built at www.example.com/blog opposed to blog.example.com. Furthermore, we only recommend subdomains if there is enough content to support basically another site, SEO campaign or if there is something very location specific, sometimes it makes sense.
How Linking from Subdomains has Changed in Webmaster Tools
Google has recently come to the conclusion that links from subdomains to the main website should be viewed in webmaster tools as internal links, not links from another website.
“Most people think of example.com and www.example.com as the same site these days, so we’re changing it such that now, if you add either example.com or www.example.com as a site, links from both the www and non-www versions of the domain will be categorized as internal links. We’ve also extended this idea to include other subdomains, since many people who own a domain also own its subdomains—so links from cats.example.com or pets.example.com will also be categorized as internal links for www.example.com.” Said Google.
The million dollar question is, how will this change affect SEO? Unfortunately, this has not been commented on by Google at this point. While this is the case, we can speculate that if sudomains are now being viewed as part of the main site, we would expect that the content on these subdomains may now be attributed more closely to the parent site. However, only time will tell if this is true. Now when we inspect the issue of link weight, it would seem that it would remain consistent with the basic principals of SEO. Whether it is internal of external, essentially, links from pages with authority and trends ranking for comparable keywords will continue to support SEO for the pages they link to.
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