An SEJ Reader send in the following question :
Subdomains or Subfolders? What’s better for a blog/forum/etc: a subdomain (eg. http://jobs.searchenginejournal.com/) or subfolder (eg. http://www.seomoz.org/blog/)?
Subdomains and subfolders both have their advantages, especially when setting up blogs.
For blogs, I prefer a subfolder (http://www.seomoz.org/blog/) because the link juice which is sent to that blog is going to be naturally distributed to that main domain, and other subfolders under the domain.
Futhermore, the forum/blog will default logo, home page and other links back to the subfolder. If you set this up with a subdomain, by default, the links in the forum/blog itself will all point back to the subdomain. So, with a subfolder, both the inbound and internal linking structure favor the entire site.
With a subdomain, the forum or blog will be listed as a separate entity in the Google search results, which is good for owning the results and one’s reputation management. However, Google and other engines will generally not list more than two of these subdomains in the search results, unless those subdomains can prove to Google that they are independent and relevant entities.
I would like to reference Vanessa Fox, an ex-Googler and contributor to Search Engine Land :
Google is no longer treating subdomains (blog.widgets.com versus widgets.com) independently, instead attaching some association between them. The ranking algorithms have been tweaked so that pages from multiple subdomains have a much higher relevance bar to clear in order to be shown.
It’s not that the “two page limit” now means from any domain and its associated subdomains in total. It’s simply a bit harder than it used to be for multiple subdomains to rank in a set of 10 results. If multiple subdomains are highly relevant for a query, it’s still possible for all of them to rank well.
Home Depot is one site which has cleared the relevancy bar at Google with subdomains at HomeDepot.com that are actually marketed as individual sites. Take careers.homedepot.com and look into its backlinks, even if this subdomain was on a whole different domain, like HomeDepotJobs.com, it would probably rank just as highly.
So, in conclusion, if you’d like to build the equity of one web site or entity, I suggest using a subfolder. If you’d like to build an entire new entity with its own equity, launch a subdomain.
Your thoughts, comments and concerns are well appreciated.