A previous post of mine Subdomains – Pros and Cons for SEO explained how search engines were seeing subdomains as a separate website to the naked domain.
This has some serious points for consideration when deciding whether to use a subdomain from an SEO perspective as any link juice from the root domain may not be shared onto the subdomain.
However a recent announcement by Google Webmaster blog has changed this strategy as now subdomains are regarded as internal links in Google Webmaster Tools.
So what does this mean?
Basically links from subdomains such as cats.example.com or pets.example.com will also be categorised as internal links for www.example.com.
|Links for www.google.com||External links||Internal links|
|Previously categorised as…||www.example.com/www.example.org/
|Now categorised as…||www.example.com/www.example.org/stuff.html||scholar.google.com/sketchup.google.com/
Large publishing networks such as ninemsn often use subdomains for different aspects of their site i.e. News, weather etc – linking from subdomains to other subdmains on their own network will have previously given authority as these subdomains were treated as separate websites but now this network linking will only contribute to each as an internal link.
For these large websites it is worth now considering external link building pratices outside of their network directly to the relevant subdomains to aid authority in each aspect of the site.
Note that, if you own a root domain like example.com or www.example.com, your number of external links may appear to go down with this change; this is because, as described above, some of the URLs we were previously classifying as external links will have moved into the internal links report. Your total number of links (internal + external) should not be affected by this change.