Subdomains and SEO, this is a hotly debated topic in webmaster and Search Engine Optimization (SEO) circles when you are setting up a new site or reconfiguring one for yourself, someone else, or a company or organization. Should you use subdomains or subdirectories? Do Google and other search engines treat them differently? Read on to find out the differences of subdomains vs subdirectories as seen through the eyes of someone that's actually built sites.
For those reading this that may not be sure what a subdomain is basically it would something like – news.AdamYamada.com – which might be a news portal separate from this site about internet marketing, SEO, and other web topics. (That subdomain will just forward here.)
Why would people use subdomains? Basically it allows for maximum flexibility when working with different types of content management systems and allows you to separate your site into different areas and make it clear for a visitor. Perhaps I might want to start a forum and use different web hosting than I'm currently using on my main site, AdamYamda.com. The forum could take more resources than a simple WordPress blog. By using a subdomain I could point – News.AdamYamada.com – subdomain to another web hosting company if needed.
Basically this just means that you install a content management system (CMS) or software into a folder on the domain you are already using. For instance – AdamYamada.com/blog – would be a subdirectory. Usually subdirectories are more popular than subdomains as the majority of CMS scripts support using subdirectories instead of subdomains. This site might be harder to navigate if all the URLs were subdomains.
Subdomains and SEO
Most webmasters will tell you subdomains will show up differently in SERPS (search engine results pages) and there is a big difference when building sites on subdomains. Google and other search engines tend to treat sites that are built with subdomains as different types of sites, even if that was not the webmasters original intention. Often it just works out that if you build a site using subdomains you'll have a hard time getting a search engine to think it's “Ok” to be that way.
This is why blogging services like Blogger, WordPress, Tumblr, etc. use subdomains instead of subdirectories when giving you a free URL. It doesn't usually pass pagerank or link juice your way and Google knows to treat that subdomain differently than a page.
Below is a explanation from Google's Matt Cutts about Subdomains and Subdirectories. As usual with Google advice it's not that clear but it's good to watch.
Subdomains and Subdirectories – Matt Cutts
I'm interested in finding out how Google currently views subdomains — whether there's any difference between a site structured as a group of subdomains and one structured as a group of subdirectories.
Bob, Somerville, MA
Have an opinion about subdomains and SEO? Let me know with a comment below.