Why Subdomains Are Not Bad for SEO
One of the biggest pitfalls of adhering to so-called “SEO best practices” is that human beings are creatures of habit. As such, we cling to ideas that have been relevant to us based on personal experience, sometimes in the face of all logic (just look at all of the websites still using the keyword meta tag if you don’t believe me). Even though the hard evidence has always been a bit murky, many people who do SEO have traditionally preached that subdomains are undesirable, especially when compared to sub folders. Like so many things SEO, the reality is much more complicated than a simple yes or no. There have always been very good reasons to choose subdomains, and more and more it seems that they can actually be a boon to SEO when used properly.
Now, for those of you who don’t live and breathe this stuff, here’s the Reader’s Digest version of what a subdomain is. Essentially, a subdomain is a prefix to a website domain. For example, google.com is a domain. Something like mail.google.com is a subdomain of google.com (the “mail” being the subdomain in that case). A sub folder is a similar concept, but it manifests itself as a directory of a domain. A good example of this would be mattcutts.com/blog.
For a while now, traditional SEO wisdom has said that subdomains are viewed as entirely different domains and therefore don’t carry the weight of the top level domain. By that logic, it’s always better to use sub folders, because the search engines will view that content as part of the top level domain and transfer all of the authority that goes with that domain to that new content. Not so fast.
We use subdomains for lots of things at DAC, and this objection comes up a lot with clients who have heard or read that subdomains are a bad idea for SEO. The fact is that subdomains are very often a great way to segment different types of content, and we have consistently seen excellent results for entire web properties when we use them. Here’s just one example (and there are many more) of the lift we saw when we added some scaled local content to a client’s site on a subdomain:
As you can see, the creation of the subdomain with the new content significantly enhanced the overall organic traction of the site by adding incremental traffic to the subdomain while organic traffic to the top level domain continued to grow.
Other very big content providers like Wikipedia, About.com and countless others have been successfully using them for years to segment content. Further, there have been a number of recent developments that seem to suggest that the proper use of subdomains is, in fact, a very good idea. Just recently, Google Webmaster Tools announced that it would be viewing links from subdomains as internal rather than external links. There have also been accounts that HubPages successfully used subdomains to segment content at the recommendation of Matt Cutts himself in order to overcome the huge SEO beating they took from the Panda update. Cutts, for his part, tried to speak some order into the subdomain debate chaos (albeit in his characteristically noncommittal way) all the way back in 2007.
So, what does all of this really mean? The very simple answer is that subdomains are not “bad” for SEO. Should you put every section of your site onto a separate subdomain? Probably not. But if you want to segment some content, optimize it for SEO and conversion and perhaps in doing so differentiate the look and feel of that content from the standard look and feel of your site, subdomains can be a very effective way to do those things. Here are some examples of content that could logically be hosted on subdomains:
- Location-specific content for brands with large geographic footprints
- International content for companies who want to market to various countries (perhaps in various languages)
- Content about specific product lines or services
- Blogs or news content
- Content about related brands or specializations
This is a very short sampling of a long list of possible uses for subdomains. There are certainly no hard and fast rules for what content should be hosted on a subdomain, but each case should be closely evaluated and then measured for performance against objectives. The biggest mistake you can make is shying away from subdomains in a wholesale fashion because of some vague notion that they are “bad” for SEO. They are not.
Here are some additional resources that might help you make the determination of whether or not to use a subdomain:
- Rand Fishkin from SEOmoz discusses implications for international SEO
- Michael Martinez takes a deep dive into the question at SEO Theory
- Vanessa Fox talks about host crowding way back in 2007