The subdomain vs subdirectory question is one of many you have to ask when optimising or building a site. As with most things SEO, there are differing opinions on how search engines differentiate between subdomains and subdirectories (or subfolders). It's important to figure out which is best for you, as the choice of domain can have a significant effect on your rankings.
After a good few hours of research and even a few comments from Matt Cutts himself on this subject matter, I found good points for both sides of the subdomain vs subdirectory conundrum. It’s all about how you want your website to be targeted by the search engines and Internet users alike.
This is going to have to be a 2 part post as it is jolly long! Today's post is going to concentrate on subdomains.
What Are They?
Wikipedia defines a subdomain in the following way:
"In the Domain Name System (DNS) hierarchy, a subdomain is a domain that is part of a larger domain."
A subdomain could be on a different server. A subdirectory, on the other hand, is a folder on the same server. In simpler terms, you can recognise the difference between subdomains and subdirectories when you see them.
Subdomains typically come in the format bonsai.smalltrees.com, while subdirectories look like this: smalltrees.com/bonsai.
When You Should Use Subdomains Over Subdirectories
A main point to remember about when to use subdomains is that these should only be used when you have enough unique content to create a whole website dedicated to one theme. With subdirectories they are generally only one page, targeting a few specific keywords.
Subdomains are a great option if you have enough original content to constitute another site. (Image credit: 10ch)
Use subdomains when your base idea corresponds with these other equally important pointers:
- You want to keep your brand awareness by using the root domain name in the URL but want to categorise your site more. Or in easier terms – if you want to brand your different niches.
- Targeting specific keywords in your URL is something you would like to concentrate on and those keywords are not already in the root domain. This is easier to do when there is a theme instead of just a bunch of keywords that you want to target – one of the subdomain best practises (eg: expanding the smalltrees.com business to include a stand-alone Bonsai section – bonsai.smalltrees.com).
- Tracking is important for site analysis. It is easier to monitor specific traffic on different sites than on a single site. This is where the ability to go into depth on each subdomain comes into play – something you won't be able to do as easily on a site that has a lot of subdirectories. The tracking and analysis is more targeted.
- Targeting different languages or geo locations is important to you. e.g. Iowa.Cats.com, Germany.Cats.com, English.CanadianCats.com or French.CanadianCats.com.
Things You Need to Know About Subdomains
In General
- Subdomains may benefit from the root domain they are sitting on, this means that they may inherit the positive metrics that a root domain has, such as ranking potential, but it also means it may inherit bad metrics, such as any kind of penalities the root has suffered.
- It is possible to add subdirectories to your subdomain e.g. cats.dogs.com/raining.
- There is a limit to the amount of subdomains that you can create. That depends on your host so you will have to check with them.
Search Engine Submissions
- Submissions of multiple subdomains to search directories is possible because they all have a different focus and unique content (well they should have). The most important thing to keep in mind with this is not to create too many or you may suffer from a spam penalty or the sites will be banned. As long as your content is all unique to its theme you should be safe.
- It may take a while for these sites to be indexed by search engines as they are seen as new websites. This is more commonly known as the sandbox issue and most new websites go through it at least to some degree.
Content
- The content is more important than the structure. Think of the alt tags, title tags and meta tags. They all need to be different yet relevant.
Costs and Time
- Costs may be eliminated by using subdomains. Instead of creating a whole new domain you can create multiple subdomains for free – but again check with your host as some charge for more subdomians.
- It may be time consuming to store a bunch of subdomains because they are (should be) set up as whole new websites. The content and images will be stored and edited separately. Each sub should also have its own FTP server and directory structure. Think of the maintenance needed. Keep this is mind when deciding whether or not to use subdomains.
IP Address
- Check with your host as well that your subdomains are sharing IP addresses with legitimate sites or they could be penalised. Even though they are independent sites, they share IP addresses with your root domain and any other subdomains that you have because they are hosted on a virtual hosting platform instead of its own server.
- If all of your subdomains are hosted on the same IP address, there is more of a chance of them being seen as one website by search engines.
One thing you need to remember though is that Google specifically is better at “deciding” which subdomains deserve rankings and which ones don't. It’s all up to your content. If the subs are too similar in content, they may not be ranked. Worse, if they have duplicate content, you could be shooting yourself in the foot, weakening your potential to rank well on the SERPs.
The final point to remember? Test, test and test again. That's the only way you will learn what works for you best. You know what they say..what's good for the goose ISN'T always good for the gander. I'd love to hear what your experience has been.
What about an in depth look at subdirectories you say? Well now, you will have to wait for that one until next week.
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*Update You can see Part 2 here.
Did you find this post interesting? Why not check out:
We are in the process of redesigning our entire website and are going to be dedicating subdomains to some of our individual products. Here's to holding thumbs...
Posted by Adrian on 2009/05/14