Should you use subdomains or subdirectories?

I receieved an interesting question from one of my photographer friends Gustavo Fernandez today. “Why do some folk have their address as blog.domain.com vs domain.com/blog? Is there a benefit?”

I started to write back, but in doing a couple quick searches in the name of research, I found enough interesting information that I decided to write a post explaining it all.

Subdomains vs Subdirectories

photo credit: Tim Dorr

First, let’s define what we are talking about: “blog.domain.com” is a subdomain while “domain.com/blog” is a subdirectory or a folder within a domain.

A subdirectory is used as a folder within one domain to organize smaller pieces of content, like a category of several pages. For most people they will only ever need subdirectories.

A subdomain creates more separation than just a folder, basically creating a stand alone site that could easily be it’s own domain. However, you may want to piggyback on the main domain name. For example, google.com is the main site. Gmail actually lives at mail.google.com. Google Maps lives at maps.google.com, and Google Documents at docs.google.com. These are each stand alone sites and could be their own domains but they make more sense under the google umbrella.

On my own domain, I setup several subdomains to handle different aspects of my business. One contains all the temporary websites while I build them, including several installatons of wordpress and a few standard html sites that I use to test things on. This allows me to work on projects without making the under construction site visble on the client’s domain. Another subdomain was specifically setup to handle my project management. I use a system called ProjectPier, an open source project management app that allows me to share and store files, messages and task lists with an entire team and with the client. Each one of these subdomains is basically a site in and of itself. I want to keep everything within those subdomains separate from my main site.

So there are some different reasons at the hosing/server level for keeping your site organized. But as far as the url, it doesn’t make too much difference to me whether something like a blog lives at blog.domain.com or domain.com/blog.

How do subdomains effect SEO?

According to this article, subdomains used to help with SEO because there was a chance domain.com AND blog.domain.com would show up in results while there was (and is) a limit on two pages per domain in a search engine results page (SERP). You might see two pages from one site rank really high for books, but amazon is not going to take up the whole front page. However, setting up subdomains apparently used to trick the search into thinking it was looking at a new site so technically several subdomains could all end up on the front page, which would look really good. Of course, google is all about trying to provide relevant results, so a page of subdomains should no longer happen. For example if you are a national construction company that wants to get listed for each city, you might setup subdomains like losangeles.mycompany.com and boston.mycompany.com, then just copy your site over and over, swapping out the keywords and every mention of the city to match the the site. The problem is that there is no real interesting or different content on all these sites and in fact it is very obviousy duplicate content so the SEO effect is actually negative. Or you might try cellphones.myphonestore.com, mobilephones.myphonestore.com, and on and on hoping that all of these ‘sites’ might rank high, but the best result anywhere within “myphonestore.com” is all that would show up.

One strategy that could make sense would be to create a subdomain for a section of your business or site that could really be a standalone site. If you are a department store, you may have “mystore.com” and use “electronics.mystore.com” to create a site with great SEO specific to electronics, since the searches will see it essentially a stand alone site about electronics. Then use “food.mystore.com” to target searches specific to food. If you had those things combined (along with ten others – shoes, jewelry, etc. ) the content is not as specific and may be confusing as to what the site is about. Meanwhile, they all still help pump up the image of the main domain “mysite.com”. You have created several specific relevant sites all benefitting from the main brand of “mystore.com”.

Which one should I use?

For most situations and for the average website, the easiest solution is a new subdirectory. If you are setting up a new blog, you can create a folder called “blog” install wordpress and you have your blog at “mydomain.com/blog”. There is no reason to use a whole subdomain for that. I like the simple idea that if you could almost justify starting an entirely new (but related) site, then use a subdomain. If you are simply adding a new category of pages with similar content, then just use a subdirectory. Save the subdomain for something that is big enough and clearly separate enough that it needs to be its own site.

What is your experience with subdomains?

If anyone has a set-up using subdomains, why did you go that route? Do you see any benefit or negative effects of setting it up that way?