Recently, I’ve had to make a few decisions on whether to use subdomains or subdirectories for a site I will launch next year and was wondering how Google is handling subdomains in 2015 and how well they rank.

1 The Hubpage Case Study – Use Subdomains For User-Generated Content

Subdomains are great. They effectively tell Google this is a completely new site but is somewhat related to the main site IF we link to it.

Subdomains For User Generated Content

So what does is pretty clever: They create a new subdomain for each new user. Let’s take a look at the hubpage of Kevin Goodwin who writes about the top 5 goalkeepers playing today – this page is hosted on a subdomain

BUT when I take a look at the breadcrumbs I see a link to a category called Sports and Recreation:

When I visit the Hubpages Sports and Recreation category I will find a short intro of Kevin’s article. So, essentially is just a collection of user content where each user has its own subdomain. User-content is then listed in the “sports” category.

The sports category will have a lot of backlinks and therefore gain more weight via internal links.

But what if went ahead and moved all sports content to – would that hurt their rankings? Probably not, but it would stop giving users a sense of satisfaction.

When I create something for another website I may not only do it for the monetary incentive, but also for recognition. Having my name on a well established site means something. It means trust. Trust is a currency I can use on the internet.

In short: Hubpages uses subdomains for user-generated hubs. This will not necessarily yield a SEO-benefit and could actually hurt their rankings, but it does give users another incentive to publish.

2 The Case Study: Subdomains For Categories

Now unlike, is not using subdomains for user-generated content, instead they use it for very distinct categories like auto, culture, entertainment, health, lifestyle, money, science, tech and so on.

How Stuff Works Subdomains For Categories

This setup makes a lot of sense for very large sites with many editors (newspapers etc). If you have a lot of editors and a lot of content to deal with it makes perfect sense to create sub-divisions and use subdomains to differentiate between the different topics.

Articles in the animal category have little in common with articles in the electronics category, so anything that is not relevant can be excluded from all pages on the animal subdomain, that’s great for SEO because you can create highly relevant content hubs.

That this is not always a good idea shows us the last example.

3 The Wrong Way: Subdomains For Highly Relevant Content On Authority Domains co-founder Rand Fishkin disclosed that they incorrectly used a subdomain for their SEO guides using the subdomain in 2011/2012. When Moz moved the content from to it went from position #7 to position #1 in Google’s listings.

Moving From Subdomain To Subdirectory.png

What’s interesting here is that is basically a subdomain for highly relevant content. Let’s imagine had also written a guide about “dog training”, published it at and then eventually moved the content to – do you think the result would have been the same? I doubt it. received a lot of valuable inbound links from all sorts of marketing sites. Those links give authority in the SEO and marketing community but not a great deal of authority in the dog training business. So it only makes sense that this specific article ranks so well now.

In a nutshell: Highly relevant content should never be put on subdomains because the main domain receives the most inbound-links and will generally outperform subdomains within search engines.

4 Use Subdomains For A Higher Adwords Quality Score

The last case study is for Adwords users. Subdomains are a great way to increase your quality score.

Let’s say you own and you have a 100,000 USD budget to promote your new “office supplies” via Adwords. What would you do now? If you’re lazy you’d just copy some of your restaurant supply pages and the template and use the same structure e.g.

After studying a few ads, you may be wondering why are so many marketing agencies using subdomains in such a case? The answer is simple. Adwords only shows a certain number of characters and exact matches that start with the keyword usually perform better. So if you create a subdomain at your domain e.g. you can create a highly relevant promotional page that will decrease your advertising costs (in theory) by increasing your click rate.

Always keep in mind, we usually scan text from left to right so the bold part (the matched keyword) should appear first to allow for easier scanning. 

Especially brands that are not well established may want to use subdomains for their promotional Adwords campaign. It looks nicer and will often increase your CTR (click-through rate).

In A Nutshell:

  • 1 Use subdomains for user-generated content
  • 2 Use subdomains for large content sites with many different topics
  • 3 NEVER use subdomains for highly relevant content on an authority domain
  • 4 Use subdomains to increase your Adwords CTR
  • 5 Still unsure? Go with subdirectories.