Subdomain or Subdirectory? What They Are & How They Affect SEO

One of the most heated debates that I’ve been apart of is when I was arguing with my best friend that Taylor Swift is a good dancer.

The first thing you should know about me is that Taylor Swift is my favorite artist, so you’d have a hard time convincing me she’s bad at anything (because she isn’t).

That’s how I imagine the debate is between two search engine optimizers who debate whether subdomains or subdirectories are better for SEO.

As a marketer, that debate can cause confusion.

Below, let’s review the differences between a subdomain and subdirectory and how they affect SEO.

Essentially, it’s all about site hierarchy.

Subdomains appear before the domain name in a URL, such as blog.hubspot.com, instead of a subdirectory, which would look like this: hubspot.com/blog.

A subdomain can be used if portions of your site are extensive enough that they need a separate hierarchy. When it comes to a subdirectory, though, all portions of your site branch off of the main domain.

So, how can a company use a subdomain? Below are the most common ways:

1. Support: Sometimes it doesn’t make sense to have your customer support on your main site. For instance, Google uses support.google.com instead of google.com/support. The main reason is probably because of the site structure. Google.com is a search engine, and Google’s Support line doesn’t belong to its Search business line. Therefore, it needs its own subdomain to properly connect with and serve its users.

2. Different Regions: If you serve multiple regions, whether nationally or internationally, using a subdomain would be a good idea. If you had a site in German and one in English, it wouldn’t make sense to list those as subdirectories. For instance, Craigslist uses subdomains for the different regions it serves. Here are two of its subdomain sites: orangecounty.craigslist.org/ or stgeorge.craigslist.org/.

3. Blog: Many companies choose to have their blog as a subdomain. In fact, that’s what HubSpot does. If you’ll notice, the page you’re on right now is a blog.hubspot.com page. However, this specific article is in the Marketing subdirectory of the blog.hubspot.com subdomain. Sites may choose to have their blog as a subdomain if they have a content campaign in mind that’s large enough in volume to deserve its own hierarchy and growth path (more on that in a minute). Additionally, a subdomain is useful for a blog if you want to create a niche authority.

4. Ecommerce Store: For companies that sell merchandise, in addition to their regular product or service, they can put their ecommerce store on a subdomain. For instance, that’s what HubSpot does. Aside from our main software hubs, HubSpot merchandise is available at shop.hubspot.com.

5. Events: If your company hosts events, it might be a good idea to partition that section of your site into a subdomain. Again, this is helpful when you want to distinguish a section of your site from your regular product or service. Microsoft does this with its events.microsoft.com.

Ultimately, subdomains are still a part of a website, but when a search engine goes to index those pages, they’re considered a separate entity. Below, let’s dive into how these affect SEO.

How do Subdomains and Subdirectories Affect SEO?

Some SEO experts believe that Google’s crawlers could confuse a subdomain for an entirely different website from the main domain. However, Google says its crawlers can recognize subdomains as extensions of parent domains.

According to Google, the site crawls, indexes, and ranks subdomains and subdirectories the same way.

In the video below, Google Webmasters Trends Analyst John Mueller says, subdomains generally don’t hurt a site’s rankings. In fact, he says Google is smart enough to see your main domain and subdomain as being tied to the same website.

Some SEO professionals argue that subdomains don’t share the authority it receives from inbound links (or backlinks) with the root domain. The reverse can also be true; because subdomains are considered separate entities from your root domain, it may not inherit any of the link authority you’ve already built to your core website content.

Additionally, if you’re optimizing pages for the same keywords on your main site and subdomain, you could be competing against yourself.

On the other hand, other SEO experts argue that subdomains make it easier to navigate your site. Ultimately, this leads to a better user experience, which could result in better engagement rates, therefore improving your SEO.

Additionally, subdomains can be beneficial if you have a large corporation and the subdomains serve a different purpose and essentially function as a separate business.

For example, Disney has subdomains such as cars.disney.com, shop.disney.com, and movies.disney.com.

Since these subdomains serve very different purposes, it doesn’t matter if the sites don’t share the same authority from backlinks, because they probably aren’t targeting the same keywords.

According to some SEO experts, another benefit is that subdomains can help build niche authority. For instance, you might want your blog to be considered a separate entity from your product or service.

Conversely, if your site doesn’t have any extensive verticals on your navigation, then you might not need to use a subdomain because you want as many links going back to your main site as possible. If you don’t have a compelling reason to use subdomains, then subdirectories work just fine.

Although this topic can often be confusing, ultimately the decision depends on your website’s needs. Subdomains can provide organization and structure to your site for complicated site hierarchies. If you don’t have the need, then using a subdirectory can help bring all the “link juice” to your main domain.