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

One of the heated debates I was involved in was whether or not Taylor Swift is a good dancer.

The first thing you should know about me is that Taylor Swift is my favorite artist. So you have a hard time convincing me that she is bad at everything (because she is not).

SEO pros likely do the same when discussing whether subdomains or subdirectories are better for SEO. As a marketer, this debate can lead to confusion and analytical paralysis.

In this article, you will learn the differences between a subdomain and a subdirectory and how they affect SEO. Both have advantages and disadvantages, and you should consider all of these factors before proceeding with your website project.

Subdirectory url

In a URL, the subdirectory comes after the root directory or domain name. For example, HubSpot’s root domain is hubspot.com. So a subdirectory URL could be hubspot.com/pricing. Or it could be a little more complicated, like hubspot.com/pricing/sales. Below is an illustration of one possible subtree structure.

When it comes to subdirectories, think of a structure similar to that of nested dolls. Each folder can build on one another almost indefinitely. That means you can have a subfolder within a subfolder within a subfolder until it is dozens, possibly hundreds, of levels deep.

But just because you can doesn’t mean you should.

Too many levels of sub-folders can turn into an SEO nightmare. The URL string will get long and confusing, the user experience will be compromised with every click it takes to get to the next piece of content, and search engine crawlers will find it almost impossible to crawl your website for new content and other SEO gains to achieve that you’ve possibly added.

On the flip side, subfolders can be great for SEO as they keep all of the backlinks, domain authority, and page authority earned closely tied to the root domain. And if the website is relatively easy to navigate, the URLs are short and simple, like hubspot.com/careers, which means you can market specific webpages or landing pages based on their URL without confusing your audience.

The structure of a subdomain is pretty flat at the top levels. You have your root directory, then all of the subdomains below it in a horizontal row. All subdomains are on the same level. You don’t have a subdomain within a subdomain like a subfolder within a subfolder.

SEO and subdomains

A subdomain can be great for SEO, but it does require a dedicated person or team to manage it. Unlike subdirectories, the domain authority of a subdomain is not automatically trickled down from the primary domain name. You may also pay extra for tools or subscriptions if you’re billed per domain name, as each subdomain usually counts as a separate website. Given these challenges, let’s take a closer look at the benefits of using a subdomain.

Why use subdomains?

Subdomains are ideal if your business contains a lot of content that would be difficult to manage on a website. This structure can also be useful if you have several large recurring campaigns that need separate landing pages, or if you are planning to partner with another organization and want to split up the branding of the project.

In short, subdomains make sense when you have a relevant business need to separate content on your website.

There are a number of times a company should use a subdomain. Below are the most common.

1. Support

Sometimes it doesn’t make sense to have your customer support on your main page. For example, Google uses support.google.com instead of google.com/support. The main reason is likely due to the site structure. Google.com is a search engine, and Google’s support line is not part of its search line of business. Hence, it needs its own subdomain to properly connect to and serve its users.

2. Different regions

If you serve multiple regions on a national or international level, using a subdomain is a good idea. If you had a site in German and one in English, it wouldn’t make sense to list them as subdirectories. For example, Craigslist uses subdomains for the different regions it serves. Here are two of his subdomain sites: orangecounty.craigslist.org/ or stgeorge.craigslist.org/.

3. Blog

Many companies choose to have their blog as a subdomain. That is exactly what HubSpot does. When you notice that the page you are currently on is a blog.hubspot.com page. However, that particular article is located in the Marketing subdirectory of the blog.hubspot.com subdomain. Websites can use their blog as a subdomain if they have a content campaign big enough to deserve their own hierarchy and growth path (more on that in a minute). Additionally, a subdomain for a blog is useful if you want to build a niche authority.

4. Ecommerce store

For companies that sell goods, they can place their e-commerce shop on a subdomain in addition to their regular products or services. HubSpot does this too. Aside from our main software hubs, HubSpot merchandise is available at shop.hubspot.com.

5. Events

If your business is hosting events, it might be a good idea to divide this section of your website into a subdomain. Again, this is helpful when you want to differentiate a section of your website from your regular product or service. Microsoft does this with its events.microsoft.com.

Technically, a website can use both a subdomain and a subtree structure. Subdomains usually contain at least a few subfolders to organize content, but probably not as many as a subdirectory. This is because a subdomain has a smaller variety of content than a root domain with subfolders.

Hence, it is important to understand what the primary structure of your website will look like. To decide that, let’s take a closer look at how subdomains and subdirectories affect SEO.

How do subdomains and subdirectories affect SEO?

Some SEO experts believe that Google’s crawlers could mistake a subdomain for a completely different website from the main domain. However, others say that its crawlers can recognize subdomains as extensions of parent domains.

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

In the video below, Google Webmasters Trends analyst John Mueller says that subdomains generally don’t affect a website’s ranking. In fact, he says that Google is smart enough to see that your main domain and subdomain are linked to the same website.

Some SEO experts argue that subdomains don’t share the authority they get from inbound links (or backlinks) with the root domain. The opposite can also be the case; Since subdomains are seen as separate entities from your root domain, they may not inherit any of the link authorities that you have already created for your core website content.

Also, if you optimize pages for the same keywords on your main website and subdomain, you could be competing with yourself.

On the other hand, other SEO experts argue that subdomains make it easier to navigate your website. Ultimately, this leads to a better user experience, which can lead to better engagement rates and thus improve your SEO.

Subdomains can be beneficial if you have a large company and the subdomains are for a different purpose and essentially act 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 have the same authority on backlinks as they are unlikely to target the same keywords.

Another benefit, according to some SEO experts, is that subdomains can help in building niche authority. For example, you might want your blog to be seen as a separate entity from your product or service.

Conversely, if your website doesn’t have extensive branches in your navigation, you may not need to use a subdomain as you want as many links as possible to lead back to your main website. Unless you have a compelling reason to use subdomains, then subdirectories work fine.

Which is better: subdirectory or subdomain?

While this topic can often be confusing, the decision ultimately depends on the needs of your website. Subdomains can add organization and structure to your site when you want to share a lot of different but important content. Subdirectories can be useful for smaller websites that don’t have a wide variety of content. Whichever structure you choose, you should stay current with the best SEO practices to meet your website goals. The free guide below will help you improve your website with a free SEO audit toolkit.

Editor’s note: This post was originally published in February 2020 and has been updated for completeness.