When it comes to search engine optimization (SEO), there’s bound to be disagreement – the complexity of search engines and their algorithms all but guarantee it. Different people interpret data in different ways, and this leads to different responses.
One of the biggest debates in SEO at the moment is between the use of subdomains and subdirectories to organize your website’s hierarchy. In this guide, we’ll be giving you all the information you need to decide for yourself.
Subdomain vs. Subdirectory: Summary
According to Google, subdomains and subdirectories are seen as equal when it comes to indexing and ranking. That said, real-world case studies show that subdirectories tend to rank faster and more effectively than subdomains on the first page of the search engine results page (SERPs).
What is a subdomain?
A subdomain is like a domain extension or alternative name for a site that lives under the same domain as your main site. An example of this can be seen on many e-commerce websites which have their shop or marketplace located at a separate URL from their normal website. In these cases, the shop or marketplace URL ends up being a subdomain, such as:
A subdomain is another domain, or top-level domain (TLD), that exists within the main site. If you have a blog on WordPress, for instance, it’s sometimes located at an address like this:
In this example, blog is the subdomain to .example – the main domain of the URL.
Why Would You Use A Subdomain?
In practice, subdomains are typically used to create _logical distinctions _between two related web resources. What’s determines a logical distinction? That’s largely a matter of personal choice.
There is a number of reasons that a business might decide to segment one part of its operations from another through the use of a subdomain. While we can’t list them all, here are a few common reasons that subdomains get used.
One common use of subdomains is in sites where the content is too diverse to be contained under the main domain. Take the New York Times, for example. They operate the main domain at nytimes.com for all the news articles and profiles you’d expect to find on the New York Times’ website.
However, they also operate a subdomain at cooking.nytimes.com where you can find all the delicious recipes they feature in the paper.
Someone at the New York Times decided that recipes were far enough removed from their standard content that they warranted the creation of a dedicated subdomain to organize them.
A subdomain structure can also help in situations where different parts of your website need markedly different branding than you typically use.
Subdomains are essentially distinct sites. That means that you’re free to change up the look and feel of the site without changing anything on your main site.
Going back to the New York Times example, there are some pretty clear differences between the main site and the cooking subdomain site.
New York Times:
New York Times Cooking
Sometimes, businesses choose to use subdomains for the simple fact that they need to limit the complexity of their website hierarchies. According to Kissmetrics, keeping the number of website directories between two and seven is ideal for organization and content crawling, and using subdomains is a viable way to achieve this.
Take Google, for example. The insane variety and complexity of the services Google offers means that using subdomains is a powerful organizational tool in their arsenal – which they frequently use. Here are some examples:
- drive.google.com – Google’s cloud storage service
- mail.google.com – Google’s mail service
- support.google.com – Google’s support information and documentation
If Google tried to organize each of these services under a single, main domain, the complexity of the site hierarchy would make it almost impossible to troubleshoot or manage.
Many start-ups are choosing to host a landing page for their product at a root domain and the product itself at a subdomain. For example, one of our clients, Flick, uses a subdomain for their SaaS app:
- Flick.tech – Here, they house their homepage, sales-focused landing pages, and blog subdirectory.
- App.flick.tech – Flick’s Instagram hashtag manager and analytics tool.
What is a subdirectory?
A subdirectory, or subfolder, is a directory that exists inside another directory. For instance, you might have the main directory www.example.com. Within that main directory, you might have the subdirectory /blog. Shown with the main directory, it would look like:
Subdirectories are subsets of pages on your main website. They’re essentially just subsections of your website that exist at their unique URLs within your site. For example, if you had a large e-commerce store with three top-level navigation categories – clothing, home improvement and automotive parts – you might create corresponding subdirectories for each type of product: /apparel, /homeimprovement, and /automotive.
Why Would You Use A Subdirectory?
Focus on one single domain
Managing several different domains and subdomains can be a tedious exercise. Not only do you have to make sure that the subdomains look different from one another to avoid confusion, but you also need to regularly update all of them with fresh content. Subdirectories are perfect for startups that don’t produce different types of content and need to focus on agility and execution.
Easier website tracking
If you’re using Google Analytics, you won’t need to go through different websites using subfolders, as all the pages are located under one root domain. This can allow you to save time and energy when tracking your website traffic and conversions.
Finally, using subfolders provides a streamlined approach to online content creation. This can be beneficial for startups that do not have to produce very different types of content or web pages. At the same time, it can also be easier to update the website with fresh content, as we’ve mentioned before. As we will explore in the next sections, a regularly updated website with a strong internal linking structure is important for SEO, and can help your domain rank faster.
Which Does Google Prefer?
Search engines are constantly evolving. That makes it pretty difficult to determine the various nuances of their ranking algorithms with 100% certainty. Not to mention the fact that many search engines consider a huge variety of different ranking factors when it comes to indexing a webpage.
According to Google itself, both subdomains and subcategories are seen as equal in the eyes of its indexing and content crawling algorithms. You can hear it straight from the horse (in this case, John Mueller’s) mouth in this episode of Google’s SEO Snippets.
Theoretically, that means Google should give equal index rank blog.example.com and* example.com/blog*. That’s great news from an SEO perspective as it allows for personal preference to be the main determinant in the subdomain – subdirectory debate…. right?
Well, maybe not. Data from the SEO trenches show seems to contradict the official line from Google across the board. Here are three cases that tell a vastly different story:
International payment service World First released data from an experiment they conducted on the respective indexing power of subdomains and subdirectories. The setup was simple: they moved their blog from blog.worldfirst.com _to _worldfirst.com/blog.
While the specific growth figures aren’t included for privacy reasons, the change resulted in a ton of new organic traffic to the site as you can see from the handy graph they posted.
HotPads is a map-based rentals marketplace that – like World First – used to publish its blog to a subdomain. The site was reorganized and the blog was moved from blog.hotpads.com to a subdirectory on the main site: hotpads.com/blog. The organic traffic growth that resulted – represented by the chart below – is pretty striking.
IWantMyName is a domain registrar that uses a blog to drive organic traffic to its site. Back in 2014, they ran the opposite experiment as the businesses above. Instead of moving their blog from a subdomain to a subdirectory, they moved it from a subdirectory to a subdomain. The result? A 47% decrease in organic traffic.
It seems that Google’s assurances should be taken with a grain of salt on this occasion.
Why Are Subdirectories Better For SEO?
Despite Google’s assurances that both subdomains and subdirectories are treated the same if you look at the way Google has been favoring subdirectories in its search rankings over the past 3 years it certainly appears as though having a single directory with all your content is going to give you the best results when it comes to ranking your site.
There are a few possible reasons as to why:
Google favors subdirectories because they allow for keywords to be indexed more easily. Since subdomains are distinct from their root domains, keywords contained within both rank separately from one another. This means that a subdomain is unable to help a root domain rank for a specific keyword search and visa versa.
The ranking power of subdomains is also affected by backlink dilution. This phenomenon refers to the fact that a backlink that points back to a subdomain will not affect the root domain in any way.
Say you run a website – example.com – and decide you want to host a blog at blog.example.com to drive traffic to your site. The SEO issue lies in the fact that any backlinks that your fantastic blog content manages to attract will do nothing for the index ranking of your main sight in the eyes of Google’s algorithm.
Google has said that it prefers sites with strong internal linking to those, which use multiple domains or subdomains in the past. The clear winner in terms of SEO is using a single domain or subdirectory as opposed to using multiple domains and therefore having to spread out your content across different locations (such as separate domains for blogs, services, and landing pages).
Where Does That Leave Us?
The subdomain versus subdirectory debate has been raging on for years. Opinions are strong, with proponents for each side arguing that their choice is better. According to Google, both choices are equal in terms of SEO. However, as we’ve seen today that doesn’t seem to be the case. Sure, one-day search engines will have the power to connect subdomains back to their roots. For now, they don’t.
Subdirectories allow search engines to crawl through all your content and attribute it to one source. This is a massive benefit to SEO and makes subdirectories a strong choice for small to medium-sized websites and businesses.