Subdomain vs Subdirectory: What Strategy is Best in 2021? – In this article I am giving some practical advice on the subdomain vs subdirectory debate and choosing the right structure and hierarchy for your website.

Subdomain vs Subdirectory: General Questions

Before we get to the nitty-gritty of the topic, it’s worth clarifying some of the terminology used in writing on subdomain vs subdirectory.

What is a Domain (Name)?

Generic Definition of Domain (Name)

A domain (name) is the web equivalent of a physical address in the real world. A domain is used as a memorable name for a resource on the web, generally a website.

A domain name points to an IP address and has a minimum of two components: a Second Level Domain (SLD), which is the actual name of your website; and a Top Level Domain (TLD), which is the suffix attached to the SLD.

Technical Definition of Domain (Name)

A domain name is an identification string that defines a realm of administrative autonomy, authority or control within the Internet (source: Wikipedia):

In general, a domain name identifies a network domain, or it represents an Internet Protocol (IP) resource, such as a personal computer used to access the Internet, a server computer hosting a website, or the web site itself or any other service communicated via the Internet.

Types of Domains

The following are the types of domains commonly accepted:

• Top Level Domains (TLDs) are the domains at the top level of the internet domain system. ‘There are over a thousand TLDs available but the most common include .com, .org, .net, and .edu‘ (source: hostinger.com)
• Country Code Top Level Domains (ccTLDs) are domains based on international country codes. They are generally used for country-specific websites such as .ie for Ireland or .pt for Portugal
• Generic Top Level Domains (gTLDs) are top level domains that are not based on a country code
• Second Level Domains (SLD) are domains that are below top level domains. For example, in increasily.com ‘increasily’ is the SLD and .com is the TLD

What is a Subdomain?

A subdomain is the part of a domain that comes right before the main domain name. For example, in office.sherryfitz.ie ‘office’ is the subdomain of ‘sherryfitz.ie’.

What is a Subdirectory?

A subdirectory is a subsection (for example, a folder or category) within the main domain name.

Subdomain vs Subdirectory: SEO Strategy

If you are thinking about your SEO strategy, choosing between subdomain vs subdirectory could play a significant role in the rankings and visibility for your pages.

For this reason, it’s important to choose wisely. Below I am listing a number of elements for you to consider.

What Google Says

The two main mentions by Google about subdomain vs subdirectory have come in the form of videos by respectively Matt Cutts and John Mueller. Let’s see what they say.

Video by Matt Cutts

This is the first video posted by Google on the debate subdomain vs subdirectory.

Quoting from the video:

They [subdomains and subdirectories] are roughly equivalent

Video by John Mueller

This is arguably the most quoted video when it comes to the debate subdomain vs subdirectory. It’s often used to reinforce the argument that Google makes no difference between subdomains and subdirectories.

Quoting from the video:

Google web search is fine with either subdomains or subdirectories

What’s the Difference between Subdomain vs Subdirectory?

Before arguing what’s best for SEO, it’s worth taking a look at the differences between a subdomain vs subdirectory website structure.

Matt Cutts said that the two were roughly equivalent.

John Mueller said Google was fine with both but then he added three differences at the end of the video:

1. Subdomains need to be verified separately in Google Search Console
2. Performance for subdomains needs to be tracked separately
3. Settings for subdomains need to be changed separately

From the focus given to the word separately and per domain, you might have already guessed what I am going to write next: Google treats subdomains as separate entities from the main domain.

What does this mean?

Domain Authority and Subdomains

The fact that Google treats subdomains as separate entities means two things when it comes to domain authority:

• Any link, internal or external, to content on a web page within the subdomain does not contribute to the authority of the main domain
• At the same time the content on the subdomain pages, because it belongs to a separate entity, doesn’t benefit from the authority of the main domain

Links and content are considered by Google as two of its three main ranking factors, the third being RankBrain (source: semrush.com).

What is Domain Authority?

The domain authority for a website is a measure describing how successful (and valuable) a domain is in search results within a given topic area or industry.

What’s Best for SEO?

There is a strong case arguing that switching from subdomains to subdirectories will increase the rankings, visibility and traffic for your website.

SEMrush mentions a few examples in this article about subdomain vs subdirectory:

I shared this on Twitter about 4 weeks ago, just wanted to re-share as it’s still going up… pic.twitter.com/KVKbdmnLfN

— Andy Chadwick (@digitalquokka) October 29, 2020

Not wanting to start an argument or anything, but here’s what happened when a retail client’s blog was moved from a blog. subdomain onto a /blog/ subfolder 📈 pic.twitter.com/LxMWBV2JAu

— Stephen Kenwright (@stekenwright) October 20, 2020

Both cases are relatively recent and show a significant increase in organic traffic following the moving from a subdomain structure to a subdirectory one.

Subdomain vs Subdirectory: Use Cases

We now know that if what we care is rankings, visibility and traffic, moving to subdirectories has its benefits.

Having said that, here are some cases where keeping a subdomain structure makes sense. Let’s take a look.

When to Use Subdomains

You might want to consider keeping your subdomain structure if you are happy with your overall organic traffic and your website falls under one or more of these use cases:

Different Departments

One common use case for subdomains is when you want to separate a specific department from the main domain.

For example, Google uses support.google.com to separate its support service from its main domain (and so does HP with support.hp.com).

The counter-argument for this example is that Google doesn’t really have to make a big effort to rank its pages on…Google.

Different Regions or Languages

If you have a multilingual website or a multi-regional one, it might make sense to keep the corresponding regions or languages as separate from the main domain.

The counter-argument here is that the same result is perfectly achievable through a subdirectory site structure, which brings the additional benefits of higher rankings.

Blog

Some companies want to keep their blog as separate from the main website. Hubspot with blog.hubspot.com is one of the main examples.

Again, Hubspot.com is not a website struggling with domain authority and its content marketing scope is so large that it could make sense to have a separate entity for the blog.

Store

Many websites decide to have the ecommerce part of their business as a subdomain.

For the reason concerning domain authority and visibility, I am not particularly in favour of this choice and I would not recommend it for the average online store (especially brand new ones).

Events

Microsoft with events.microsoft.com decided to separate its events section from the main domain. Again Microsoft doesn’t need to make an effort to rank its pages.

Mobile

Before websites were responsive to screen sizes, it was common practice to create a mobile version of the website and upload it onto a subdomain, generally mob. or mobile.

Some companies like Facebook and Twitter still use this solution for those mobile users who access their website through a mobile web browser (and not through their mobile app).

When to use Subdirectories

The short answer is always use a subdirectory site structure unless your website falls under one of the use cases above.

Even then, make sure you evaluate the pros and cons of your choice:

• If you want to maximise your visibility on Google, go for the subdirectories
• If you generate regular content that would benefit from your main domain authority, go for subdirectories
• If you want your main domain to benefit from the content you regularly write, go for subdirectories

Conclusion

Choosing the right site structure strategy could have a significant impact on your success online.

Currently, I am working on two projects concerning a move from subdomains to subdirectories for respectively a large Irish auctioneer and a large ecommerce website in Italy.

If you need an SEO consultation about this task, make sure you get in touch.

Subdomain vs Subdirectory: Sources

• Domain Name (Wikipedia)
• What is a Domain Name (Hostinger)?
• What is a Domain (Host.ie)?
• Subdomain vs Subdirectory (SEMrush)

Subdomain vs Subdirectory: Images

Featured and in-content images from storyset.com