The URL difference between subdomain and subdirectory 

newsitefolder.primarydomain (Subdomain – see position of “newsitefolder”. Comes before the primary domain) 

vs.

primarydomain/newsitefolder (Subdirectory – see position of “newsitefolder”. Comes after the primary domain)

  1. Is there a real difference between subdomains and subdirectories? 
  2. Will performance suffer just because one chooses a subdomain over a subdirectory?
  3. Is there ever a point of choosing a subdomain over a subdirectory?

These are the three main questions that really matter. If you are looking to learn enough SEO to answer all three, you’ve landed on the right article.

Let’s start with a quick word from Google itself:

“Search Engines are fine with subdomains and subdirectories. They index and rank both in a similar way. Subdomains, when used properly, can be a great asset to obtain SEO rankings. Google’s crawlers can identify subdomains as an extension of the parent domain.”

Ok. So one thing is clear, whether you implement a subdirectory or subdomain, Google will still visit your pages. Google will crawl your pages. Google will index your pages. And quite likely, google will rank your pages (for better or worse).

No clear distinction yet. So maybe it's better to take a step back. Let’s describe the basic definitions.. 



What is a Subdirectory?

A subdirectory is the part of the url that houses a specific subset of content. A website is like a filing cabinet, the folders within the cabinet would be the subdirectories of your site. Individual directories are located to the right of the domain. 

Eg: primarydomain/newsitefolder



What is a Subdomain?

A subdomain is a division or alias of your domain that can be used to organize your existing website into a separate site. Typically, subdomains are used if there is content that is distinct from the rest of the site. Subdomains are indicated by the section to the left of the root URL.

Eg: newsitefolder.primarydomain



A Deeper Dive

Essentially, this whole debate comes down to site architecture. Plus, the likelihood of search engine bots finding your pages.

As we’ve mentioned, you need search engine bots, crawlers and spiders to find your pages because if they don’t, well, you don't get indexed, rendered or ranked. And then it’s “bye, bye new human web visitors.”

With that being said, imagine your website as one big library of pages. We’ll refer to this big and stunning library as the domain

Instead of keeping books, your special domain is the library that houses all your super special pages (web pages).  These pages are so special, your library is visited by hundreds of people everyday. 

Now assume you are the librarian, tasked with maintaining the welfare of the domain. You protect the integrity of the library and manage its performance (ensuring many people come to visit your library everyday).

Assignment number one, as librarian: decide how to add a new room to the library. 

For the sake of your website, imagine each room in your library represents a new folder for your website. Each room offers an opportunity to group related pages in one place, making it easier for visitors to find more of the same kind of pages they like. 

To expand your library (to add a room), you are given two options:

  1. Build a room inside the primary domain (the main library) - the subdirectory approach
  2. Build a separate house just outside your main domain - the subdomain approach



Subdirectory Deep Dive:

Subdirectories are a pathway within your site. They are a branch off from the primary domain.

Per URL structure, subdirectories appear after the primary domain name in the URL. 

For example: primarydomain/newsitefolder 

REMEMBER: If you are thinking about site architecture. When you think subdirectory, think extension. 

 In the back end, you create a new web folder that is inside your primary domain folder. 

When to use subdirectories: Typically, if all of your content falls under the same general topic, best to stick to subdirectories. This is to say, if you have sections of a site that are really extensions of a broader topic, then don’t bother creating a subdomain.



Advantages of subdirectories

    1. From the perspective of search engines, the overall backlink profile of the primary domain is more likely to be credited towards subdirectory pages. External links that point to folders/pages off the primary domain are more likely to boost the authority of other pages linked through a subdirectory. This is not the case when it comes to subdomains.
    2. When it comes to tracking site performance, in platforms such as Google Search Console/Analytics,  you don’t need to view results separately. The data is consolidated for the entire site, rather than having to look at two data points as a result of using two domains.

In your library you may choose to house many rooms. Each room is a web folder of different pages. 

These subdirectory folders are simply extensions of the same library. Why? Because they extend what you can offer WITHIN the main library by adding another room INSIDE the main building.  

Your library may have a room to store your categories. Or you can add a room to store all your blog pages. 

With the same rationale, you may choose to house all your product pages in a store that’s within your primary domain. 

This way when users enter your library, browsing other content, they don’t have to leave the main domain before finding your new store.

If you think about it, you are quite likely to attract more customers to your store, if it can be found in the same place as all the other popular rooms. Similarly, you are more likely to be discovered online if your page is contained in the subdirectory of an authoritative site. 

If your choose to build this new room of products inside the primary domain, your subdirectory URL would look like this:

primarydomain/Product

Or primarydomain/Store



Subdomain Deep Dive

Per URL structure, subdomains appear before the domain name in the URL. 

For example: newsitefolder.primarydomain 

REMEMBER: If you are thinking about site architecture. When you think subdomain, think separation. 

In the back end, you create a new web folder that is outside your primary domain folder. 

When to use subdomains: Subdomains segment your website so you can establish an entirely separate approach to web management on the same primary domain.



Advantages of subdomians

  1. From the perspective of Search Engines, a subdomain is seen as a unique website unrelated to the main domain. In a way you are able to establish a separate identity for your site.
  2. Subdomains can be used to target a specific market segment or demographic.

Let's examine how the subdomain approach would affect the expansion of your library - by mode of separation. 

In your library you can house many rooms. OR you can build an entirely separate building just outside the main library. This is essentially the idea behind a subdomain. 

Webmasters apply subdomains when they’d like to create a new experience on a site, one that cannot be directly linked with the main proposition of the primary domain. 

If you think about it, you are quite likely to attract less customers to your store, if it's not in the same place as all your best pages. With product pages housed in  a store that’s just behind your main library, some visitors might miss the newly created destination entirely. 

If your choose to build this new room of products outside the primary domain, your subdomain URL would look like this:

Product.primarydomain

Or Store.primarydomain



A quick thought experiment

If you are thinking subdirectory, you are thinking extension. Build a new room, within the primary domain.

If you are thinking subdomain, you are thinking separation. Build the new chamber outside the main domain but within the premises of the URL.

What’s the consequence of each?

Let’s bring it all together: 

  • To get ranked online, we’ve noted that search engine spiders have to discover and visit your site. 
  • These bots crawl your site, browse the pages in your library. 
  • Then they index the pages they find in your library, store a record so online users know where to find your content. 
  • Then search engines rank your pages, decide how popular your pages should be. 
  • The goal is to rank on the first page of a search result. This is what attracts the maximum number of human visitors to our library. 

Never forget, as a librarian you are expected to grow the success of the library. 

You now understand the fundamentals of what it takes to rank online (we’ve stated this twice now). You know how important it is to be discovered by search engines before you can be discovered by new users. 

You know what it will mean for your primary domain, or library, if you choose to extend your number of pages by adding a subdirectory inside your primary domain. 

You also know what it will mean for your primary domain, or library, if you choose to expand your number of pages by adding a separate subdomain outside your primary domain. 



Review these quick facts

  1. Page authority is important for a page to rank online. Search engines use the number and quality of external links to determine the authority of a site.
  2. Page authority doesn’t easily transfer from primary domain to subdomain. Page authority more easily transfers from primary domain to subdirectory.
  3. Search engines are likely to consider a subdomain as separate to the primary domain



Let’s make it easy for you

Remember, there is no wrong answer to the thought experiment above. 

You are free to manage your site in any way you choose. 

But as an industry standard, making the choice between Subdomain vs. Subdirectory is rather straightforward. And the more you know about SEO, the likelier you are to choose subdirectories.



Best Practice

If your domain is all about one broad topic, and general one approach. All your URLs should follow the subdirectory format:

primarydomain/Blog 

primarydomain/About

primarydomain/Product 

If you are expanding your site but looking to build a new section that may be viewed as unrelated, consider:

ProductX.primarydomain

ProductY.primarydomain

ProductZ.primarydomain



TRAM SEO Conclusion

As a summary, let’s answer the first three questions we began with: 

  1. Seems like a cosmetic choice really. Is there a real difference between subdomains and subdirectories? 

Yes. Yes. There is a difference. Read above and below. 

  1. Will performance suffer just because one chooses a subdomain over a subdirectory? If not, what’s the fuss?

The more authority or equity a page is deemed to have, the better the ranking, the more user visits. 

Setting up a subdomain will split the way search engines review and rank your site. Although the primary domain and subdomain are quite clearly connected, the authority of one will differ from the other. That which is likely to rank better is the section that has attracted the highest number of quality links. 

A subdirectory won't automatically receive the same page authority as the folder or page with best link equity (within a primary domain). However, compared to a subdomain,  there is a much better chance of a subdirectory taking advantage of the primary domian’s link equity. 

 

  1. Is there ever a point of choosing a subdomain over a subdirectory?

Yes, there are instances when a subdomain makes more sense than a subdirectory. Basically, if you don't mind cutting off link equity from the primary domain to the subdomain + if you need to create a new section of a site which may not be directly related to the core of your standard offering. 

Car companies that aim to de-prioritise their used vehicle will create a subdomain, separate new from old products. 

Non eCommerce brands that want to sell products may test out the proposition on a subdomain. 

Some webmasters opt to rely on subdomains when serving web users of different languages. 



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