Subdirectories are also known as subfolders, so these two terms are interchangeable. They will have the same meaning throughout this post, so please don’t get confused.
Okay, so what are subdomains and subdirectories?
Have you ever noticed something like https://blog.abc.com in the address bar of your browser when you have visited a website or web page? I’m sure you must have seen that if you have been using the web for some time now. https://blog.abc.com is the entire website URL where abc.com is the main domain name, while blog.abc.com is the subdomain part of the URL. The website abc.com can have multiple subdomains like that and it’s possible to have one subdomain for every single page.
Even though a subdomain is a part of the main domain, search engines treat them as separate websites altogether.
Subdirectories or subfolders, on the other hand, are parts of the same website. You must have seen or noticed something like https://abc.com/about. This is a complete URL of the website abc.com where abc.com is the main domain or main folder and abc.com/about is a subfolder or subdirectory. It basically represents the About page of the website. If you are on the blog page of the website, the URL in the address bar would be like https://abc.com/blog.
Search engines treat subdirectories as part of the main website, not individual websites. And that is the main difference between a subdomain and a subdirectory.
So, what we can simply understand that subdomains and subdirectories are basically two different ways of representing the inner pages of a website. A subdomain can be treated as a standalone website, which means that a subdomain can also contain a subdirectory. For example, blog.abc.com is a subdomain and it can also contain a subdirectory like blog.abc.com/support.
So, I hope subdomains and subdirectories are clear now. Let’s discover the exact pros and cons of each of them from the SEO point of view.
Subdomains
Like I have mentioned already a subdomain is like a separate website for search engines, primarily Google. Google Search Console clearly suggests that subdomains have to be verified separately from the main domain’s content.
In a webmaster video, Google’s John Mueller recommends site owners or webmasters that they have to verify subdomains in the Search Console separately from the main domain, make changes to settings and track performance of each subdomain.
So, it is clear that a subdomain is a separate standalone site for Google.
Practical reasons to use a subdomain
Subdomains are used basically for a couple of practical purposes such as Technical, Branding and SEO
Technical purposes: When the web developer is asked to redesign an existing website for a better look and performance, the developer cannot do changes to the existing main site because it’s live already. (I mean he or she can but that’s not a good practice.) This is where a subdomain comes into play. Since a subdomain is a different site that the search engine cannot crawl until and unless you submit the site for search engine indexing it is not going to affect the main domain or the main site by any means. The developer can install a new theme, design new templates or try new plugins or other items on the subdomain and design it as a staging site in whatever way he or she can. The main site is completely safe. But the developer has to make the staging site password protected on the subdomain.
Branding purposes: Some businesses choose to brand just one particular section of their main site, while keeping it away from the rest of the main site. In that case, a subdomain is a great option. Usually, you can see the support pages of most business sites branded as subdomains like abc.com.
SEO purposes: Imagine if you run a shoe business and have an e-store that sells shoes for men and women. After a certain period of time you realize that people have a lot of questions about some particular pairs of sports shoes of your brand and they want to know the exact benefits of the shoes. You also realize that they are looking for further help with fitness tips from you as you are also a fitness coach. In that case, you would want to launch a separate site or blog to provide tips and tricks to your customers. You may host another website separately, but you actually don’t have to host a new site or blog because a subdomain can get the job done. Fitness tips ideas are different than your shoes business, but if you host a subdomain for the fitness tips, it can get ranked without affecting your main shoes site or getting affected by that. So, this is the SEO benefit of using a subdomain. Both are independent sites and both can rank individually.
Subdirectories
Subdirectories are used to give the website visitors an understanding that the website is actually an authoritative source for them that gives complete knowledge about a particular topic.
Subdirectories can also help in establishing connection between different sections as sections overlap. If you are a potential buyer of wedding clothes, you might also be interested in buying some matching jewelry items. And if you could get them all at one place, you would happily purchase them. So, the point is a site that offers all the related items is more preferred than a site that only offers one single item.
So, a subdomain or a subdirectory? Which is better for the main website, for the business and for the branding?
This is debatable. There is no clear answer to this. Both are relevant in terms of giving the main site more expansion, more authority and adding more value to the resources or content of the original site.
So, it is the choice of the website owner to go for a separate subdomain or a subdirectory structure. If the site owner thinks it’s better to have a separate standalone site, then a subdomain is better. And if he or she finds that a subdirectory can be more beneficial for their business and their audience, then a subdirectory structure of their main site is the way to go.
If a particular section works best for the business, for branding and for its potential target customers or audience when it’s used as a standalone website, follow the subdomain structure. You have to be sure that the section is not similar to all the other sections. But if the section works better along with other sections, you cannot isolate it, and hence you should follow the subdirectory or subfolder approach.
You just cannot have a clear answer as to what is right or what is wrong, which of the two ways is better. The website owner or the webmaster has to take the business, branding, and SEO purposes into consideration before making the important decision.