SEO’s Subdomain VS Subdirectory Debate: Here’s What I Learnt

Like the great debate that is iPhone versus Android, SEO marketers have long battled this conundrum: Which is better for SEO – using subdirectories or subdomains?

When I first came across these two terms, believe me, I was as confused as you. But with a little bit of research, the verdict became clear. Both subdirectories and subdomains are ways to categorise and organise various webpages in a website, but they have different implications on SEO and user experience. Essentially: same, same, but different.

Without wasting more time, let’s take a look at what they are and what each of them are best used for.

What is a subdomain?

A subdomain is regarded as a different website than the main one it branches off from. While there remains an association of the subdomain with the main domain, the subdomain is treated as a standalone site.

Here’s how you can differentiate the two based on URL:

• Main domain: example.com
• Subdomain: sg.example.com

Further evidence that subdomains are separate websites lies in how Google treats them. Subdomain websites need to be verified separately in Google Search Console. Also, SEO ranking factors like backlinks in a subdomain do not affect the ranking of the main domain. 

What is a subdirectory?

Subdirectories are part of one main domain, and are used to categorise different sections of the website. Similar to desktop folders, they work hierarchically to organise webpages within a website. Hence, some people also call them subfolders.

Here’s what they look like according to their URLs:

• Domain name: example.com
• Subdomain name: example.com/sg

When should I use a subdomain?

Due to their property of being a standalone website, subdomains are ideal for a variety of purposes. Here are some scenarios in which I’ve found subdomains generally work better than subdirectories:

For a staging website
Subdomains work great as staging websites, for example, in cases where you might be testing out a new website layout. This is better as your subdomain site can have subfolders that mirror that of your main domain. If subdirectories were used instead, they may interfere and complicate the website architecture with existing, live sections of the website.

You can prevent accidental discovery of your staging site by ensuring there are no links from your main domain to the subdomain. By setting a password, you would also enhance privacy and block spiderbots from crawling your staging website.

For branding
What do you do if you have certain specialised content that is distinct from the rest of your website, but you still want to retain the brand association with your main site? That’s where a subdomain site comes in handy. This is commonly seen in news websites: Specific categories like cooking recipes or health articles may get their own subdomain because these are evergreen content which are rather distinct from the fast-changing updates of the main news sections.

For SEO
Depending on your content and SEO goals, a subdomain rather than a subdirectory may be the better choice. This is advisable only if you do not want ranking factors from the main domain to affect the ranking of your subdomain, and vice versa. Usually, this is recommended if your content (and targeted keywords) for the subdomain and main domain do not overlap.

When should I use a subdirectory?

For the cases mentioned above, they would seem to be more of exceptions than the norm. In most cases, using a subdirectory is the default choice for organising webpages and website content. Hear it from Google themselves: Google Webmaster Trends Analyst, John Mueller, recommends only using a subdomain when it has something different to offer compared to the rest of the site.

Yet, there are some clear reasons for using subdirectories – besides it being the default choice. You’ll want to consider using subdirectories if these goals rank high on your priority list:

For authoritativeness
Comprehensive, accurate, and relevant content can increase your website’s authoritativeness (recall: E-A-T for SEO). By including webpages as subdirectories rather than on a separate site, you are building a more comprehensive, content-rich website, which may help boost your site’s ranking as well.

For user-friendliness
If you look at your content and think that there may be instances where users will want to browse through the different sections quickly and conveniently, putting them in subdirectories will be easier than in subdomains. For example, you may have users who want to buy cooking ware and kid’s apparel at the same time. Instead of separating out your cooking ware products into a subdomain, leave them as subdirectories to make it easier for users to navigate without leaving your main website.

For SEO
If your content is relevant and valuable, and has the potential to attract traffic to your site, putting it in subdirectories under the main domain can boost the overall ranking and traffic to your site, rather than splitting up the traffic to a subdomain. This is especially true for blog pages. In fact, many brands which formerly had their blog pages in a subdomain experienced a surge in traffic and ranking once the blogs were relocated into a subfolder on the main website.

Conclusion

It doesn’t take a hawk-eyed reader to realise that I’ve included ‘For SEO’ for both the subdomain and subdirectory sections. That’s because it really depends on the content in question as well as your SEO goals.

Similar content? Go for subdirectories, as this could help raise the ranking of your website. Distinct content? Go for subdomains, especially if you don’t want your content to cross-affect SEO on both sites. All that said, sometimes, limitations on the end of website developers or hosting platforms may leave you with no choice.

When that happens, it’s a small comfort to know that Google doesn’t treat subdomains or subdirectories any differently. Subdomains may be regarded separately, but it doesn’t have any added advantage or disadvantage in the eyes of the search engine.

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