Subdomain SEO: How does it impact website performance?

In SEO terminology, the concept of cannibalization is that if more than one page is optimized for a certain search phrase it confuses search engines. They can't choose to display multiple URLs from the same page on the results page. This is characterized as cannibalization since the site is considered to 'eat' itself for the same search phrase, i.e. to compete with its pages.

Whether it is a product article, comparable product pages for a single item, or similar URL, all are viewed as duplicates and constitute a Google, Bing, Yahoo, etc. indexing issue. In this article, we discuss the cannibalization of sub-domains and the significant consequences of an existing sub-domain approach on your SEO performance. Let us examine why subdomains are used and the potential SEO problems they generate.

What is a subdomain?

First and foremost, there is a lot of misunderstanding about the difference between main domains and subdomains. Some individuals will confuse the two but be assured that they are not the same. The name of your website is essentially your main domain, often called a major domain or a root domain. Now, before you start a semantics debate, keep in mind that the definition comes straight from Google. I'm not sure how you can disagree with it. The main domain name for Inbound Mantra is I didn't say or, which are our site URLs technically.

A subdomain is a part of your website that you want to stand out by having its own identity and content. If Inbound Mantra were to build a subdomain for our blog page (which we don't), the name of the subdomain would be A subdomain allows you to divide sections of your site that are large enough to merit their hierarchy without having to build up a new site with a new domain or confuse visitors with a whole distinct root domain.

Many sites, including Google, employ subdomains in this way. You'll be sent to this website if you need help with any of Google's apps: It's worth noting that the URL is, not

To differentiate a subdomain from a subfolder, that ordering is crucial. In the site structure, unlike a subdomain, a subfolder branches off from the top-level domain. Best practices for site hierarchy emphasize the significance of simplicity, advising companies to keep the number of categories and subcategories in any navigation sitemap to a minimum. According to Kissmetrics, the number of site categories should be limited to between 2 and 7.

However, how does it connect to the domain?

Domain names, as we know them today, did not exist a long time ago, during the days of the ARPANET. Instead, all network directories were labeled with code numbers – IP addresses. 

In the 1970s, you'd have had to use that to go to Instagram – – or Facebook – However, Paul Mockapetris created the DNS idea – Domain Name System – in 1983, which we all still use today. The basic principle behind DNS is its tree-like hierarchical structure, which extends from the main domain to the subdomains.

‍The primary domain is referred to as the Top-Level Domain (TLD). The Second-Level Domain would be the name of your one-of-a-kind website (SLD). A subdomain, in turn, is a third-level domain.

Why use a subdomain?

A subdomain SEO strategy is a clear means of defining a content category or assigning departments their area on the primary site. Many businesses used a website strategy based on subdomains a few years ago for a variety of reasons, including increasing their chances of getting found in search engine results. They might split P&Ls among divisions, with distinct development teams, content writers, designers, and so on. As previously stated, a subdomain structure allows visitors to be directed to certain areas of the site. This is OK and can function in the same way as a subfolder. Just like with a subdirectory method, you must ensure that the many departments involved do not duplicate content or theme.

Subdomains are great if your company has a large amount of information that would be difficult to maintain on a single website. This structure may also be useful if you run multiple major recurrent campaigns that require different landing pages, or if you plan to collaborate with another company and want to split the branding on the project.

Subdomains are useful if you need to segregate information on your website for a specific business reason. A site should use a subdomain in a variety of situations. The most frequent are listed below.

Distinct Regions

A subdomain is an excellent option if you service various regions, whether domestically or globally. If you had a German and an English website, It would be illogical to include those as subdirectories. Craigslist, for example, employs subdomains to service multiple areas. and are two of its subdomains


It doesn't always make sense to put your customer service on your main site. Google, for example, uses rather than The major explanation is most likely due to the site's structure. is a search engine, and Google's Support division is separate from its Search division. As a result, it needs its subdomain to effectively interact with and serve its consumers.


If your firm organizes events, it would be a good idea to separate that area of your website into a subdomain. Again, this is useful when you want to differentiate a portion of your website from your main product or service. Microsoft accomplishes this through its website.


Many businesses prefer to have their blog as a subdomain. In reality, HubSpot does just that. You'll see that the page you're now on is a page. This post, on the other hand, is in the Marketing subfolder of the subdomain. Sites may opt to have their blog as a subdomain if they have a significant enough content campaign in mind that warrants its hierarchy and growth route (more on that in a minute). A subdomain is also beneficial for a blog if you want to establish yourself as a specialized authority.


Companies that sell products can place their e-commerce store on a subdomain in addition to their core product or service. HubSpot also does this. HubSpot merchandise is available at, in addition to our primary software hubs.

Subdomain vs Subdirectory

A subdomain divides your website into sections so that you may create separate content kinds from your base domain. A subdirectory, on the other hand, is a route within your site. A subdirectory is a level in the domain's structure. Subdirectories branch out from the subdomain to which they belong.

Subdomain: impact on SEO

“So, it's a useful organizing tool,” you may be thinking, “but what does a subdomain have to do with SEO and organic rankings?” 

That is an excellent question. 

To begin with, there is no such thing as an organization for the sake of organization when it comes to site structure and hierarchy. A website that is difficult to browse owing to a poor structure will ultimately be penalized by search engines. A poor site layout may cause visitors to spend less time on your page or more time on the page if it takes them a long time to discover what they're searching for, resulting in a less-than-satisfactory experience and perhaps harming your search performance.

By employing subdomains to simplify your site structure, you may help people locate the content they need more quickly, increasing the SEO performance of your website. If you follow the SEO-focused blogosphere, you're probably wondering to yourself, "Wait, I thought subdomains were terrible for SEO?" There has been a lot of discussion about how subdomains may have a detrimental influence on SEO performance, especially that search engines penalize them or have difficulties distinguishing between main domains and subdomains. According to the logic, Google's engines will detect your subdomains as distinct sites from your main domain and rank them accordingly.

They'll be trapped on small SEO islands, and your website won't benefit from any good influence your subdomain might normally give if it were a subfolder. Although the argument over the SEO advantages – or lack thereof – of subdomains continues, there is reason to assume that past predictions of “organic search cannibalization” may have been exaggerated.

What does Google say?

According to Google, subdomains and subdirectories are crawled, indexed, and ranked in the same way. Subdomains, according to Google Webmasters Trends Analyst John Mueller in the video below, do not typically harm a site's results. In reality, he claims that Google is intelligent enough to recognize your main domain and subdomain as belonging to the same website.

Subdomain or subfolder, which is better for SEO?

Google Webmaster Trends Analyst John Mueller addressed the topic head-on in an August 2016 Hangout event, claiming that subdomains typically do not harm site rankings:

“[W]e recognize that some sites use subdomains as different parts of the site,” he said. “And, in the same way, that other sites might use subdirectories.”

Mueller claims that Google's algorithms are quite competent at exploring subdomains and subdirectories and making sense of it all. Having said that, he did warn against the usage of wildcard subdomains, which are intended to send anyone attempting to visit non-existent subdomains to a specified folder. Google's algorithms have always struggled to scan such types of subdomains.

Should you use subdomains in your SEO strategy?

Some SEO professionals feel that Google's crawlers may mistake a subdomain for a whole different website from the main domain. Others, on the other hand, claim that its crawlers can detect subdomains as extensions of parent domains.

Some SEO experts claim that subdomains do not share the authority gained from inbound links (or backlinks) with the original domain. Subdomains, because they are regarded as independent entities from your parent domain, may not inherit any of the link authority you've previously generated to your core website content. Furthermore, if you optimize pages for the same keywords on your main site and subdomain, you may be competing with yourself. Other SEO experts, on the other hand, say that subdomains make your site easier to traverse.

Finally, this leads to a better user experience, which may result in higher engagement rates and, as a result, improved SEO. Subdomains can be useful if you have a huge organization and each subdomain serves a different purpose and functions as a separate business. Disney, for example, includes subdomains like,, and Because these subdomains serve completely distinct objectives, it makes little difference if the sites don't share the same authority from backlinks because they aren't likely targeting the same keywords.

Another advantage, according to several SEO professionals, is that subdomains can aid in the development of specialty authority. For example, you may want your blog to be treated as a different company from your product or service. In contrast, if your site's navigation does not include any significant verticals, you may not need to utilize a subdomain since you want as many connections back to your main site as possible. Subdirectories function just as well as subdomains if you don't have a strong reason to utilize them.

When sub-domains mess up SEO

As a result, the argument continues. When it comes to subdomains and their influence on SEO, there is no one-cut answer, as there is with many other areas of SEO. While Google's official position is that both subdomains and subdirectories can rank equally, a large portion of the SEO community, including key players like Moz, argue that subdirectories are the better choice for your SEO performance and that subdomains should only be used in exceptional circumstances. But, in one situation, you are better-off staying away from SEO. Here is the story.

Let me tell you the tale of 3 websites. 3 Websites were merged into one. And all fell down from SERP.

3 hefty websites,

All SERP top,

Combined one day on sub-domains,

And on SERP went drop, drop, drop.

Lets call the 3 websites,, and

Clubbing the 3 Websites was to be the mother brand. and were the child brands and they were to become part of the mother as sub-domains.

The final proposed configuration was implemented as under:

  • stayed same
  • became
  • became

SEO took a major hit

For a certain keyword (called ranking keyword) was ranking in top 10 and was ranking in top 20.

When the migration happened, the URLs changed as under.

  • became
  • became

Please pay attention to the above paragraph to register what was exactly done.

Any guesses what happened to the SERP rankings?

Since sub-domain is same as a separate website, we expected the SERP rankings to remain almost the same with a short-term dip. But, what happened, taught us a wonderful lesson in SEO. dropped to Page 2, giving us some chance to salvage the ranking.

But, disappeared from SERP altogether. It wasn't even found in Top 200. It just disappeared from Google SERP. It vanished for good. All the attempts to regain the ranking also did not work out. Eventually, we also gave up on all our efforts after reading the sub-domain cannibalization Google update. The SEOroundtable team had done an explanatory post on it. The entire tweet thread from Google SearchLiason makes for very interesting reading.

The only consolation - atleast we were able to figure out the problem.

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