Subdomains are often added to improve specialization or to differentiate the site from the main site, but some people may be concerned that this will have a negative impact on SEO, as search engines will recognize the subdomain as a completely different site.
In this article, we will introduce the reasons why there are negative effects and provide an easy-to-understand explanation for such people. We will also introduce things to be careful of when operating the site, and whether to choose a subdomain or a subdirectory depending on the situation, and derive the optimal solution.
First of all, what is a subdomain?
A subdomain is a domain that precedes a main domain. For example, if we take “Google,” “https://www.google.com/” is the main domain (root domain), but in the case of Gmail, the URL would be “https://mail.google.com/.”What is a subdirectory?
In contrast, a subdirectory is a term that refers to a part that is added later rather than within the main domain. For example, the URL for a Google image search is “https://www.google.co.jp/imghp”, where “/imghp” corresponds to the subdirectory. This format is mostly used to further divide pre-prepared pages. For example, a sports-themed site can be managed and operated by dividing it into “/soccer” and “/baseball”. Unlike subdomains, which are suitable for creating completely new content, subdirectories are used like folders to divide a page.What is a subdirectory?
In contrast, a subdirectory is a term that refers to a part that is added later rather than within the main domain. For example, the URL for a Google image search is “https://www.google.co.jp/imghp”, where “/imghp” corresponds to the subdirectory. This format is mostly used to further divide pre-prepared pages. For example, a sports-themed site can be managed and operated by dividing it into “/soccer” and “/baseball”. Unlike subdomains, which are suitable for creating completely new content, subdirectories are used like folders to divide a page.Conclusion: Subdomains don’t have a negative impact on SEO
To conclude this topic, there is no need to worry about subdomains having a negative impact on SEO. The reason is that Google itself denies the existence of any negative impact from domains. This means that there is no longer any need to choose a domain based on SEO.Why subdomains don’t hurt your SEO
Subdomains do not belong to the main domain, but are treated as “separate sites.” This is the crucial difference from subdirectories, but subdomains can still inherit some of the reputation that the main domain has. Since you can inherit the power of an already developed site, there is no need to develop domain power from scratch. The SEO measures you have taken so far will not be wasted, but rather will have a positive effect. The costs you have spent on measures will not be wasted, so you can lead your website to a new stage with peace of mind.[Caution] However, we recommend using subdirectories while your domain authority is still weak.
One thing to keep in mind is that subdomains are dependent on the power of the main domain. In other words, even if you develop a subdomain with weak domain power, the power will not be fully conveyed and you will not be able to effectively implement SEO measures. If you prepare a subdomain when the power is insufficient, you will have to strengthen the site in parallel with the main domain. Because the power is dispersed, it will take more time to implement SEO measures and the cost of doing so will tend to be higher. It is recommended that you choose to strengthen your domain directly while its power is still weak. In other words, when your domain power is weak, you should prioritize the development of subdirectories over subdomains. The shortcut to success is to wait for your main domain to grow before proceeding with the creation of subdomains.The advantages of subdomains and subdirectories
Both subdomains and subdirectories have their advantages and disadvantages. Let’s examine which one is more beneficial for each situation. The first step towards efficiency is to reconsider the usage.The important thing is the difference in purpose (direction)
Before judging the pros and cons, you should first consider the “difference in usage.” Subdomains are used when you want to handle different themes within the same brand. On the other hand, subdirectories are used when you want to divide the same brand and theme into more detailed genres. For example, Yahoo! Shopping, Sports, Yahoo! Auctions, and Travel are all under the same brand, but the themes they cover are completely different. Therefore, they have separate domains, with shopping at “https://shopping.yahoo.co.jp/” and travel at “https://travel.yahoo.co.jp/,” making it clear that they are separated. However, the situation is different for the soccer page “https://soccer.yahoo.co.jp/” on Yahoo!. “https://soccer.yahoo.co.jp/japan/” is used for the category dealing with the Japanese national team, but “https://soccer.yahoo.co.jp/jleague/” is used for J-League, and “https://soccer.yahoo.co.jp/ws/” is used for overseas soccer, each with its own subdirectory. With these prerequisites in mind, let’s consider which choice is smarter and will have a better impact on your SEO.When to choose a subdomain
The advantage of a subdomain is that it keeps costs down. Acquiring a completely new domain requires money, but if you choose a subdomain, you can keep the main domain as the parent. This not only reduces acquisition and management costs, but also gives you an advantage in terms of branding. Another feature is that you can create more specialized pages while still inheriting the characteristics of the main domain, so if you choose a subdomain when creating a page for a new business you are focusing on, you will be able to see the benefits. By changing the page itself, you can perform access analysis independently, making it easier to operate when making improvements, and making it easier to provide the services users need. On the other hand, one disadvantage to be aware of is that, because it requires the creation of highly specialized pages, it will require effort to provide depth to the content and to differentiate it from the main site. As a result, it cannot be denied that it may take time and money to increase the volume of articles.When to choose a subdirectory
The advantage of subdirectories is that they allow you to increase the number of more independent and specialized pages within the same genre. Since it is an effort to increase content in a concentrated manner, it is attractive because it is easier to attract support from those who are looking for core information. Access analysis can also be performed by tracing from the main domain, which is convenient and allows for extremely simple operation. As mentioned above, this is also a method that can easily lead to strengthening the main domain, so it is particularly effective when you are in a situation just after launch or when you want to set up a page that staff can easily manage. The disadvantage is that there is a risk of posting duplicate content multiple times. As a result, you need to consider the possibility of a decrease in access and penalties, and you will need to put in place a management system to prevent problems from occurring. Also, if you start a service that is completely different from what you have done up until now, and you deploy it in a subdirectory, Google may not know what genre the site is in. This will cause the genre to become blurred, and the authority in the genre that you had gained with the main domain will decrease, and the ranking of your existing pages may drop.Don’t forget to set up cross-domain Google Analytics
If you select a subdomain, it will be considered a site unrelated to the main domain, so if you are using GA (Google Analytics) measurement, cross-domain settings are required. If you do not do this, when a visiting user continues to access across domains, the session will be interrupted, causing problems. To set up cross-domain, you need to change the tag in Google Analytics and execute “referral exclusion settings”, “filter creation”, and “goal setting” in that order. This setting is called cross-domain tracking, and you should not forget to set it up in advance. It may seem like a very complicated and difficult task, but if you follow the steps it won’t take much time. For detailed information on how to set up cross-domain, please refer to the following article.