The debate between SEOs (Search Engine Optimizers) on whether to use a subdomain or a subdirectory for organizing website content has been around since the beginning of Search Engine Optimization. Some of it is left up to the personal preference and past experiences of the SEO, but depending on the situation, it sometimes makes more sense to use one method than the other. In order to gain a better understanding of when to use each organizational tool, we’ll define each and list some instances where it would be better to use one method rather than the other.
A subdomain is usually a section a root website that has a different DNS alias. An example of the root domain of a website could be “example.com”. An example of a subdomain would be “subdomain.example.com”. Subdomains should generally be used when there is enough content to support a standalone website, but when the content is still closely associated with the main subject or theme of the website. When using subdomains, the SEO has to be careful, though. Depending on the algorithm of the targeted search engine(s), they might not rank as high as when the content is segmented into a subdirectory of the site. They are effectively treated as a separate website by search engines, and multiple sites with the same root domain with similar content do not generally rank as high as multiple pages inside the same website. If you include the same content in multiple subdomains, the search engines will quickly catch on and start degrading the search result ranking because they will be considered as multiple sites with the same content.
Organizing content into subdirectories is generally easier to maintain than if the content belongs to different subdomains. The content is inside the folder structure of the root website so it can be easily moved without having to modify the DNS settings of website. This is not true for a subdomain. The DNS records must be changed to preserve the integrity of the link. Subdirectories are the best choice when you want a page to target specific keywords that are related to each other and the root domain’s theme. Subdirectories can rank higher in SERPS (Search Engine Rank Pages) since they are closer to the host domain.
Subdirectories also add content to your website, which can be good for new websites because they give search engines more content to help them judge how pertinent they are to the keywords the user is using for their search. A page that is a wealth of keywords, for example a blog, should be contained in a subdirectory of the main website since it is closely related to the main domain and can be used to increase the ranking of the main site.
Both content organization methods are useful tools in the SEO’s repertoire. Both are equally valid in certain circumstances. The SEO should take the algorithms and practices of the targeted search engine(s) into consideration when deciding whether to use either method of structuring their website content. Depending on their target audience, page ranking strategy, and the organization of the content, one method might be more useful given the current situation. As in most subjects dealing with technology, it all depends on the problem at hand to determine which one is better than the other.