The Pros and Cons of Subdomains

A client recently inquired about the use of subdomains versus subfolders and the benefits of each. From an SEO perspective, much of our research points to using subfolders rather than subdomains as the best answer. However, there are some cases in which a subdomain can be a good choice. The following points illustrate the pros and cons of subdomains.

Subdomain PROS

  • Concise and easy to remember URLS can make marketing and branding easier, but it may also take some client education to ensure that users don’t type in the www.
  • Links between a subdomain and a main domain may be treated with slightly more weight than an internal link, but if the subdomain and main domain are hosted in the same place links between the two will be given the same weight as internal links.
  • It is possible to get links from directories in multiple categories if the topic of the subdomain would fall under a different category than the main domain.

Subdomain CONS

  • It takes more work to build up page rank and links on a subdomain just as if it were a new top level domain.
  • The content on a subdomain is not necessarily considered relevant to the main domain.
  • The relationship to the main domain is not as clearly established as a subfolder to the main domain.
  • Search engines don’t always pass the same authority from the main domain to the subdomain.
  • Link juice is split between main domain and subdomain.
  • Subdomains are often not seen as distinct enough to show up in the search results as a different site alongside the main domain. So, dominating the space on page one with your main domain and subdomains is unlikely.

Many of the subdomain cons are the subfolder or subdirectory pros. The advantages of subfolders are that they directly contribute to the content and authority of the main domain. Subfolders keep the link juice concentrated on the main domain rather than splitting it as a subdomain does. Therefore, it is easier to build up page rank and links to the main domain. Some of the subdomain pros can also be seen as the subfolder cons. For example subfolder URLs are often not as concise and easy to remember as a subdomain. Also, as a general rule it is better not to bury pages too deep within folders making them hard for users and search engine robots to find. In general, subfolders tend to be the better choice unless there is a really compelling reason to use a subdomain. If you have questions about redesigning the architecture of your site, please contact us.


5 Responses

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  2. Dan on 22 Jan 2010

    sorry, i meant link juice, not page rank

  3. Dan on 22 Jan 2010

    good post but i think your point about page rank being split between the subdomain and domain is inaccurate. as you note, subdomains are treated as a new top level domain so if your subdomain is in a different niche i really don’t think you will be splitting the page rank – that would only occur if your subdomain was competing with your domain.

  4. ssawall on 23 Dec 2008

    Thank you for the comment and questions, Tom. In response to your inquiries, subdomains can be a good approach for blogs when adding a blog to an established site. Also, from a marketing perspective, many organizations find that blogs fit in a little better on a subdomain rather than in the structure of an existing site.

  5. tom funk on 05 Dec 2008

    Thanks for the excellent post ssawall. Where we see this question coming up most frequently is in structuring of a blog as an add-on to an established site.

    It seems from a search perspective, there are two potential strategies:

    1) My blog will be so noteworthy that it will attract links better than the rest of my site. It will attract rank and traffic in its own right, and will boost the overall rank of the domain (therefore, go with subdirectory approach, right?), or

    2) My main domain will continue to attract most of the links. The blog will have some rank, but mostly it’s value will be in linking to the main domain (so go with a subdomain for the blog)

    What do you think?

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