Ask an Expert: Subdomains, Subdirectories and SEO Implications

“Ask an Expert” is an occasional feature where we ask ecommerce experts questions from online merchants. For this installment, we address a series of questions on the proper use of subdomains.

For the answers, we turn to Michael Stearns, CEO of the Internet marketing and design company HEROweb, and a contributor to Practical eCommerce.

What is a subdomain?

Michael Stearns

Michael Stearns

“A subdomain is a specific name that you define in your DNS settings for your main domain. A subdomain can be an effective device for extending your brand and deploying additional content and technology related to your main website. Here is an example subdomain:

“In this example: ‘com’ is the top-level domain; ‘joespopshop’ is the second-level domain; ‘members’ is the subdomain. For this discussion we will use the generic term ‘main domain’ to describe the site address of

“The key alternative to a subdomain, when deploying and integrating other web content, is a subdirectory. A subdirectory would simply involve making a directory under your main website directory. An example is:

“Beyond subdomains, you can always set up additional top-level domains and websites to deploy niche content.”

When should a website owner set up a subdomain?

“If you have the technical knowledge to adjust your DNS records and web server configuration, I recommend using subdomains for key content that your users would view as clearly separate from your main domain. You must change your DNS and web server configuration so that web users are properly directed to the proper page(s). For example, if you don’t make these changes, typing “” would send the user to “” and not the actual subdomain site.

“Good candidates for subdomains would be a blog, a documentation or support site, a members-only site, or a webmail system. I will say that putting a blog on a subdomain as opposed to in a subdirectory is a hotly debated topic from a search engine perspective.

“If you have content that is clearly part of the core message and functionality of your website, I would put it in a subdirectory.”

Are there search engine implications for one method or the other?

“Google has changed how it views subdomains. Google now views the subdomain as part of the main domain and not as a separate entity, which means the SEO implications of where you put your content are not as crucial as the quality of the content itself.

“There is a key question as to how Google assigns authority to a site and whether moving content to a subdomain will dilute the main site’s authority or give you a stronger overall level of authority. This topic is debated in SEO circles. Subdomains can keep some of your link authority, but you will want to be conscious about building a strong link structure between the main domain and subdomain and put some good content on the site.

“If SEO is your key consideration, there likely is a benefit for building a main domain with a lot of content. So, if you have no content to speak of beyond your products, putting your blog in a subdirectory would be a good idea (and make sure that you have strong cross-links to the rest of your site). If you already have lots of content on your site, and you want to establish a different tone, look, and message with your blog, a subdomain or separate domain would make sense.

“Note it will do you more harm than good to create a subdomain with the same content as your main domain, and Google specifically warns against doing this in its Webmaster Guidelines. The engineers at Google (and Bing) are smart and getting smarter. Ultimately if you put valuable, unique content on the web that is well-linked, you will be rewarded.”

What about SSL certificates and security issues?

“If you need to utilize SSL for the content that is specifically going to be on the subdomains, then you will be looking at an added cost, and subdomains might not be the best choice for you. An SSL certificate is tied to a specific, fully qualified domain name (FQDN). So if you want to use, you will need a separate certificate (or wildcard certificate) for that subdomain. The more economical solution would be to utilize subdirectories off of your main domain.”

How do you advise your clients to create subdomains?

“Overall, there is a positive branding aspect to utilizing subdomains. Just as a .com domain has a stronger pull and is more memorable than other top-level domains, deploying multiple subdomains can create a strong impact for your business and clearly segment different parts of your operation.

“You can combine subdomains with redirects to set up clear and consistent addresses for your users like:


“You can even use subdomains as a concise URL for print advertising that are easy to track in your analytics program.”

Final thoughts?

“If you have no idea how to configure your web server and DNS records, you will probably do fine to stick with subfolders and you will be on solid ground from an SEO perspective. But if you have the ability to configure DNS and site redirects, you can gain more control over your content and your messaging in certain situations with the use of subdomains. You will also be able to develop some advanced technical implementations that have a related address to your main domain but from a technical perspective can be completely separate.”

PEC Staff
PEC Staff
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