Understanding Subdomains

In the domain name system, a subdomain is a dependent domain set up within the primary domain. For example, if you have the following URL for your site:

http://www.beautyproducts.com

You can set up a subdomain called cosmetics, so you URL becomes:

http://cosmetics.beautyproducts.com
 

Why People Set Up Subdomains

Websites often create subdomains in order to segregate sections of web pages to create a virtual “site within a site.” In the example, the cosmetics subdomain could be used to hold information about specific beauty products that you decided not to include within your main site navigation scheme.

The subdomains are useful in different environments:

Some social media sites automatically create a subdomain for each person who signs up:

http://yourname.wordpress.com

Some companies create subdomains for their different employees:

http://susan.beautyproducts.com

Other sites set up subdomains as a way of separating their content into different categories, like this

http://skincare.beautyproducts.com
http://haircare.beautyproducts.com
http://fragances.beautyproducts.com

We don’t recommend organizing the bulk of your site content by subdomains, for several reasons we discuss next.
 

How Search Engines View Subdomains

Search engines consider subdomains to be entirely separate sites. Subdomains endanger your search engine optimization because the search engines do not see the subdomain as part of your main site. They also do not see any connection between your various subdomains. You are taking all the benefit of your inbound links and all of your content, and dividing them across several separate web properties. This is, in general, a bad idea. If you did it anyway, you would need to optimize each subdomain for the search engines separately.

You benefit from using subdomains on your web site only in the following cases:

Large brands. Huge companies can successfully use subdomains to separate their content. They have many pages about each division or product, so each subdomain ranks well on its own. Also, it benefits users to have the well-known brand name in every URL (it confirms that the pages belong to that company). Finally, the multiple subdomains could yield multiple results on a search results page, if several come up for the same keyword.

Totally unrelated content. If you wanted to start a side business selling fashion accesories, you wouldn’t want to dilute your beauty products web site with pages on earrings and necklaces. You could register an entirely different domain for this, or you could handle this new business as a subdomain of your main web site. Subdomains are convenient for marketers who want to use a single main domain and then create separate areas for non related products.

Blog sites provide another example of subdomains. Your blog would be assigned the yourname.wordpress.com subdomain and would contain your writing whithout any relation to other people’s blog.

Secure content. If part of your website content is only available through a logon, it could be set up as a subdomain. Search engines don’t spider content behind a logon, so having it in a separate subdomain doesn’t matter for your SEO efforts anyway.

International sites. Targeting different countries can be done using subdomains. If you don’t have the resources to buy www.beautyproducts.co.uk, or if that domain is already taken, you can target the UK through uk.beautyproducts.com instead.

Your site needs lots of relevant content to reach the front pages of the search results. Splitting up that content into separate subdomains is self-defeating. If you are currently using subdomains as a way of organizing your site content, stop it. Use other techniques like siloing.

You can learn more about domains, subdomains and SEO following the Mastermind Course Curriculum