Subdomain vs subfolder

There is often confusion in the seo world between subdomain and subfolders. This post shall explain the difference.

Root domain

This is the domain that you buy from the hosting company eg or

This is a domain which is part of the root domain. eg

Also called folders are separate sections of the root domain. For example

What does Google say?
Google has viewed subdomains in the past as completely separate entities from the primary domain. Google uses what it calls “host crowding” where it returns up to two results from a single domain on a search engine results page (SERP) (with the second one indented). As subdomains are treated as totally separate, a single domain could get more than two listings on a Google SERP, through its subdomains. However, in December 2007, Google made a change announcing that subdomains would be more closely associated with the primary domain — not to the point of being viewed as a subdirectory, but not so completely separate. You can see more about this on Matt Cutt’s blog

If you are building your blog on a subdomain so, it may not get any benefit from its root domain and any links you get will flow back to that subdomain and not to Therefore you should set up the blog as a subfolder and when you get any external links, it will flow back to the root domain.

Rand Fishkin goes into a lot of detail about subdomains vs subfolders.

When do you use a subdomain?

– If your blog is separate to your services or if your cms does not allow you to add blogging software to the root domain.
– If you already have two pages from your main domain ranking for a search term. Google will show a maximum of two URLs on a given search page but may show more for a root domain if there are multiple subdomains.
– If you have keyword you want to rank for and you are doing link building for that domain.

When do you use subfolders/subdirectories?
– If you want to organise your site into different sections with descriptive URLs. This is also an easy way to grow your site.
– Adding subfolders allows you to build your site and add new content in a search friendly way.
– It is easier to use subfolder than subdomains due to the url structure as it is all under one domain.

And finally, there are some companies that set up a completely separate site to their main site.
When should you use a microsite?
– If you have a brand new product or service that will be eventually sold off.
– If you do not want the product or service to be associated with your site.

Having a microsite is like starting from scratch. There is no trust, authority, ranking power so you will need to spend a lot of time building up trust and authority.

I hope this post has cleared up some of the confusion regarding subdomains vs subdirectories. If you have any comments or questions, please get in touch.

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