Subdirectory vs. Subdomain for SEO

If you plan to install a wiki or blog onto your site – or if you have done so already – you probably are faced with a choice of installing this software in a sub-domain or a sub-directory. In other words, you can choose to install your blog or wiki one of these ways:

  • blog.domain.com is a sub-domain of domain.com
  • domain.com/blog is a sub-directory of domain.com
  • wiki.domain.com is a sub-domain of domain.com
  • domain.com/wiki is a sub-directory of domain.com

Google tends to treat sub-domains like as a separate domain whereas it considers sub-directories as a deeper extension of a single domain. The difference is important because sub-directories tend to dilute your inbound link juice across multiple domains where as sub-directories tend to concentrate the link juice down a single domain name.

100% link juice (concentrated)

By the way, at a recent advanced search engine marketing conference, a representative from Google declared that directories should end with a forward slash (/) instead of open-ended. For example, the following three URLs all point to the same spot:

  1. www.inQbation.com/blog
  2. www.inQbation.com/blog/
  3. www.inQbation.com/blog/index.php

However, the URL that Google prefers to see is the one in the middle, i.e., www.inQbation.com/blog/. This helps with the process of canonicalization and helps them correctly resolve URLs.

How do you say canonical or canonicalization?

If you have already set up a blog or wiki as a sub-directory then it’s not too late to make the change. However, you have to be very careful to set up 301 redirects, dot htaccess files or link rel=canonical or else you will not get the link credit from existing inbound links. Google has stated in their guidance to webmasters that if you plan to move a sub-domain to a sub-directory then you should use a 301 redirect to it knows to honor the existing link juice and pass it on to the new sub-directory.

YouTube Video: Canonical / Canonicalization