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:

  • is a sub-domain of
  • is a sub-directory of
  • is a sub-domain of
  • is a sub-directory of

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:


However, the URL that Google prefers to see is the one in the middle, i.e., 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