Matt Cutts’ SEO blog discusses different ways Google interprets Sub-Domains and Folders. What’s important is how your Google PageRank may be affected by setting up a new blog on a sub-domain versus a new folder.
Why Sub-Domains are Better for Google PageRank
If your site has a good PageRank, then the new content you add, including pages, images, and videos, is given the same weight of the existing domain.
This means it ranks the same as the parent site after it has been indexed.
With a subdomain, you are essentially starting from scratch. You need to work up and create the same amount of weight for each sub-domain.
- Google interprets a sub-folder as a subset of a site – and awards it the same PageRank as the parent.
- Google interprets a sub-domain as a unique site – you create the PageRank as for any new site.
However, using keywords in the sub-domain URL may increase traffic to the site as Google will identify these keywords and use them to index the pages.
How Link Weight Works
The way Google gives weight to links is also considering. For example, Google considers a link from
BUT… this link does not carry much weight in terms of SERPs.
Now, let’s look at how Google treats links between domains and subdomains.
From what I’ve seen, Google does not treat links to and from subdomains as internal links.
Rather it treats sub-domains as separate domains.
This means that a link from
is fully weighted as an offsite link.
See article on Google Webmaster Tools.
Google PageRank & Root Domains
Google’s algorithm has changed over the years and now ‘seems’ to treats web pages independently. This means that unique web page can outrank the home page as web pages can be allocated unique PageRank values.
Another point is that the closer a folder is to the root, the more it gets credited with PageRank values.
Search engines appear to give more weight the closer you are to the root domain.
This means that
The ‘city’ folder will get less credit as it is further from the root.
Subdomains are treated as root, carry all the weight of root, and therefore start out with more weight right out of the gate.
Submitting to Web Directories
One problem for webmasters is that if you submit a site to a web directory – with a folder – it will probably get rejected.
However, if you submit a sub-domain, it is usually accepted as it’s seen as a unique standalone site.
Web Directories refuse Folders as they see this as a ‘deeplink’ to the home page URL. Sub-domains such as news.bbc.co.uk are accepted as unique sites.
Search Engine Results Position
Google, and other Search Engines, give your domain one or two listings in the search results.
Your other results are indented under the root domain. If your site is designed correctly, it will show them in logical order, which is for another post.
What this means is:
- Using Folders – Your website will get one listing per search. Your folders will be indented in the listings under the root.
- Using Sub-Domains – Your website get more listing per search as each Sub-Domain is interpreted as a unique site.
Note: If you use folders, you only get 2 results in the SERPs. If you sub-domains, you can potentially dominate the results page with different sites.
In most cases, using a sub-folder is best as you ‘micro-site’ is under the umbrella of the main site.
The downside is that the more pages you add, the less PR is spread across your site. My advice is to do split testing and check the results in the SERPS.
What else would you add?
PS – the screenshots were taken from the GoDaddy Web Hosting Control Panel