Folders or sub-domains in SEO

Whilst analyzing a website yesterday which was on a sub domain, I wondered if a sub domain was the best way forward for the client, or whether the client should simply add folders to his existing domain.

The argument – Is it better to have one high-level domain with each sub site located in folders eg:www.mysite.co.uk/subsite, or a sub domain structure such as subsite.mysite.co.uk?

Argument for folders

Content placed within folder structures are seen by the search engines as part of the same site, the more sub sections in your site the more content your site will have. And we all know that the search engines particularly Google love sites that are rich in content. In addition adding subsections to sites allows the page rank to spread throughout the site, especially if you have a strong internal link structure, or run an e-commerce store.

Also it is easier to create and maintain folders within a site, than it is to create and maintain sub domains, this is due to each sub domain being built as though it is a different site.

Argument for sub domains

Search engines view sub domains as completely different sites, therefore any links between the domains will carry a greater weight as they are seen as external links. Although getting each sub domain ranked highly in the search engines is costly. Good internal linking within folder structures will also create quality inbound links without the need to create a new sub domain.

Sub domains are normally created to be specific and concentrate on a particular subject, meaning each sub domain can be submitted to its relevant directory. It is more difficult to submit parts of the same website to different categories as this can be seen as spam and breach submission rules.

Conclusions

As content is so important in obtaining great rankings, I would tip folders to be the best option to choose, it is however important that if you choose this option you have a strong internal linking structure to spread the power. However if you have loads of content, or marketing issues such as a change of brand, then sub domains may be the best option. Do remember though creating a sub domain is more time consuming than simply creating a new section on your existing site.

Paul
SEO Programmer