What it is
Domains have a hierarchical structure that consists of both subdirectories and subdomains, which can sometimes get very confusing. Subdomains are addresses that exist under your primary domain and are commonly used to create new addresses that host different or specific kinds of content. This is different than a subdirectory, which is content that exists on your primary domain but underneath the main page /directory. For example:
- Primary domain
Why it matters
Search engines treat subdomains almost as completely separate entities. SEO value won’t necessarily flow between subdomains and the root domain, or vice-versa. When building out new content, it’s therefore well worth considering whether it should be housed on a subdomain or subfolder.
Sometimes it’s even beneficial to move a subdomain to a subfolder so it can share SEO benefit with the rest of the site.
What to do
- Consider whether a subdomain is the best place for content with SEO value
- In general, we advise against using subdomains for content with SEO value unless absolutely necessary.
- Ensure each subdomain has its own robots.txt file
- SEE Also: Analytics: cross-domain & subdomain tracking.