Subdomain SEO

Definition

Subdomains are separate hostname prefixes of your root domain: blog.example.com, support.example.com, shop.example.com. Subdirectories are paths within your root domain: example.com/blog, example.com/support, example.com/shop. From Google's perspective, subdomains can be treated as separate sites — they are separately crawled, separately evaluated for authority, and links between them are weighted somewhat like external links rather than internal links. This means content on blog.example.com generally does not directly benefit from the authority of example.com in the same way that example.com/blog would. The exception is when the subdomain has its own substantial authority — a high-traffic docs.example.com with thousands of inbound links will rank independently.

Why it matters for SEO

Moving content from a subdomain to a subdirectory is one of the most reliable SEO wins for growing sites. The consolidated authority of all content under example.com lifts ranking potential for every page. Subdomains are appropriate when the content is genuinely distinct (a completely separate product serving a different audience, a staging environment, an app at app.example.com that is not content-focused). They are not appropriate when the motivation is organisational convenience rather than genuine product distinction — that separation has an SEO cost.

How DeepSEOAnalysis checks this

The audit detects when a site's blog, help centre, or store lives on a subdomain rather than a subdirectory, and flags it as a consolidation opportunity with its estimated internal link impact. It also checks for www vs non-www canonical consistency — both versions must 301-redirect to the same canonical version with a self-referencing canonical tag.

Useful tools and resources

• Full technical SEO audit