Subdomain
A subdomain is a separate section of a website placed before the root domain in the URL. In blog.example.com, "blog" is the subdomain — and Google may treat it as a distinct site from the main domain.
A subdomain is a separate section of a website placed before the root domain in the URL. In blog.example.com, "blog" is the subdomain — and Google may treat it as a distinct site from the main domain.
Why It Matters
The choice between subdomain and subdirectory directly impacts SEO. Google crawls and indexes subdomains separately, so link equity may not automatically flow between the main domain and subdomain. This is why most SEO practitioners recommend subdirectories for blogs and content sections.
Subdomain vs. Subdirectory
| Aspect | Subdomain | Subdirectory |
|---|---|---|
| URL format | blog.example.com | example.com/blog |
| Google treatment | May crawl as separate site | Part of main site |
| Link equity | Can be diluted | Consolidated under main domain |
| Domain authority | Must build separately | Shares main domain authority |
| Management | Requires separate setup (DNS, SSL) | Unified under one domain |
Google's John Mueller stated both approaches are fine for search, but in practice subdirectories are generally preferred for SEO due to authority consolidation.
When Subdomains Make Sense
- Distinct services: When running a fundamentally different product (e.g.,
support.example.com) - Multi-region sites: When regions need independent operations (e.g.,
kr.example.com) - Technical separation: When different CMS or server environments are required
- Massive sites: When managing crawl budget across millions of pages
When Subdirectories Win
- Blog/content hub:
example.com/blog(most common use case) - Product categories:
example.com/products - Authority concentration: When consolidating all link equity under one domain
Sources: