Subdomains and subdirectories are two ways to decide where different sections of a website will sit.
A subdomain comes before the main domain. For example, blog.example.com places the blog on a subdomain.
A subdirectory keeps the section after the main domain, such as example.com/blog/.
To a visitor, the difference may seem small. Behind the website, however, the two setups can be managed quite differently.
What Is a Subdomain Used For?
Businesses often use subdomains when a section needs to operate somewhat independently from the main website. Examples include booking systems, customer portals, help centres, web applications or platforms built using different software.
Google can find and rank pages on a subdomain, just as it can pages elsewhere on the web. The practical issue is usually management. A separate setup can mean more work for tracking, technical checks and ongoing SEO.
What Is a Subdirectory Used For?
A subdirectory keeps related pages together under the same domain. A website might have /blog/, /services/, /products/ and /locations/.
This arrangement is common for business websites because everything remains within the same site structure. Adding new sections and monitoring their performance can also be easier when they sit under one domain.
Which Is Better for SEO?
Neither option comes with an automatic ranking advantage simply because of its URL format.
The choice is more about what the section is for. If a blog, service area or collection of pages clearly belongs to the main website, keeping it in a subdirectory is often the more practical setup.
A subdomain is useful when there is a genuine reason for separation, particularly when the section uses different technology or serves a separate function.
For SEO, the bigger concern is whether Google can crawl the pages, understand how they relate to the rest of the site and find useful content on them. The URL structure itself is only one part of that.