What is a subdomain

Subdomain meaning for SEO

For technical SEO, a subdomain is a separate hostname that search engines crawl and report on apart from the main site. Unless you set up a domain-wide property, Google Search Console has you verify a subdomain as its own property. Its robots.txt file also sits at its own root. Teams put content on a subdomain when it runs on different software, such as a help center or a web shop. Before you plan keywords for a section of your site, check which hostname it's on.

How a subdomain works

A subdomain adds one more label to a domain name, and DNS can send that label to any server. Domain names read from right to left. In shop.example.com, ".com" is the top-level domain and "example" is the name you registered. The "shop" label in front is the subdomain. You create it for free in your DNS settings and can nest labels, as in eu.shop.example.com.

Subdomain vs domain

A domain is the name you register and renew each year, and a subdomain is a free extension of it that you manage from the same account. Whoever controls example.com controls every subdomain under it. Browsers also keep subdomains apart, so a cookie set on app.example.com doesn't reach www.example.com unless the site scopes it to the parent domain. And "www" is a subdomain too, which is why example.com and www.example.com can show different content when someone configures them badly.

Subdomain example

A software company at example.com has its marketing pages at www.example.com, while its product runs at app.example.com. The documentation is built with a separate tool and lives at docs.example.com. Because each subdomain can point to a different host, the docs team can switch platforms without touching the main site. Visitors see one brand, while search engines see three hostnames.

Subdomain SEO implications

Subdomains require extra work compared with subfolders, even though their ranking treatment is the same by default.

Does Google rank subdomains differently?

Google says the choice of structure isn't a ranking factor. John Mueller, a search advocate at Google, said in a Google Search Central video that "Google Search is fine with using either subdomains or subdirectories." He added that Google has to learn to crawl a new subdomain separately, which an SEO audit will show you,, but that this is "just a formality" for the first few days.

What a separate hostname costs you

You pay for a subdomain in upkeep. It needs its own sitemap and robots.txt file. Google treats it as part of the main site or as a separate site based on how tightly the two are linked. If the content doesn't need different software, a subfolder such as example.com/blog keeps everything on one host.

Subdomains in AI citations

AI assistants cite the exact URL an answer came from, so a subdomain shows up in the citation under its own hostname. When an assistant quotes your help center, the reader sees support.example.com. A visibility report that counts only example.com will miss those citations. Make sure your monitoring covers every hostname you publish on. Put your organization name on each subdomain and link back to the main site.

Subdomain in DNS

In DNS, a subdomain is a record in the parent domain's zone that maps the name to a destination. An A record points it to an IPv4 address, while a CNAME record points it to another hostname, which is how most hosted tools connect. When a browser asks for docs.example.com, a resolver queries the domain's authoritative name servers and returns the matching record. Remove CNAME records for services you've shut down, because an attacker who claims the old target can take over the subdomain.

Related terms

Now that you know what a subdomain is, list every hostname your organization uses and check that each one sits in your Search Console account and your visibility reports. While you're at it, remove any DNS record that points to a service you no longer use.