subdomain

A subdomain is a domain that forms part of a larger domain in the Domain Name System. It is created by adding a prefix to an existing domain name, such as blog.example.com, which is a subdomain of example.com. Subdomains reside within the DNS hierarchy under their parent domain and can be managed separately from the parent zone.

DNS configuration: Subdomains are established by adding DNS records for the subdomain or by delegating a separate DNS zone to the subdomain. A subdomain can point to its own IP address with A or AAAA records, or alias to another name with a CNAME. It can also carry its own mail exchange (MX) and other records, and may be hosted on a different server than the parent domain.

Use cases: Subdomains are used to host distinct services (web apps, blogs, mail, storefronts), separate environments (development, staging), or to organize content by region or language. They are also common in multi-tenant setups and in enterprise networks. A subdomain is not the same as a subdirectory (for example example.com/blog/), which is a path within the same domain and is served from the same hostname.

Operational considerations: Wildcard subdomains (*.example.com) can catch requests for non-existent subdomains. DNS changes propagate with varying latency. Search engines may treat subdomains as separate properties, affecting indexing and ranking; many organizations track them as distinct sites or use canonicalization to unify them.