Skip to content

Subdomain

A subdomain is a domain name created beneath another domain and can be used to route different services or parts of a website independently.

A subdomain is a domain name that exists beneath another domain within the DNS hierarchy.

For example:

shop.example.com

is a subdomain of:

example.com

Common Examples

Subdomains are commonly used for:

  • www.example.com
  • shop.example.com
  • app.example.com
  • docs.example.com
  • members.example.com
  • api.example.com

Each can point to completely different infrastructure.

Subdomain vs. Path

Consider:

shop.example.com

versus:

example.com/shop/

The first uses a subdomain.

The second uses a URL path.

Your URL Structure term covers path decisions in more detail.

These approaches can look similar to users while having very different infrastructure underneath them.

How Subdomains Work

The subdomain can have its own DNS records.

For example:

shop → CNAME → hosted-store.example
api  → A     → 192.0.2.20

It may even have its own separately delegated DNS Zone in more advanced architectures.

Why It Matters

Subdomains allow one registered domain to support multiple systems.

A company can run:

  • Main marketing site on one platform
  • Store on another
  • Application elsewhere
  • API on different infrastructure

without registering a new domain for each service.

SEO Considerations

Subdomains and URL paths should be chosen based on architecture and operational requirements rather than myths about automatic rankings.

Technical SEO considerations still apply to any public indexable website content regardless of which approach is chosen.

Common Problems

Common problems include:

  • Forgotten subdomains
  • Old services remaining publicly reachable
  • TLS Certificate not covering the hostname
  • DNS records pointing at retired infrastructure
  • Similar content duplicated across root and subdomain
  • Separate platforms with inconsistent navigation
  • Analytics & Measurement not configured across the journey

How to Improve

Maintain an inventory of active subdomains.

For each one, document:

  • Purpose
  • DNS record
  • Hosting/service provider
  • Owner
  • Whether it is public
  • Whether it should be indexed
  • TLS/HTTPS status