Glossary

Subdomain

Definition: A prefix added to a root domain to create a distinct address for a specific section or service of a website.

A subdomain is an extension of a domain name that precedes the root domain, separated by a dot. For example, in blog.example.com, blog is the subdomain. Subdomains can point to different servers, run different applications and be managed independently in DNS.

Common Subdomain Uses

  • www — Traditional web prefix for the main website
  • blog — Separate blog platform
  • shop — E-commerce store (often on a different platform like Shopify)
  • app — Web application
  • mail — Mail server
  • api — API endpoint
  • staging or dev — Test environments
  • cdn — Content delivery network assets

Creating a Subdomain

Add an A record (or CNAME) in your DNS settings:

blog.example.com    IN    A    192.0.2.10
shop.example.com    IN    CNAME    example.myshopify.com

Subdomain vs Subdirectory for SEO

This is a common SEO debate:

  • Subdirectory (example.com/blog) — Consolidates all link equity under one domain. Simpler for smaller sites.
  • Subdomain (blog.example.com) — Treated as a separate entity by Google. Can be on separate servers. Better when the section is technically independent.

Google says it treats subdomains and subdirectories equivalently, but many SEO practitioners prefer subdirectories for blog content.

SSL and Subdomains

A standard SSL certificate covers only the root domain and www. A wildcard certificate (*.example.com) covers all first-level subdomains.

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