What Is a Subdomain?
Anything left of the root dot: blog.yourdomain.com. It’s a separate hostname that can point to different servers, regions, or SaaS platforms while sharing the parent’s brand trust and SSL certificate wildcard.
SEO vs Technical Separation
Google treats subdomains as separate sites for ranking but shares some domain authority. Use them when content is distinct (shop, docs) and keep core marketing pages on the root domain.
Popular Use-Cases
- www – legacy CNAME flexibility behind CDNs
- shop. – points to Shopify or WooCommerce
- api. – dedicated server for rate-limited REST calls
- staging. – clone environment for QA
- help. – hosts knowledge-base Zendesk
Creating Subdomains
In registrar DNS or Cloudflare, add an A record named api pointing to IP, or CNAME shop → shops.myshopify.com. TTL 300 seconds for quick changes; raise to 14400 when stable.
Wildcard Certificates
A *.yourdomain.com SSL cert covers unlimited subdomains. Let’s Encrypt offers free wildcards via DNS-01 challenge. Automate renewal with Certbot and Cloudflare API token.
Content Isolation Benefits
If shop.domain.com gets hacked, api.domain.com on a separate VM remains unaffected. Subdomains give you blast-radius control without buying extra domains.
International Subdomains
Use uk.domain.com instead of buying .co.uk for lightweight localization. Hreflang tags can reference subdomains, consolidating backlink equity under one TLD.
Drawbacks to Watch
- Cookie isolation – root domain cookies don’t auto-apply, complicating SSO
- Analytics setup – need separate Google Analytics properties or cross-domain tracking
- Reputation bleed – blacklisted IP on one subdomain can tarnish root if shared
Management at Scale
Use Terraform or Cloudflare API to spin up staging-001, staging-002 programmatically. Tag instances in DNS with TTL 60 so they auto-expire after use, keeping DNS clean.
Deletion Policy
Stale subdomains can be hijacked via leftover CNAMEs pointing to expired SaaS accounts. Audit quarterly; remove unused records and rotate any tokens referenced in them.