DNS & Glossary

CNAME record (Canonical Name)

An alias that points one hostname at another canonical name — useful for pointing subdomains at a CDN or platform without hard-coding IPs.

What it stores

A CNAME maps a name to another name rather than to an address. The resolver then looks up the target's A/AAAA records. It is ideal for www → platform hostnames and CDN endpoints, so the provider can change IPs without you editing your zone.

ZONE FILE
www.example.com.   300   IN   CNAME   example.com.
assets.example.com. 300  IN   CNAME   d1234.cloudfront.net.

No CNAME at the zone apex

You cannot put a CNAME on the root domain (example.com) because it coexists with mandatory SOA/NS records. Use A/AAAA, or a provider's ALIAS/ANAME/flattening feature instead.

Why it matters

  • It decouples your names from provider IPs, so CDN/platform IP changes need no zone edits.
  • Misusing it at the apex or chaining CNAMEs adds latency and can break resolution.

Common mistakes

  • Attempting a CNAME on the apex domain, which is invalid.
  • Long CNAME chains that add extra lookups and slow resolution.

How WebInspect checks this

  • The Network Inspector follows CNAME chains and reports each hop to the final address.