Record Types: A, CNAME, Alias, and More
~10 min read
The common DNS record types you'll actually use, and Route 53's special Alias extension.
A records map a name to one or more IPv4 addresses directly — the most basic record type. AAAA records do the same for IPv6. MX records specify mail servers for a domain (used for email routing, not web traffic). TXT records hold arbitrary text, commonly used for domain verification (proving you own a domain to a third-party service) and email security policies like SPF/DKIM.
CNAME records alias one name to another name (not an IP directly) — resolving a CNAME requires an additional lookup to resolve the target name to an actual IP, and per the DNS specification, a CNAME cannot coexist with any other record type at the same name, and cannot be used at a zone's apex/root.
Route 53's Alias record type is an AWS-specific extension that behaves like an A record externally (works at the zone apex, no extra lookup) but internally is a pointer to a supported AWS resource (ELB, CloudFront, S3 static website endpoint, another Route 53 record, and more) whose actual IP Route 53 resolves and keeps current automatically — this is why Alias is preferred over CNAME whenever the target is an AWS resource.
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Key points
- •A/AAAA: name to IPv4/IPv6 address directly
- •CNAME: name to another name, extra lookup, cannot be used at the zone apex
- •Alias (Route 53-specific): behaves like A at the apex, no extra lookup, auto-tracks AWS resource IPs
- •MX and TXT serve mail routing and verification/security purposes, not web traffic routing