What is the difference between a CNAME and an A record?

An A record points a hostname directly to an IPv4 address. A CNAME record points a hostname to another hostname, which is then resolved to find the IP address. Use an A record when you know the IP, and a CNAME when you want to follow another name such as a provider endpoint.

Can I use a CNAME on my root domain?

No. The DNS specification does not allow a CNAME at the zone apex because the apex must also hold records such as SOA and NS, and a CNAME cannot coexist with other records on the same name. Use an A record or a flattening record type like ALIAS at the apex instead.

Is a CNAME slower than an A record?

A CNAME can add a small amount of latency because the resolver must perform an extra lookup to follow the alias to its target name and then resolve that name to an IP address. In practice this is usually negligible thanks to caching, but a direct A record avoids the extra step.

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CNAME vs A Record

CNAME vs A Record

A records and CNAME records are the two most common ways to point a domain at something, and they are easy to confuse. An A record maps a name directly to an IP address; a CNAME maps a name to another name. The distinction matters because each has rules and trade-offs that decide which one you should reach for, and using the wrong one can break your apex domain or your email.

Quick answer

Use an A record when you have an IP address to point at, and a CNAME when you want one name to follow another name. A records are required at your root (apex) domain, where CNAMEs are not allowed. CNAMEs shine when you point a subdomain at a provider's hostname and want it to track that provider's IP changes automatically.

What an A record does

An A record maps a hostname directly to an IPv4 address. It is the most fundamental mapping in DNS:

www.example.com A 93.184.216.34

Because it returns the IP directly, an A record involves no extra resolution step. The trade-off is that if the underlying server's IP changes, you must update the record yourself. A records are also the standard way to point your apex domain, where CNAMEs are forbidden.

What a CNAME does

A CNAME record (canonical name) aliases one hostname to another. Instead of an IP, it returns a target name, and the resolver then looks that name up:

www.example.com CNAME myapp.herokudns.com

This is ideal for pointing a subdomain at a managed service. If the provider changes the IP behind myapp.herokudns.com, your www follows along with no action from you. A CNAME must be the only record on its name, so you cannot add other records, such as MX, alongside it.

Key differences

Apex restriction. A records work at the root domain (example.com); CNAMEs are not permitted there because they cannot coexist with the apex SOA and NS records.
Extra lookup. A CNAME adds one resolution step to follow the alias, whereas an A record returns the IP immediately. Caching usually hides this.
Maintenance. A CNAME tracks its target's IP automatically; an A record must be updated by hand if the IP changes.
Coexistence. A CNAME must be the only record at its name; an A record can sit beside other record types.
Chaining. A CNAME may point to another CNAME, but long chains add lookups and are best avoided.

When to use which

Reach for an A record at your apex domain, when you control the server and its IP, or when the name must also carry other record types. Reach for a CNAME on subdomains that point at a third-party service whose IP you do not control, so the mapping stays correct as the provider changes infrastructure.

If you need CNAME-style behaviour at the apex, that is exactly what flattening record types solve; see ALIAS records.

At a glance

	A record	CNAME record
Points to	An IPv4 address	Another hostname
Allowed at apex	Yes	No
Extra lookup	No	Yes
Tracks target IP changes	No	Yes
Can coexist with other records	Yes	No