A Record vs CNAME: Which DNS Record Should You Use?

A records and CNAME records both make a hostname resolve to something usable — but they do it in different ways, they have different limitations, and picking the wrong one for a given hostname causes problems that are entirely avoidable once you know the rule.

The Core Difference

	A Record	CNAME Record
Points to	An IP address directly	Another hostname
Resolution	Single lookup	Follows the target hostname, then resolves that
Usable at domain root?	Yes	No
Can coexist with other records at the same name?	Yes	No — must be the only record there
Typical use	Root domain, direct server IP	Subdomains, CDNs, third-party services

An A record is a direct answer: example.com → 192.0.2.10. A CNAME is an instruction to keep looking: www.example.com → example.com, and only then does resolution continue on to find example.com's actual address.

Why You Can't Use a CNAME at the Root Domain

This is the single most common reason people end up choosing between the two. A domain's root — example.com itself, not a subdomain — always has to carry an SOA record and at least two NS records, since every zone requires them. But a CNAME record can't coexist with any other record type at the same name; if a name has a CNAME, that's the only thing allowed there. Put those two requirements together and a literal CNAME at the root is simply invalid — most authoritative nameservers will reject it outright.

That's why root domains almost always use an A (and usually an AAAA) record instead. Providers who want to offer CNAME-like convenience at the apex anyway do it with a workaround — commonly branded CNAME flattening, ALIAS, or ANAME — where the provider's own infrastructure resolves the target hostname on your behalf and publishes a plain A/AAAA record to the rest of the internet.

When to Use an A Record

• At your domain's root/apex, since a CNAME isn't an option there.
• When you're pointing at a specific IP address you control and don't need it to automatically follow another hostname.
• When the hostname needs to carry other records alongside it — a CNAME can't share a name with a TXT record, for instance, but an A record can.

When to Use a CNAME

• For subdomains that should always match another hostname — www pointing at the root domain is the classic case.
• When pointing at a CDN, hosting platform, or SaaS provider using the domain name they give you, rather than an IP address that could change without notice on their end.
• Anywhere you'd otherwise have to manually update an IP address every time the target infrastructure changes — the CNAME keeps working automatically as long as the target hostname's own records stay current.

Example Configurations

A record at the apex, CNAME for www:

example.com.       A      192.0.2.10
www.example.com.   CNAME  example.com.

Subdomain pointed at a third-party service:

app.example.com.   CNAME  customer-123.saas-provider.net.

Decision Table

Situation	Use
Root domain (example.com)	A (and AAAA)
www subdomain	CNAME to the root, or its own A record
Subdomain pointed at a CDN/SaaS provider	CNAME
Hostname needs a TXT/MX record too	A (CNAME can't share the name)
Direct, stable IP you manage yourself	A

How to Check Which One a Hostname Uses

ProURLMonitor's free DNS Records Checker looks up both A and CNAME records (along with AAAA, MX, TXT, NS, and SOA) for any hostname, so you can confirm exactly which one is configured before making a change. For the full picture on CNAME mechanics and its limitations, see our CNAME record guide.

Frequently Asked Questions

What's the core difference between an A record and a CNAME record?

An A record maps a hostname directly to an IPv4 address. A CNAME record maps a hostname to another hostname, which then gets resolved in turn to find the actual address. An A record is a direct address lookup; a CNAME is one extra hop of indirection.

Can I use a CNAME record instead of an A record for my root domain?

No — a domain's root (apex) is required to carry SOA and NS records, and a CNAME can't coexist with any other record type at the same name, so a literal CNAME at the root is invalid. Root domains use an A (and usually AAAA) record instead, or a provider-specific apex workaround like CNAME flattening, ALIAS, or ANAME.

Is a CNAME record slower than an A record?

Marginally, on an uncached lookup. Resolving a CNAME requires following it to its target hostname and then resolving that hostname's own address record — one extra step compared to an A record, which returns an address directly. Once cached, the difference is negligible for most practical purposes.

When should I use an A record instead of a CNAME?

Use an A record at your domain's root, and anywhere you're pointing directly at a specific, stable IP address you control. A records are also the only option when a hostname needs to carry other record types alongside it, since CNAME can't share a name with anything else.

When should I use a CNAME instead of an A record?

Use a CNAME for subdomains that should always match wherever another hostname points — most commonly www pointing at the root domain, or a subdomain pointed at a CDN, hosting platform, or SaaS provider's own domain, so you're not stuck manually updating an IP address every time that provider's infrastructure changes.

Does changing from an A record to a CNAME (or back) affect anything else?

It can. Because a CNAME can't coexist with other records at the same name, switching a hostname to a CNAME means removing anything else configured there, such as a TXT record used for verification. Check what else lives at a hostname before switching its record type.