What is CNAME Record?

A DNS record that creates an alias pointing one domain name to another, commonly used for subdomains and CDN configuration.

CNAME Record (Canonical Name) - What It Means & How It Works

What is a CNAME Record?

A CNAME (Canonical Name) record is a DNS record type that creates an alias from one domain name to another. Instead of pointing directly to an IP address like an A record, a CNAME points to another domain name, which is then resolved to an IP address.

How CNAME Records Work

When you set up a CNAME:

www.example.com.    IN    CNAME    example.com.

The resolution process:

1. User requests www.example.com

2. DNS finds CNAME pointing to example.com

3. DNS then resolves example.com's A record

4. Final IP address is returned

This chain resolution means CNAME targets must eventually resolve to an A or AAAA record.

Common CNAME Use Cases

WWW Subdomain

Point www to your root domain:

www    IN    CNAME    example.com.

CDN Integration

Point your domain to a CDN endpoint:

cdn.example.com    IN    CNAME    d111111abcdef8.cloudfront.net.

Platform Hosting

Point to hosting providers:

blog.example.com IN CNAME yoursite.wordpress.com.

shop.example.com IN CNAME shops.myshopify.com.

SaaS Applications

Connect subdomains to SaaS platforms:

docs.example.com IN CNAME example.gitbook.io.

status.example.com IN CNAME stats.uptimerobot.com.

CNAME vs A Record

Scenario	Use CNAME	Use A Record
Root domain (@)	❌ Not allowed	✅ Required
Subdomain to static IP	Either works	✅ Direct
Subdomain to provider	✅ Preferred	❌ IP may change
CDN configuration	✅ Typical	Varies
Load balancing	❌ Can't have multiple	✅ Multiple IPs

Why Root Domains Can't Use CNAME

The DNS specification (RFC 1034) prohibits CNAME records from coexisting with other record types at the same name. Since root domains need SOA and NS records, they cannot have CNAME records.

Solutions for root domain aliasing:

ALIAS/ANAME records: DNS provider-specific pseudo-records
CNAME flattening: Cloudflare and others resolve CNAMEs to A records
Redirect www to root: Use CNAME for www, redirect to @ at application level

CNAME Chains

CNAMEs can point to other CNAMEs (chaining):

blog.example.com → myblog.host.com myblog.host.com → lb-1234.hosting.com

lb-1234.hosting.com → 203.0.113.50 (A record)

While valid, chains add latency. Most DNS providers limit chain length to prevent infinite loops.

CNAME Record Configuration

Basic Syntax

subdomain    IN    CNAME    target.domain.com.

Important: The target domain should include a trailing dot (.) to indicate it's fully qualified. Without it, some DNS servers append the origin domain.

TTL Considerations

CNAME TTLs affect how quickly changes propagate:

www    300    IN    CNAME    example.com.

Lower TTLs (300 seconds) allow faster updates; higher TTLs reduce DNS queries.

Checking CNAME Records

Using dig:

dig www.example.com CNAME ; ANSWER SECTION:

www.example.com. 300 IN CNAME example.com.

Full resolution trace:

dig +trace www.example.com

Common CNAME Issues

CNAME at Root Domain

example.com    IN    CNAME    other.com.    ; INVALID

This breaks email (MX records) and other services.

CNAME with Other Records

blog.example.com IN CNAME host.com.

blog.example.com IN MX mail.host.com. ; INVALID

A name with a CNAME cannot have other record types.

Missing Target Records

If the CNAME target doesn't resolve, your subdomain won't work either. Verify targets are valid before configuring CNAMEs.

Best Practices

1. Use CNAMEs for third-party services: Let providers manage IP changes

2. Avoid deep chains: Each hop adds latency

3. Don't CNAME the root: Use A records or ALIAS

4. Include trailing dots: Ensure fully qualified target names

5. Monitor CNAME targets: External changes can affect your site

CNAME Record (Canonical Name)