DNS CNAME Record Lookup: Find Domain Aliases

A CNAME record (Canonical Name record) 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 hostname. This is commonly used for subdomains, CDN configurations, and custom domain setups for third-party services like email platforms, GitHub Pages, or Shopify stores.

How to Look Up CNAME Records

1. Enter the subdomain or domain — CNAMEs are most often set on subdomains (e.g., www.example.com or shop.example.com).
2. Select CNAME from the record type list — This filters results to canonical name records only.
3. Click Lookup — The tool returns the target hostname the CNAME points to.
4. Follow the chain if needed — A CNAME may point to another CNAME (chaining). The final target will be an A or AAAA record.

Example: Querying a CNAME Record

# Using dig
dig www.example.com CNAME

# Using nslookup
nslookup -type=CNAME www.example.com

# Example output:
# www.example.com.   3600   IN   CNAME   example.com.

# GitHub Pages custom domain example:
# www.mysite.com.   3600   IN   CNAME   username.github.io.

Why Check CNAME Records?

• Verify custom domain setup — Services like Netlify, Vercel, and GitHub Pages require a CNAME pointing to their infrastructure. Checking it confirms the setup is correct.
• Debug www vs. non-www issues — Many sites alias www to the root domain via a CNAME. If www is broken, the CNAME is usually where to look.
• Audit CDN configuration — CDNs like Cloudflare and Fastly often use CNAMEs to route traffic. A lookup shows where your traffic is being directed.
• Check third-party integrations — Email marketing platforms, helpdesk tools, and SaaS products often ask you to add a CNAME to verify ownership.

CNAME Restrictions

You cannot use a CNAME on a root (apex) domain — that is, you cannot set a CNAME for example.com itself, only for subdomains like www.example.com. This is a DNS specification limitation. Some DNS providers (Cloudflare with CNAME Flattening, Route 53 with ALIAS records) work around this for apex domains.

CNAME vs. A Record: When to Use Which

Use an A record when you know the exact IP address of your server. Use a CNAME when you want a subdomain to follow another hostname (especially useful when the target IP changes, such as with cloud services). If the target's IP changes, only the A record at the target needs updating — all CNAMEs pointing to it automatically resolve correctly.

Look up CNAME records instantly with the DNS Lookup tool — see where any subdomain is aliased.