Free CNAME Lookup Tool — Check CNAME Records for Any Domain
A CNAME record is an alias — it points one domain name to another instead of directly to an IP address. When your subdomain isn't resolving or your custom domain setup isn't working, a CNAME check is step one.
Check CNAME records now: Our free DNS Lookup Tool shows CNAME records alongside all other record types for any domain.
What Is a CNAME Record?
CNAME (Canonical Name) is a DNS record that creates an alias from one domain to another. Instead of resolving to an IP address directly, a CNAME tells the resolver to look up a different domain name.
Example:
www.example.com. 3600 IN CNAME example.com.
blog.example.com. 3600 IN CNAME mysite.netlify.app.
shop.example.com. 3600 IN CNAME shops.myshopify.com.
When someone visits blog.example.com, the resolver sees the CNAME, then looks up the A/AAAA records for mysite.netlify.app and connects to that IP.
How to Look Up CNAME Records
Method 1: DNS Lookup Tool
Enter any domain or subdomain in our DNS Lookup Tool. If a CNAME exists, it appears in the "Address Records" section. If the domain has direct A/AAAA records instead of a CNAME, those are shown instead — you can't have both.
Method 2: Command line
# Check for CNAME
dig www.example.com CNAME +short
# Output: example.com.
# Trace the full resolution chain
dig www.example.com A +trace
The +trace flag follows the entire resolution path, showing each CNAME hop and the final A record.
When You Need CNAME Records
wwwsubdomain —www.example.com→example.com- Custom domains on SaaS platforms —
blog.example.com→yoursite.wordpress.com - CDN setup —
cdn.example.com→d1234.cloudfront.net - Custom domain for GitHub Pages —
docs.example.com→username.github.io - Email provider verification — DKIM records are often CNAMEs to the provider's key servers
The CNAME Rules
A CNAME cannot coexist with other records
This is the most important CNAME rule. If blog.example.com has a CNAME, it cannot also have A, AAAA, MX, TXT, or any other record at that exact name. The CNAME "owns" the name exclusively.
This is why you can't put a CNAME on your root domain (example.com) if you also need MX records there (you do, for email). Solutions:
- Use an A/AAAA record at the root, CNAME only on subdomains
- Use your DNS provider's ALIAS/ANAME/CNAME flattening (Cloudflare, Route53, and others support this)
CNAME chains should be short
A CNAME can point to another CNAME, creating a chain. But long chains slow down resolution and increase the chance of failure. Keep it to one hop when possible.
CNAME targets must resolve
If blog.example.com points to mysite.netlify.app and that hostname doesn't resolve, your subdomain is broken too. When a hosting provider changes their CNAME target, you need to update yours.
Troubleshooting CNAME Issues
Subdomain doesn't resolve
- Check the CNAME exists: Use our DNS Lookup Tool to verify
- Check the target resolves: Look up the CNAME target separately — does it have A records?
- Check for conflicts: Is there an A record AND a CNAME at the same name? Remove one.
- Check propagation: Recently added CNAMEs take time to propagate. See our propagation guide.
Custom domain not working on hosting platform
Most platforms (Netlify, Vercel, Shopify, GitHub Pages) require you to:
- Add a CNAME record pointing your subdomain to their target
- Configure the custom domain in their dashboard
Both steps are required. The CNAME routes traffic to them; the dashboard config tells them to serve your site for that domain.
SSL certificate errors on CNAME'd domain
The hosting provider needs to issue a certificate for your custom domain. Most do this automatically (via Let's Encrypt) once DNS resolves correctly. If you see SSL errors, check that your CAA records allow the provider's CA to issue certificates.
CNAME vs A Record
| CNAME | A Record | |
|---|---|---|
| Points to | Another hostname | An IP address |
| Can be at root domain? | No (unless flattened) | Yes |
| Can coexist with other records? | No | Yes |
| Updates automatically if target IP changes? | Yes | No — you must update manually |
| Best for | Subdomains pointing to third-party services | Root domains, direct IP mappings |
Use CNAME when you want your subdomain to follow a third-party service's IP changes automatically. Use A records when you control the IP and need other record types at the same name.
Recommended Resources
- Free DNS Lookup Tool — Check CNAME and all other DNS records
- DNS Record Types Explained — Complete reference for every record type
- DNS Propagation Guide — Why DNS changes take time
- Free A Record Lookup — Check A records and IPv4 addresses
- Free SSL Certificate Checker — Verify your SSL configuration
Morten Pradsgaard is the founder of exit1.dev — the free uptime monitor for people who actually ship. He writes no-bullshit guides on monitoring, reliability, and building software that doesn't crumble under pressure.