CNAME Checker

What a CNAME record does

A CNAME (Canonical Name) record makes one hostname an alias for another. When a resolver looks up app.customer.com and finds a CNAME to edge.cnames.dev, it restarts resolution at the target and follows it to a final A/AAAArecord. That indirection is what lets a customer point their domain at your platform without ever touching an IP address — and it's why CNAMEs are the backbone of custom domains for SaaS.

Reading the CNAME chain

A lookup can traverse several hops: app.customer.com → xyz.saas.com → edge.provider.net → 203.0.113.10. The checker above follows each hop and shows the full path from two resolvers (Cloudflare and Google). Comparing resolvers catches inconsistent or partially-propagated records — if one shows the new target and the other still shows the old one, the change is mid-propagation.

The CNAME-at-apex problem

You cannot put a CNAME on a root domain (example.com). DNS requires the apex to carrySOA and NS records, and a CNAME is not allowed to coexist with other records at the same name. Attempting it either fails or silently breaks mail and other records. The fixes:

• Use A/AAAA records pointing at the provider's IPs.
• Use a DNS provider that supports ALIAS/ANAME flattening (Cloudflare, Route 53, and others resolve the target and answer with A records at the apex).
• Point www with a CNAME and redirect the apex to it.

Common CNAME errors, and how to fix them

Wrong or stale target

The record exists but points at the wrong host. Enter your expected target in the field above to confirm the final hop matches what your provider told you to use.

Dangling CNAME (takeover risk)

A CNAME pointing at a target you no longer control lets someone else potentially claim it and serve content on your subdomain. Delete CNAMEs for services you've stopped using.

Conflicting records

A CNAME cannot sit alongside other records (like TXT or MX) at the same name. If a verification TXT and a routing CNAME are both needed, put theTXT on a dedicated subname such as _acme-challenge.

Propagation delay

After changing a record, resolvers keep the old value until its TTL expires. Lower the TTL a day before a planned change so the switch is fast, and re-run this checker to confirm both resolvers agree.

CNAMEs and custom domains for SaaS

If you run a SaaS, every customer who wants their own domain sets a CNAME (or apex A records) to your platform — then you have to issue a TLS certificate for it, route it to the right tenant, and keep it renewed. That last part is the hard part, and it's what we do.

Frequently asked questions