Introduction

A CNAME record not resolving usually means the alias chain is broken somewhere between the hostname you control and the final target it depends on. The visible symptom looks simple, but the real problem may be a conflicting record, an invalid target, a broken downstream zone, or a provider rule about where CNAMEs are allowed.

Symptoms

  • A subdomain with a CNAME does not load, while other hostnames still work
  • DNS lookups return no answer, the wrong answer, or an incomplete chain
  • The issue started after moving providers, changing target services, or editing the zone
  • External DNS checkers disagree depending on the resolver used
  • The apex domain works, but the aliased subdomain fails

Common Causes

  • The CNAME points to a target that no longer resolves
  • Another record type conflicts with the CNAME on the same hostname
  • The DNS provider flattens or proxies records in a way that changes the expected answer
  • Delegation or nameserver changes broke the target zone or alias chain
  • TTL and caching differences hide the new target behind stale answers

Step-by-Step Fix

  1. Query the failing hostname and follow the full CNAME chain until you see where resolution stops or changes unexpectedly.
  2. Confirm that the target hostname itself resolves correctly and still points to the live platform you expect.
  3. Check for conflicting A, AAAA, TXT, or other records on the same name, because a hostname cannot safely act as both a CNAME and another record type.
  4. Review DNS provider behavior such as flattening, proxy mode, or synthetic answers that may alter how the alias is returned.
  5. Verify that both the alias zone and the target zone have correct delegation and active authoritative nameservers.
  6. Compare authoritative answers with public recursive resolver results to distinguish stale cache from broken zone data.
  7. Correct the CNAME target or remove the record conflict, then wait only for the relevant TTLs to expire.
  8. Retest from multiple external resolvers so you know the alias chain is stable across the public internet.
  9. Keep dependent target ownership documented so future platform changes do not leave aliases pointing at dead services.