6 min readcode.live
DNS Lookup: A Debugging Checklist for When 'It Won't Resolve'
A record vs CNAME vs MX, propagation delay, and the order to check things in when a domain isn't resolving the way you expect.
Start with the record type, not the symptom
"DNS is broken" almost always means one specific record type is wrong or hasn't propagated. A record and AAAA handle IPv4/IPv6 resolution, CNAME aliases one hostname to another, MX routes mail, TXT holds arbitrary text (SPF, DKIM, domain verification), and NS delegates a zone to a set of nameservers.
The checklist
When something isn't resolving, work through this order — it catches 90% of real-world DNS issues:
- Query the authoritative nameserver directly, not just your local resolver, to rule out caching
- Check TTL — a low TTL means changes should show up fast, a high one means you're waiting
- Confirm you're editing the zone at the actual registrar/DNS host, not a stale secondary
- CNAME records can't coexist with other records on the same name — a common config error
- MX records need a priority number and must point to a hostname, never a bare IP
Try it on code.live
code.live's DNS Lookup tool queries A, AAAA, CNAME, MX, TXT, and NS records for any domain directly from the server side, so you see exactly what's published without local resolver caching getting in the way.
Key takeaways
- Apply one concrete change from this post before collecting more reading.
- Prefer browser-side tools when the work involves secrets, tokens, or PII.
- Document the why next to the how so the next reviewer inherits context.
FAQ
- Who is this guide on dns for?
- Working developers who need a practical take on dns lookup: a debugging checklist for when 'it won't resolve' — not a marketing overview. Skim the sections, apply one tip, then come back when you hit an edge case.
- Do I need an account to use the related tools?
- No. code.live tools run in your browser with no signup. Nothing you paste is uploaded to a server for the client-side utilities linked from this post.
- How often is this article updated?
- This post was published August 17, 2026. Fundamentals stay stable; check linked tool pages and official docs when version-specific behavior matters.