A DNS tool opens with A, AAAA, CNAME, MX, TXT and NS. It looks intimidating, but the basic question is simple: what has this domain registered in the Internet's directory?
Why a browser needs DNS
People remember example.com; network connections use IP addresses. A browser normally asks the operating system or a recursive resolver. The resolver checks its cache and, when needed, follows the DNS hierarchy to an authoritative server.
A and AAAA
An A record returns IPv4. AAAA returns IPv6. The address is not necessarily the origin server: a proxied or CDN-backed site commonly exposes an edge address instead.
For partial IPv6 failures, use the DNS-first IPv6 checklist.
CNAME is an alias, not a redirect
A CNAME says that one name is an alias of another. It does not rewrite the browser address bar. HTTP 301 and 302 responses perform web redirects; DNS only helps resolve the name.
MX, TXT and NS
MX records tell senders where mail for a domain should go. TXT records carry ownership checks and mail policies such as SPF, DKIM and DMARC. NS records identify the authoritative DNS servers for a zone.
Why two people can receive different answers
Resolvers cache answers for the record's TTL. A recent change can be visible through one resolver while another still holds the previous value. CDNs, internal networks, IPv4/IPv6 differences and negative caching can also change what is returned.
What a lookup cannot prove
A correct DNS answer does not prove that routing, TLS or HTTP is healthy, and it does not reveal an origin hidden behind a proxy. Check resolution, connection, certificate and HTTP response as separate layers.
When the fault is in publishing rather than resolution, follow the Cloudflare Pages and GitHub workflow.
- A: IPv4
- AAAA: IPv6
- CNAME: name alias
- MX: mail exchanger
- TXT: text and verification
- NS: authoritative name servers