DNS Terminology
This page explains the DNS terms and record types you are most likely to see when using AuthLookup.com to check public DNS records from Cloudflare, Google, Quad9, or authoritative nameservers.
Resolver Terms
- Recursive Resolver
- A DNS resolver that looks up answers on behalf of users and applications. Cloudflare DNS, Google DNS, and Quad9 show recursive views that may be affected by caching and resolver policy.
- Authoritative Nameserver
- A nameserver delegated to answer for a domain. The authoritative option asks the domain's source-of-truth nameservers directly, which is useful when checking whether DNS changes have reached the servers responsible for the zone.
- TTL
- Time to live. TTL is the number of seconds a DNS answer may be cached by resolvers before it should be refreshed.
- DNS Propagation
- An informal term for the period while DNS changes become consistently visible. Records are not pushed to every resolver; authoritative updates and the expiry of previously cached answers determine when different resolver views converge.
- NODATA
- A successful NOERROR response containing no answers of the requested record type. The DNS name may still exist and may have records of other types, so NODATA is different from NXDOMAIN.
- NOERROR, NXDOMAIN, and SERVFAIL
- NOERROR means the DNS query completed successfully, including a possible NODATA result. NXDOMAIN means the name does not exist. SERVFAIL means the resolver or nameserver could not complete the lookup.
- DNSSEC-Validating Resolver
- A recursive resolver that cryptographically checks DNSSEC signatures and the chain of trust. If validation fails, it normally returns SERVFAIL instead of passing the unverified answer to the requester.
Address and Alias Records
- A
- Maps a domain or host to an IPv4 address, such as 192.0.2.10. Use it to check where a website or service points for IPv4 clients.
- AAAA
- Maps a domain or host to an IPv6 address. Use it to confirm whether a service is published for IPv6 clients.
- CNAME
- Creates an alias from one DNS name to another. Use it to see whether a host delegates its final answer to another hostname, such as a CDN or hosted service.
- PTR
- Maps an IP address back to a hostname for reverse DNS. PTR records are commonly checked for mail servers and network diagnostics.
Mail and Text Records
- MX
- Lists the mail exchangers that receive email for a domain, including priority values. Use it to confirm where inbound mail should be delivered.
- TXT
- Stores text values used by many services. TXT records are often used for SPF, domain verification, and other policy or ownership checks.
- CAA
- Controls which certificate authorities are allowed to issue TLS certificates for a domain. Use it to check certificate issuance policy.
Delegation and Zone Records
- Delegation and Glue Records
- A delegation in the parent zone identifies the authoritative nameservers for a child zone. Glue records are supporting A or AAAA addresses supplied by the parent when they are needed to reach an in-zone nameserver without creating a circular lookup.
- NS
- Lists the nameservers delegated for a domain or zone. Use it to confirm which servers are expected to answer authoritatively.
- SOA
- Start of authority. SOA contains zone-level details such as the primary nameserver, responsible mailbox, serial number, and timing values.
Service and DNSSEC Records
- SRV
- Publishes the hostname and port for a named service. SRV is used by some chat, directory, voice, and application protocols.
- DS
- Delegation signer. DS records live in the parent zone and link a delegated domain to its DNSSEC keys.
- DNSKEY
- Publishes the DNSSEC public keys for a signed zone. DNSKEY records are used by validating resolvers to check DNSSEC signatures.
- HTTPS
- A service binding record for HTTPS endpoints. It can advertise connection details such as protocol support and service parameters.
- SVCB
- Service binding. SVCB is a general form of service-binding record that can describe alternative endpoints and connection parameters for supported services.