DNS Lookup
Look up a domain's DNS records — A, AAAA, CNAME, MX, NS, TXT, SOA and CAA.
What DNS is
DNS (Domain Name System) is the internet's "phone book": it translates names people can remember (example.com) into the numeric addresses machines actually use. Every domain publishes a set of records, and each record type answers a different question — which server delivers the pages, which one receives the email, who is authoritative for the zone. This tool asks those questions of public resolvers (Cloudflare and Google) from the Nexinon server — the browser alone has no access to the DNS protocol.
The record types
A and AAAA point the domain at an IP address (IPv4 and IPv6, respectively). CNAME says a name is an alias of another (common for www and service subdomains). MX lists the servers that receive the domain's email, each with a priority number — lower number, higher preference. NS indicates which name servers are authoritative for the zone. TXT holds free-form text used for verifications — SPF, DKIM and DMARC (email anti-spam/anti-fraud) and service ownership proofs live here. SOA carries the zone's administrative metadata (primary server, contact, serial numbers and timers). CAA declares which certificate authorities may issue TLS certificates for the domain.
TTL and propagation
Every answer carries a TTL (time to live): how long that value may be cached before being asked again. That is what explains "propagation" after a DNS change — there is no synchronized wave updating the internet; each resolver simply keeps the old value until its TTL expires. That's why a recent change can show up here before (or after) it shows up on your network: the TTL displayed is what remains of the queried resolver's cache, not necessarily the value configured in the zone.
Frequently asked questions
Different resolvers can hold caches from different moments — this tool asks Cloudflare's and Google's public resolvers from the Nexinon server, while your terminal usually asks your network's resolver. Right after a DNS change it's normal for each one to answer a different version until the TTLs expire. Some providers also vary the answer by region (GeoDNS) — in that case, the answer depends on where the question comes from.
It's the priority: when there is more than one mail server, senders try the lowest number first; the others are backups (or share the load, when the number is the same). "10 mail.example.com." means mail.example.com has priority 10.
Because they are distinct names in DNS — every subdomain has its own records. Very often www is just a CNAME pointing at the root domain, but nothing requires that: query exactly the name you want to inspect.
DNS distinguishes two kinds of absence: the whole domain not existing (NXDOMAIN — the tool reports "domain not found") and the domain existing without records of the type asked (e.g.: a domain with no email has no MX). The distinction comes from the protocol itself, and hiding it would mask a useful diagnosis.
It's the absolute form (FQDN) used by the protocol itself — the trailing dot marks the root of the DNS hierarchy, and answers are shown as they arrive, untouched. Tools like dig display them the same way.
Not yet — reverse lookup (PTR records) is a different query, made on the IP instead of the domain, and is planned as its own IP inspection tool. Here, IP addresses are not accepted as input.