A DNS lookup asks the domain name system what records a domain publishes: the addresses it points to, the servers that handle its mail, the name servers it is delegated to, and the text records that carry things like SPF. The DNS lookup tool runs the query from your browser, lets you pick the record type, and shows each result with its TTL. You do not need a terminal or any command-line tools.
Here is what each record type tells you, how to read the result, and why the answer you see is not always the live one.
What a lookup actually does
A domain’s records are not held in one place. They live on the domain’s authoritative name servers, and a resolver finds them by following a chain: it asks a root server which servers handle .com, asks those which name servers handle the domain, then asks those for the record you wanted. The resolver caches each step so it does not repeat the whole walk every time.
When you run a lookup, you ask a public resolver to do that walk and hand back the answer. The query leaves your browser over a secure connection; nothing is logged on our side.
Picking a record type
The record type decides what you get back. The common ones:
- A is the IPv4 address a name points to. The first thing to check when a site will not load.
- AAAA is the IPv6 address, for names reachable over IPv6.
- MX lists the mail servers that receive email for the domain, each with a priority. See the MX records guide for how those are ordered.
- NS gives the authoritative name servers the domain is delegated to. These reveal the DNS provider.
- TXT holds free-form text records, used for SPF policies, DKIM keys and ownership-verification tokens.
- CNAME is an alias that makes one hostname stand in for another.
- SOA is the start-of-authority record, with the zone’s primary server, contact and the serial number that changes on every edit.
- CAA says which certificate authorities are allowed to issue certificates for the domain.
The tool defaults to A, since that is the most common check. Change the menu and look up again to switch types.
Reading the result
Each row shows the record’s name, the data, and a TTL in seconds. The data is the value itself: an address for A, a hostname for CNAME, a string for TXT. The TTL is the part people skip, and it matters more than it looks.
The TTL (time to live) is how long a resolver may cache the answer. A TTL of 300 means the value can be served from cache for five minutes before the resolver checks again. So the record you see may be a copy that was cached a few minutes ago, not the value sitting on the authoritative server right now.
That gap explains the most common DNS confusion: you change a record, look it up, and still see the old value. Nothing is broken. The resolver is serving its cache until the TTL runs out. If you know a change is coming, drop the TTL to something small a day ahead, make the change, then raise it again once the new value has settled.
When the answer is empty
If a domain has no record of the type you asked for, the lookup returns nothing for that type and shows the resolver status. NOERROR with no rows means the domain exists but has no record of that type, which is common when you query AAAA for an IPv4-only host. NXDOMAIN means the domain itself does not exist. Reading the status line tells you which case you are in, rather than leaving you guessing.
A lookup needs a connection
Unlike the subnet and conversion calculators on this site, a DNS lookup cannot run offline. It has to ask a name server, so it queries a public resolver over a secure connection each time. The trade-off is that the results are live, give or take the TTL, so you are reading what the domain publishes rather than a stale local copy.
Open the DNS lookup tool, enter a domain, pick the record type, and read the records with their TTLs. For mail-specific checks, the MX lookup breaks out the priorities; for turning an IP back into a hostname, see reverse DNS.