How a hostname turns into an address
DNS stores the mapping in two record types. An A record holds a 32-bit IPv4 address such as 203.0.113.10, and an AAAA record holds a 128-bit IPv6 address such as 2001:db8::10 (both are reserved documentation addresses). A name can have any number of each, and it can have neither, for instance a domain used only for email.
The query goes to the public resolvers Cloudflare 1.1.1.1, Google 8.8.8.8 and Quad9 9.9.9.9. The resolver answers from cache or walks the chain from the root servers to the TLD servers to the domain's authoritative nameservers, then returns the final addresses. If the hostname is an alias, the resolver follows the CNAME and you see the addresses of the target, not the alias itself.
Reading the result table
The summary line reports the record count and the lookup time in milliseconds. Each row shows the record type, the address and the TTL. The TTL is the value the resolver reported, so it is the time left in its cache rather than the number configured in the zone. Run the lookup twice and you will often see it count down.
An empty result is a real answer, not a failure: the resolvers returned NODATA or NXDOMAIN for both types, so the name has no address records or does not exist. The tool shows an error only when a query actually failed, for example a SERVFAIL, a timeout, or a name that fails validation such as a reserved or internal hostname.
Copy Records produces one line per record in zone-file order (name, TTL, class, type, value). JSON downloads the whole API response.
Why the address differs from what you see locally
Your laptop asks your ISP's resolver, and that cache may hold an answer that is hours old. The public resolvers used here have their own caches, so the two can disagree during a change. Content delivery networks add another layer: they answer by query location, so a resolver in Frankfurt and one in Singapore legitimately get different IPs.
Round-robin records also arrive in a rotating order. If the same addresses appear in a different sequence next time, nothing has changed. Treat it as a difference only when an address appears or disappears.
- Stale local cache: flush it (ipconfig /flushdns on Windows, resolvectl flush-caches on systemd Linux) and query again.
- GeoDNS or CDN: mixed answers across locations are by design. Compare resolvers with the DNS Change Analyzer.
- Split-horizon DNS: office networks often serve internal addresses for the same name. The answer here is what the rest of the world gets.
Problems this lookup catches and how to fix them
The most common finding after a hosting move is that the name still points at the old server. If the authoritative zone is correct, the stale address is a cache that will expire with the TTL. If the authoritative servers also return the old address, the change was never saved. The DNS Change Analyzer settles that by asking the authoritative nameservers directly.
A missing AAAA record is a warning, not an outage, but a wrong AAAA record is worse than none: dual-stack clients prefer IPv6 and wait for a timeout before falling back. The same applies to an A record left behind after a server was retired. The name resolves, but every connection fails. Confirm each published address answers with Ping.
Apex and www mismatches are easy to spot: look up example.com and www.example.com and compare the rows. If one set is newer than the other, a record was missed during the last change.
What this tool does not tell you
The lookup resolves names. It never connects to the addresses, so it cannot say whether a web server is up or which ports are open. Use Ping for reachability and the Port Scanner for services. It also shows only A and AAAA records: the alias behind a name is in CNAME Lookup, and MX, NS and TXT records are in the full DNS Lookup.
TTLs are available for address records only, which is why this page shows them while the CNAME and TXT tools cannot. Lookups are rate limited per client address and are not stored.