Reverse DNS Lookup
Find the hostname behind an IP, and check that it points back.
Asked from our server in Newark, US · the root and each reverse zone, the zone’s own name servers, our resolver and our copy of DB-IP
Lookup nameNew
The delegationNew
The round tripNew
StandbyEach PTR name is resolved forward by our resolver. Forward-confirmed means it leads back to the address you entered.
The answer · —
The answer appears here
What to do New
Blocklists New
The delegation and DNSSEC
Every server we asked on the way down, from the root to the reverse zone that holds the record.
The neighbours New
The 8 addresses either side, asked the same question. A shared pattern usually means a pool of customer lines.
The lookup’s path New
Raw answer
Recent lookups
Kept in this browser onlyWhat the reverse DNS lookup does
Normal DNS turns a name into an address. Reverse DNS goes the other way: it asks which hostname, if any, is published for an IP address. The answer lives in a PTR record. The reverse DNS lookup fetches it from our server in Newark, US, then checks whether that hostname points back to the same address.
It also follows the chain of servers that hands out the answer, so you can see who controls the name, and checks what mail servers look at: whether the name looks generic, whether the address is on a blocklist, and how its neighbours are named.
Mail administrators use it most. Many receiving servers check reverse DNS before accepting a message, and a missing or mismatched PTR record is a common reason for mail being rejected or marked as spam. It also helps you put a name to an address in your logs, or confirm that a new server’s PTR record is in place.
How to use the reverse DNS lookup
- Type a public IPv4 or IPv6 address, or use your own.
- Press Look up. Any PTR names are listed, with the servers that hand them out.
- Check Forward-confirmed: whether the name resolves back to the same address. If the address sends email, check the mail list too.
Understanding the results
Each hostname appears with the addresses it resolves to and a forward-confirmed result. Yes means the name leads back to the IP you entered, which is the setup mail servers expect. No means the PTR name exists but doesn’t lead back, so services that check both directions won’t trust it. If no name is listed, the address has no PTR record. If no server answered in time, the result says so; try again shortly.
The lookup name is the special DNS name used for the query. For IPv4, the address is reversed and in-addr.arpa is added, so 8.8.4.4 becomes 4.4.8.8.in-addr.arpa. IPv6 addresses are written out one hexadecimal digit at a time, in reverse, under ip6.arpa.
The delegation shows each server we asked on the way down, from the root to the reverse zone that holds the record. That last zone belongs to whoever controls the address block, and only they can change the name. A name “looks generic” when it contains the address’s own numbers or words such as dsl, pool or dynamic. That’s our rule of thumb; spam filters use similar ones.
Questions
Why is there no hostname?
Publishing a PTR record is optional. Home connections and many cloud servers don’t have a meaningful one.
Why does forward confirmation matter?
Whoever controls an IP block can publish any PTR name. Mail servers trust a name only when it also resolves back to the same IP.
How do I set up a PTR record?
PTR records are set by whoever controls the address block, not in your domain’s own DNS. Hosting companies and cloud platforms usually let you set one in their control panel; on a business connection, ask your internet provider.
Which blocklists do you check?
Six free lists: SpamCop, UCEPROTECT L1, PSBL, Mailspike, DroneBL and S5H. They cover IPv4 only, so IPv6 addresses aren’t checked. To be removed from a list, follow that list’s own instructions.
Who owns the address itself?
A hostname often hints at the provider, but it isn’t proof. We show the network that holds the address and its approximate place (IP location by DB-IP). For the registered owner, use the IP address lookup.
Can I look up private addresses?
No. Private and reserved ranges such as 192.168.x.x have no public reverse DNS, so we refuse them.
Are lookups stored?
Recent lookups stay in your browser. A PDF report keeps a copy so anyone with its reference can verify it.