About the IP to Hostname
Reverse DNS maps an address back to a name through a PTR record in the in-addr.arpa (IPv4) or ip6.arpa (IPv6) tree. The owner of the address block sets it, which is why a home connection usually shows an ISP-generated name and a mail server shows the name its operator chose. Mail servers care about it a lot: many receivers reject or score down mail from an address whose PTR record is missing or does not match the sending hostname.
This page builds the reverse name for each address you enter, IPv6 included, queries the PTR record through our edge function and lists the answer next to the address. An empty answer with NXDOMAIN means the block owner has not published a reverse record, which is common for cloud addresses until you set one.
Only the addresses are sent and nothing is stored. For the forward direction use Hostname to IP; to find who owns the address block use the WHOIS lookup.
How to use
- Paste IPv4 or IPv6 addresses, one per line, up to 20.
- Press Look up; each address shows its PTR hostname or the reason it has none.
- For mail servers, compare the hostname with the name the server uses in its greeting.
Common questions
- Who sets the PTR record?
- The organisation that controls the address block, usually the ISP or cloud provider. Cloud consoles let you set it for addresses you rent.
- Why does the reverse name differ from the website name?
- One address often hosts many names, and PTR can hold only one. Shared hosting and CDNs return a generic name or none at all.
- Does it work with IPv6?
- Yes. The address is expanded to 32 nibbles and reversed into ip6.arpa before the query.