PTR · in-addr.arpa · ip6.arpa
Reverse DNS lookup
Turn an IPv4 or IPv6 address into its hostname. See the reverse name that was queried, the PTR answer and whether that hostname points back to the same address.
How reverse DNS works
Reverse lookups use special names under arpa. For IPv4 the four numbers are written backwards under in-addr.arpa, so 192.0.2.1 becomes 1.2.0.192.in-addr.arpa. For IPv6 every one of the 32 hexadecimal digits becomes its own label, again in reverse, under ip6.arpa. The tool builds that name, asks for its PTR record and shows the raw answer.
Forward confirmation
A PTR record can claim any name, so the tool also looks up the A or AAAA records of each hostname it finds. If they include the original address, the pair is forward-confirmed (FCrDNS). Mail servers commonly require this from senders, and logs and traceroutes become far easier to read when it holds.
Who controls the PTR record
Reverse zones belong to whoever holds the address block: your ISP, hosting or cloud provider. Your domain’s DNS host cannot set them; ask the provider, or use its control panel if it offers “reverse DNS”.
Frequently asked questions
Why does my IP address have no PTR record?
PTR records are published by whoever holds the address block, usually an ISP or hosting provider. Many home connections and cloud addresses have none, or only a generic name. Only that provider can add one.
What is forward-confirmed reverse DNS?
The address’s PTR name resolves back to the same address. Receiving mail servers often check it, and a missing or mismatched pair can count against the sending server.
Can one address have several PTR records?
DNS allows it, but most software only uses the first answer, so a single PTR record per address is the usual practice.