Reverse DNS PTR Record Generator

How to use

1. 1Enter an IPv4 or IPv6 address, or a CIDR block like 203.0.113.0/24 or 2001:db8::/48. The examples cover single addresses and blocks for both versions.
2. 2Type the hostname each address should point to and a TTL in seconds. For a block, the generated PTR targets are placeholders you edit to your real host names.
3. 3For a single address, copy the reverse query name, the PTR resource record, or the dig command shown to verify it once published.
4. 4For a CIDR block, review the reverse zone to delegate, the list of reverse names, and the BIND zone file with owner names relative to the zone.
5. 5Copy the zone file or individual records and paste them into your DNS provider or name server. Reverse DNS is published by whoever controls the IP block, often your hosting provider.

About this tool

Reverse DNS PTR Record Generator builds the names and records that make an IP address resolve back to a hostname. A forward DNS lookup turns a name like mail.example.com into an IP; reverse DNS does the opposite, mapping an IP back to a name through a PTR record published under the special in-addr.arpa tree for IPv4 or the ip6.arpa tree for IPv6. Reverse DNS matters most for outbound mail: a large share of receiving mail servers reject, throttle, or down-score messages from a sending IP that has no matching reverse DNS, so setting up a correct PTR record is part of getting email delivered. It also makes server logs, traceroute output, and access lists readable, and many SSH and monitoring setups expect it. The mechanical part is fiddly to do by hand, which is exactly what this tool removes. For IPv4 it reverses the four octets and appends in-addr.arpa, so 192.0.2.25 becomes 25.2.0.192.in-addr.arpa. For IPv6 it expands the address to all 32 hexadecimal nibbles, reverses them one nibble per label, and appends ip6.arpa, so 2001:db8::1 becomes a 32-label name that is almost impossible to type correctly by hand. Enter a single address to get its reverse query name, a ready PTR resource record line with your chosen target hostname and TTL, and a dig command to verify it. Enter a CIDR block such as 203.0.113.0/24, 198.51.100.8/29, or 2001:db8:abcd:12::/64 and the tool masks the address to its network base, works out the reverse zone you delegate, and lists every PTR record in the range, capped so the page stays responsive on large blocks. It also assembles a complete BIND reverse zone file with the correct $ORIGIN, a TTL, and owner names written relative to the zone, ready to paste into a name server or hand to whoever runs your reverse DNS. Everything is computed in your browser with plain string and BigInt math. The tool never sends a DNS query, never contacts a name server, and works offline once the page has loaded, so the addresses you enter stay on your device. It is a generator, not a resolver: it shows you the records to publish, it does not look up what is currently published. Useful for sysadmins and SREs configuring reverse DNS for a new mail server, hosting customers delegating a block their provider assigned, network engineers documenting a subnet, and anyone who needs the arpa name for an IPv6 address without counting nibbles by hand.

Free to use. Works in your browser. No signup, no login.