01
Keep one item on each line
Blank lines are ignored, but physical line numbers, duplicates and order are preserved. Mix IPv4 reverse DNS and IPv6 reverse DNS inputs in one batch; do not paste a URL, a hostname or a port.
DNS & Domains
Reverse DNS generator
Enter one IP address or CIDR per line. Addresses produce PTR owner names; aligned prefixes produce zone names.
Reverse DNS generator
IP addresses or CIDRs, one per line
Reverse names and address details
Addresses are processed in this browser. No DNS request is sent.
Output options
An undotted name can be relative to a zone-file origin.
IPv6 expands to 32 hex digits. Each digit becomes a reversed label; IPv4 reverses whole octets.
Maximum 100 nonempty lines and 65,536 UTF-16 units. JSON keeps failed rows; names export requires every row to succeed.
Open DNS lookupWaiting to generate the latest input…
Use a reverse DNS generator when a change request needs the exact owner name beneath in-addr.arpa or ip6.arpa. Reversing the written groups of a compressed IPv6 address is not enough: omitted zeros must be restored, then every hexadecimal digit reversed. Compare the expanded address with the name before adding it to a DNS configuration.
Why use this reverse DNS generator
Reverse the right units
The reverse DNS generator treats an IPv4 octet as one label, while IPv6 uses one hexadecimal digit per label. The input stays intact and the expanded form remains beside each result, so an abbreviated address can be reviewed without mental zero counting.
Distinguish a host from a zone
A host produces its complete PTR owner. A CIDR produces one zone for its network prefix, with host bits cleared only in the displayed network. The result marks the two cases separately; a /24 never turns into a list of 256 host records.
Check the prefix before using the name
02
Compare the network with the source
For 192.0.2.129/24, the network is 192.0.2.0/24 and the zone is 2.0.192.in-addr.arpa. The original host bits are not turned into extra labels. Nonaligned prefixes are rejected rather than enlarged.
03
Choose a complete export
Names export is blocked when any row fails. Select JSON to retain the entire report, including errors. Turn automatic generation off for the Generate button or Ctrl/Cmd + Enter; changing an option makes the previous result stale immediately.
Inspect addresses and their DNS labels
A PTR name generator for two address families
IPv4 requires four decimal octets from 0 to 255. IPv6 accepts full or compressed notation, including a dotted IPv4 tail. An IPv4-mapped IPv6 address remains IPv6 and produces an ip6.arpa name, not an in-addr.arpa alias.
One exact reverse zone per aligned prefix
IPv4 prefixes must be multiples of eight and IPv6 prefixes multiples of four. The /0 result is the reverse tree root. A /32 IPv4 or /128 IPv6 input covers one address and is marked as a host.
A report that keeps failed input
Each JSON row contains the original text, source line, address family, kind, expanded address, network, generated name and stable error codes. The first 50 rows appear initially; Show more reveals the remaining rows. Exports include the whole batch.
Generation and delegation have different limits
- No lookup or publication
- A generated name does not establish a PTR record, a reachable hostname, identity or forward/reverse agreement. This page does not query resolvers or publish records. There is no target hostname or TTL field.
- No classless delegation or host enumeration
- Non-octet IPv4 and non-nibble IPv6 prefixes fail on their own line. There is no automatic subnet split, wider covering zone, RFC 2317 CNAME setup, SOA/NS template or enumeration of every host in a CIDR.
- Bare addresses only
- Outer whitespace is trimmed for parsing. IPv4 leading zeros, short or integer forms, interface scope IDs, brackets, ports, ranges, comments and ARPA-to-IP input are rejected. Nothing is silently extracted from a URL.
- A final dot is a formatting choice
- The default trailing dot makes the generated name absolute. Removing it does not change the address, but a zone-file parser may append its current origin to an undotted name. Review the destination format before pasting.
- Bounded batches, no partial names list
- Up to 100 nonempty lines and 65,536 UTF-16 units are accepted. Exceeding either batch limit stops generation. There is no file import, sorting or deduplication. Examples and Clear preview replacement counts; Undo restores the previous input and report.
Reverse DNS generator questions
How is an in-addr.arpa name built?
Reverse the four decimal octets, keep each octet intact and append in-addr.arpa. For 192.0.2.1 the absolute owner is 1.2.0.192.in-addr.arpa. This is the record name; it does not supply the hostname stored in the PTR record.
Why does an IPv6 PTR name contain 32 nibbles?
An IPv6 address has 128 bits. Each hexadecimal digit represents four bits, so the full address has 32 digits. Expand compressed zeros first, reverse those digits individually and append ip6.arpa; reversing only the eight colon-separated groups would be wrong.
Which prefixes can become a reverse zone?
This page accepts IPv4 prefixes /0, /8, /16, /24 and /32, plus IPv6 prefixes divisible by four through /128. It masks host bits for a CIDR. Other prefix lengths can require multiple zones or classless delegation, which this tool deliberately does not generate.
What is RFC 2317 delegation?
RFC 2317 describes classless IPv4 reverse delegation using coordination between parent and child zones, including CNAME records. The necessary names and delegation agreement cannot be inferred from a prefix alone, so this page reports an unsupported boundary instead of inventing that configuration.
Can I set reverse DNS myself?
Only if you control the reverse zone or your address provider gives you a reverse-DNS setting or delegation. Controlling a normal domain does not automatically give control of the IP block. Take the generated owner name to the provider responsible for that address.
Does this tool query DNS?
No. It computes an owner or zone name from the entered address. A successful result can still have no live PTR record. An actual lookup is a separate operation and is not triggered by editing, generating, copying or downloading here.
Have a prefix or address case to check?
Review the name before creating a record
Return to the reverse DNS generator, check the host or zone marker, and export a complete list or a report with the rejected lines.