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Reverse DNS / PTR Converter

Build IPv4 host reverse names and IPv6 host or nibble-aligned reverse-zone names.

Local calculation · inputs are not sent to a server.

Result

Calculating the example…

How it works

IPv4 reverses its four decimal octets under in-addr.arpa. IPv6 expands the address to 32 hex digits, reverses individual digits and appends ip6.arpa. A reverse zone keeps only the network prefix digits before reversal.

Worked example

10.42.7.93 becomes 93.7.42.10.in-addr.arpa. For 2001:db8:42::/48, the zone is 2.4.0.0.8.b.d.0.1.0.0.2.ip6.arpa.

Inputs, edge cases & common mistakes

This creates owner names, not live DNS records or lookups. IPv6 zone prefixes must be multiples of four; other boundaries require multiple zones or a delegation strategy. IPv4 CIDR input is rejected because classless reverse delegation requires additional design (RFC 2317).

Technical references

Reviewed 9 September 2026. Found an issue? Send a correction with a reproducible example.