Reverse DNS Lookup

PTR name: 5.113.0.203.in-addr.arpa

How it works

• Split the address into octets and reversed their order.
• Appended the in-addr.arpa suffix.

• IPv4 reverse zones live under `in-addr.arpa` and IPv6 under `ip6.arpa`, with each nibble as a separate label.
• This tool constructs the name only. To resolve it, query the PTR record with a DNS client; no network request is made here.

Methodology

1. Parse the address as IPv4 (four octets) or IPv6 (eight groups).
2. For IPv4, reverse the octets and append `in-addr.arpa`.
3. For IPv6, expand to eight groups, reverse the 32 nibbles and append `ip6.arpa`.

Usage

1. Enter an IPv4 or IPv6 address.
2. Read the reverse DNS name and the parent zone.
3. Query the PTR record with your DNS tooling.

Examples

These are examples, not current values: they use fixed inputs, while the interactive tool computes live results in your browser.

IPv4 address

{
  "address": "203.0.113.5"
}

IPv6 address

{
  "address": "2001:db8:1234:5678:9abc:def0:1234:5678"
}

Private IPv4

{
  "address": "192.168.0.1"
}

Limitations

Why reverse DNS exists

The forward DNS tree is keyed by name; reverse DNS is keyed by address. To make that fit, the address is reversed and placed under a special top-level zone: `in-addr.arpa` for IPv4 and `ip6.arpa` for IPv6.

A PTR record at that name maps the address back to a hostname. It is used for logging, mail reputation and troubleshooting, and it is controlled by whoever owns the address block.