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Reverse DNS Lookup

A reverse DNS lookup reads the PTR name for an IPv4 or IPv6 address and checks whether that name points back at the same address.

This check runs on our server. The address you enter is used only for this check and is not stored.
Updated

This check runs on our server. The address you enter is used only for this check and is not stored.

How to use the Reverse DNS Lookup

  1. Enter a public IPv4 or IPv6 address.
  2. Pick a resolver.
  3. Tick the robot check and press Look up.
  4. The name is the PTR. "Confirms the IP" is yes when that name resolves back to the address you entered.

How it works

This check runs on our server. The address is not stored.

IPv4 8.8.8.8 is queried as 8.8.8.8.in-addr.arpa. IPv6 is reversed nibble by nibble under ip6.arpa. The PTR answer is a hostname. The tool then queries A and AAAA for that hostname. If one of those addresses is the one you typed, the row is marked as a match. Mail servers often require this round trip before they accept mail from an IP.

Private and loopback addresses are refused. There is no public reverse zone for them that this site should query on your behalf.

Examples

  • Reverse DNS of 8.8.8.8 is dns.google, and that name resolves back to 8.8.8.8.
  • Reverse DNS of 1.1.1.1 is one.one.one.one, and that name resolves back to 1.1.1.1.
  • An address with no PTR returns "This address has no PTR record."

Limitations

  • You cannot edit the PTR here. The address owner sets it with their network provider.
  • A name can have several addresses. The match is yes when your IP is one of them.
  • IPv6 reverse names are long. The page shows the hostname from the PTR, not the nibble form, once the answer arrives.

Frequently asked questions

What is a PTR record?

It maps an IP address back to a hostname. Forward DNS maps the hostname to the address. Both directions are published separately, so they can disagree.

Why does the forward check fail?

The PTR name exists, but its A or AAAA records do not include the address you looked up. Mail and some login checks treat that as a mismatch.

Can I look up 192.168.0.1?

No. Private, loopback, and link-local addresses are refused.

Often used together with the Reverse DNS Lookup.

  • DNS Lookup

    One table of A, AAAA, MX, NS, TXT, SOA, and CAA records for a domain.