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Reverse DNS

Lookup domain name from an IP address.

Examples: 8.8.8.8|1.1.1.1|2001:4860:4860::8888

What is reverse DNS?

Normal DNS turns a name into an IP address. Reverse DNS does the opposite: it asks which host name is linked to an IP address. The answer is stored in a PTR record, which is published by whoever controls the address.

Reverse DNS is useful to identify a server in your logs, to troubleshoot email delivery, and to get a quick hint about who runs an address.

How it works

Behind the scenes, the lookup follows three steps.

Step	What happens
1. Reverse the address	The IP address is written backwards. For example, 192.0.2.10 becomes 10.2.0.192.
2. Add a special suffix	IPv4 addresses use in-addr.arpa and IPv6 addresses use ip6.arpa, so the example becomes 10.2.0.192.in-addr.arpa.
3. Ask for the PTR record	The resulting name is queried and the host name stored there is returned.

Good to know

Points that help you interpret the answer.

Many addresses have none. A missing PTR record is normal and does not mean something is broken.
More than one name. An address can have several PTR records.
Not proof of ownership. The owner of the address can set any name, so treat the result as a hint.
Email servers. Many mail servers check that the sending IP has a matching reverse record.