How to Do a Reverse Lookup (PTR)

Normal DNS finds the IP address from a hostname. The reverse, finding the hostname from an IP address, is called a reverse lookup (PTR).

Reverse-look up an IP addressFree, no sign-up

How to look it up

In Web dig, just enter the IP address in the search box. It is automatically converted to the reverse-lookup name (for IPv4, something like 8.8.8.8.in-addr.arpa) and a PTR query is sent.

8.8.8.8.in-addr.arpa.  IN  PTR  dns.google.

Who sets up reverse DNS?

Reverse DNS is managed by whoever holds the IP address (your ISP, or your cloud or server provider). Even someone who can edit a domain’s DNS may not be able to change its reverse DNS. You set it in the provider’s control panel, or request it from them.

Why it matters for mail servers

If a mail-sending server has no reverse DNS, receiving servers may treat its mail as spam. As a rule of thumb, these three should all match.

A reverse lookup of the sending server’s IP address returns a hostname
A lookup of that hostname’s A record returns the original IP address
The name the server announces when sending mail (HELO) also matches that hostname

When no result appears

An IP address with no PTR record set returns no record. The IP addresses of ordinary home connections often have names that the ISP assigned automatically. You can also find out who holds an IP address with Whois.

FAQ

Can a reverse lookup return more than one result?

It can. In general, though, it is recommended to have just one.

Can I do a reverse lookup for IPv6 too?

Yes. If you enter an IPv6 address, it is converted to the ip6.arpa form and queried.

Reverse-look up an IP address

More guides

Last updated: 2026-10-21