Reverse DNS Lookup

Reverse DNS maps an IP address back to a hostname using a PTR record. Network operators use it to label servers and routers, and email providers use it to judge whether a mail server is legitimate.

Tool status: Fully functional Runs entirely on this website or in your browser.

What this tool can and cannot do

Only the owner of an IP block can create its PTR records, so many addresses have none.

Data sources: Public DNS-over-HTTPS resolvers

Understanding the results

Forward-confirmed reverse DNS (FCrDNS) means the PTR hostname resolves back to the same IP. This is a basic requirement for running a reputable mail server.

Troubleshooting

Need a PTR record for your server? Request it from your hosting provider or ISP; you cannot set it in your own domain's DNS.

Frequently asked questions

What is in-addr.arpa?

It is the special DNS zone used for IPv4 reverse lookups. The IP is written backwards, e.g. 1.2.0.192.in-addr.arpa for 192.0.2.1. IPv6 uses ip6.arpa.