Reverse DNS lookup
Find the PTR host name behind any IP address — over DNS-over-HTTPS.
Resolved via DNS-over-HTTPS, proxied through our server. Never stored.
How to do a reverse DNS lookup
- Enter an IP. Type an IPv4 or IPv6 address.
- Resolve the PTR. We query the reverse DNS (PTR) record for that address.
- See the host name. View the host name the IP resolves back to, if one is set.
How an IP maps back to a name
Forward DNS turns a name into an address; reverse DNS does the opposite, and it works by a neat trick. The IP
is reversed and placed under a special zone — in-addr.arpa for IPv4, ip6.arpa for
IPv6 — so 8.8.4.4 is queried as 4.4.8.8.in-addr.arpa, and a PTR
record there returns the host name. The crucial detail is who controls it: the PTR zone is delegated
to whoever owns the IP block (the ISP or hosting provider), not to whoever owns the domain. So you can point
mail.example.com at any IP you like, but you can only set that IP's reverse record if your provider
lets you — which is exactly why reverse DNS is a weak signal of identity and a strong signal of network owner.
Why mail servers care (FCrDNS)
Reverse DNS matters most for email deliverability. Receiving mail servers routinely run a forward-confirmed reverse DNS check: they take the sending IP, look up its PTR name, then look that name's forward record back up and confirm it resolves to the same IP. A missing PTR, or one that doesn't round-trip, is treated as a spam signal and can get mail rejected or junked outright. If you run your own mail server, setting a matching PTR (via your hosting provider) is one of the cheapest deliverability wins there is — and this lookup is how you verify it's in place.
What it can and can't tell you
A successful lookup is a fast way to learn which provider an address belongs to — generic PTRs like
pool-72-x-x-x.dyn.example-isp.net reveal the network and often that it's a residential/dynamic
range. But plenty of legitimate IPs have no PTR at all, and a PTR can say anything its block owner chose, so
never treat the name as proof of identity. The query runs through our server and isn't stored. To geolocate the
address, use the IP address lookup;
to go name-to-address, run a forward DNS lookup.
Frequently asked questions
- It finds the host name associated with an IP address by querying its PTR record — the opposite of a normal (forward) DNS lookup that turns a name into an IP.
- PTR records are optional and set by whoever controls the IP block. Many residential and cloud IPs either have none or use a generic provider-assigned name.
- Mail servers check it to reduce spam — a mismatched or missing PTR can hurt deliverability. It also helps identify the network behind an IP during troubleshooting.
- Yes. IPv6 addresses are expanded to their .ip6.arpa form and queried for a PTR record.
- No. The IP is sent to our server, resolved over DNS-over-HTTPS, and the result is returned. Nothing is saved.