rDNS (PTR record)
rDNS is a reverse DNS lookup: it finds the host name linked to an IP address from its PTR record.
Updated · Prokso editorial team
Regular DNS turns a site name into an address. Reverse DNS works the other way round: for an address it returns the name that the network owner wrote in the PTR record.
Such a name often reveals the network type. Home subscribers have names like "dynamic" or "pool" with the ISP's name, while servers have hosting names or an empty record.
Websites and mail servers use rDNS as one of the signs of who is contacting them. Together with the ASN, it helps tell a home address from a server address.
Only the network owner can change a PTR record, so for residential and mobile addresses it is the one set by the ISP or carrier.
How to read a name from a PTR record
ISPs build names from a template, and it often contains the address itself and a hint about the connection type. The name cpe-203-0-113-5.dynamic.example-isp.net almost certainly belongs to a home subscriber, while vps-203-0-113-5.example-host.com belongs to a rented server.
| Name fragment | What it usually means |
|---|---|
dyn, dynamic, pool, dsl, cable | a home subscriber with a dynamic address |
mobile, lte, a carrier name | a mobile network |
static, vps, server, cloud | a server or a static address |
Forward check: does the name confirm the address
Anyone who owns a block of addresses can write any PTR record. That is why mail servers and some websites run a double check: they find the name by the address and then the address by that name. If it matches the original one, the name is considered confirmed.
You can repeat this in a terminal: dig -x 203.0.113.5 +short returns the name, and dig +short with that name should return the same address. A mismatch does not mean anything bad by itself, but it lowers trust in the name. For proxies, checking one or two addresses from a set is usually enough to see the naming pattern of the whole network.
What to do about it when working through a proxy
You cannot change a proxy's PTR record, so reverse DNS is taken into account when you choose the address type. If the task needs a network that looks like a home one, and server addresses carry vps or cloud in their names, use residential proxies.
Do not overrate this signal. Many home addresses have no record at all, and websites look at the name together with the network number, not on its own. Read about network numbers in the ASN article.
FAQ
How do I find an address's rDNS?
In a terminal, with the nslookup or dig -x command followed by the address. Many IP lookup services also show the host name.
Does every address have a PTR record?
No. Some networks do not fill in the record, and then a reverse lookup returns nothing.
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