PTR record (reverse DNS)

What a PTR record is

Ordinary DNS answers the question "which address belongs to this name?" A PTR record answers the reverse: "which name belongs to this address?" PTR records live in special zones. For IPv4, the address is reversed and placed under in-addr.arpa, so the PTR for 203.0.113.7 is stored at 7.113.0.203.in-addr.arpa. For IPv6, each hex digit is reversed individually under ip6.arpa.

The owner of the address block, not the owner of the domain, controls the PTR record. That is why a home connection usually has a generic name assigned by the ISP, such as dynamic-203-0-113-7.example-isp.net, and why you cannot set one yourself unless your provider delegates it to you.

Why it matters

Mail servers are the heaviest users of PTR records. Most of them refuse or heavily penalize mail from an address with no PTR record, or with a PTR that does not resolve back to the same address (a "forward-confirmed" check). A matching PTR is one of the basic requirements for deliverability alongside SPF, DKIM, and a clean blocklist record.

For proxy and VPN users the PTR is a quiet giveaway. A hostname containing words like vps, cloud, static, or a hosting company's domain tells any site that the address is a server, even before an ASN lookup confirms it. Consumer connections, by contrast, usually show the ISP's own domain and a pattern that looks like a dynamic pool.

How to check

The reverse DNS tool returns the PTR record for any address and verifies whether the name resolves forward to the same address. IP lookup shows the hostname next to the address, and the DNS lookup tool can query PTR records directly if you prefer to see the raw answer.

Common misconceptions

A missing PTR does not mean an address is suspicious; many residential ranges have none at all. And a PTR record is not proof of anything, since the block owner can publish any name they like. Treat it as one hint among several.