Reverse DNS (PTR)
Find the hostname(s) associated with an IP address.
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Enter a ip address above and press Run to start the check.
About the Reverse DNS (PTR)
Reverse DNS performs a PTR (pointer) lookup to find the hostname or hostnames associated with an IP address. It works by querying the in-addr.arpa zone for IPv4 or ip6.arpa for IPv6, which the address block's owner controls. Reverse DNS is widely used by mail servers to verify senders, so a correct PTR record is essential for email deliverability and for identifying which host is behind an address.
How to use
- Enter the IPv4 or IPv6 address you want to look up.
- Run the query to retrieve the PTR record from the reverse zone.
- Review the returned hostname and confirm it matches the expected forward record.
Why a reverse lookup often returns nothing — and who controls it
Reverse DNS is not the inverse of a forward lookup, and it is not maintained by the same people. A PTR record lives in a completely separate zone — `in-addr.arpa` for IPv4, `ip6.arpa` for IPv6 — delegated by the regional registry to whoever holds the IP block. That is your hosting provider or ISP, not your domain registrar. This is why setting an A record does nothing for the reverse, and why an empty PTR usually means opening a ticket rather than editing your own zone.
The asymmetry runs deeper: forward and reverse need not agree, and many IPs have no PTR at all. On a residential connection you will typically see a generated hostname from the ISP's own domain, which tells you the network operator and nothing about who is using the address. Cloud providers usually assign a similar placeholder until you request otherwise.
The one place it genuinely matters is outbound mail. Many receiving servers check that a sending IP has a PTR, and that the hostname it returns resolves forward back to the same IP — a matching pair known as forward-confirmed reverse DNS. A missing or mismatched PTR is a common, quiet reason legitimate mail from a new server lands in spam, and it is invisible from the sending side unless you look for it.
Frequently asked questions
- What is a PTR record?
- A PTR record maps an IP address back to a hostname, the reverse of an A or AAAA record. It lives in the in-addr.arpa or ip6.arpa reverse DNS zone.
- Why does my IP have no reverse DNS?
- Reverse DNS is configured by whoever controls the IP block, usually your hosting provider or ISP. If no PTR record is set, the lookup returns nothing.
- Does reverse DNS affect email?
- Yes. Many receiving mail servers check that a sending IP has a valid PTR record, and often that it matches the forward DNS, before accepting mail.