Reverse DNS Lookup
PTR records with forward-confirmed checks.
Use the Reverse DNS Lookup tool
What this reverse dns lookup does
Reverse DNS maps an IP address to a hostname through a PTR record in the `in-addr.arpa` or `ip6.arpa` namespace. It is used for logging, diagnostics and mail reputation, where a forward-confirmed reverse DNS name carries more weight.
Forward confirmation means the hostname returned by the PTR record also resolves back to the original IP address. This tool runs both directions and labels each hostname as forward-confirmed or unmatched.
Why use it
- Identify which host or provider owns an IP address.
- Check a mail server's reverse DNS before sending.
- Diagnose why a service rejects connections from an address.
How to use it
- 1Enter an IPv4 or IPv6 address.
- 2Run the lookup.
- 3Compare each hostname with its forward A records and the confirmation label.
Worked examples
Public resolver
Input
1.1.1.1
Output
Hostname one.one.one.one, forward-confirmed by matching A records.
No PTR
Input
A consumer connection with no reverse record
Output
No PTR record; common for residential addresses.
Common mistakes
- Assuming a missing PTR is always a fault; many client connections have none.
- Treating any PTR as trustworthy without checking forward confirmation.
- Entering a hostname instead of an IP address.
Frequently asked questions
Why does my IP have no PTR record?
Reverse DNS is controlled by the network owner, not by you. Many consumer and cloud addresses have none unless the provider configures one.
What is FCrDNS?
Forward-confirmed reverse DNS: the PTR hostname resolves back to the same IP. It is a stronger signal than a PTR alone.
Can I set reverse DNS myself?
Only if you control the IP's reverse zone, usually through your hosting provider. You cannot publish it from your domain's normal DNS panel.