Reverse DNS (rDNS) Lookup
Query the hostname associated with an IP address via PTR records.
What is Reverse DNS?
Reverse DNS queries PTR records to find the hostname for an IP address — the opposite of normal DNS resolution.
Forward Confirmation
Checks whether the hostname in the PTR record actually resolves back to the original IP address.
Use Cases
Commonly used for email server verification, network troubleshooting, and security analysis.
What is reverse DNS (rDNS)?
Reverse DNS is the opposite of a normal DNS lookup: it finds the hostname linked to an IP address. This information is kept in a PTR record set by the owner of the IP block; for example, the PTR record of 8.8.8.8 is dns.google.
The tool looks up the PTR record of IPv4 and IPv6 addresses and checks whether the hostname it finds resolves back to the same IP address. This two-way check is called FCrDNS (forward-confirmed reverse DNS) and matters especially for mail servers.
How to use
- 1Enter an IPv4 or IPv6 address.
- 2Press Query.
- 3Review the PTR record and the forward confirmation result.
Frequently asked questions
Why does a PTR record matter for email?
Email providers such as Gmail and Outlook check whether the IP address of the connecting server has a PTR record and whether it resolves back to the same address. Email from servers without a PTR record, or with one that looks like a home connection, may be rejected or go to spam.
How do I change a PTR record?
A PTR record is managed by the owner of the IP address, not in your domain's DNS panel. If your server is with a hosting or data center company, change it through their panel or support team; if you own the IP block, you manage the reverse DNS zone on your own DNS servers.
What does a failed forward confirmation (FCrDNS) mean?
It means the hostname in the PTR record does not resolve to the same IP address. You can fix it by adding an A record (AAAA for IPv6) for the hostname that points to the IP address.
Can an IP address have more than one PTR record?
It is technically possible but not recommended, as many systems only look at the first record. For mail servers, it is best for each IP address to have a single PTR record that matches the name the server announces in SMTP (HELO).