Reverse DNS Lookup
Find the hostname associated with any IP address. Checks PTR records and verifies forward-confirmed reverse DNS.
How to Use the Reverse DNS Lookup Tool
1. Enter any IPv4 or IPv6 address in the input field
2. Click Lookup or press Enter
3. Results show all PTR records (hostnames) associated with that IP
4. Green checkmark means forward-confirmed — the hostname also resolves back to the same IP
5. Yellow warning means the PTR record exists but the hostname does not resolve back to the IP — this may indicate a misconfiguration
Frequently Asked Questions
What is reverse DNS?
Reverse DNS (rDNS) is the process of resolving an IP address back to a hostname. It uses PTR records stored in special DNS zones. For example, the reverse DNS of 8.8.8.8 is dns.google. Regular DNS goes from hostname to IP; reverse DNS goes from IP to hostname.
What is forward-confirmed reverse DNS (FCrDNS)?
FCrDNS means the PTR record (reverse DNS) hostname also has an A record that points back to the original IP address. This two-way verification is important for email servers — mail servers without FCrDNS are often flagged as spam.
Why does my IP have no PTR record?
Many IP addresses have no PTR record configured. This is especially common with residential ISP addresses, cloud instances, and servers where the owner has not set up reverse DNS. It does not indicate a problem unless you are running a mail server.
Why is reverse DNS important for email?
Email servers use reverse DNS to verify that the sending server is who it claims to be. A mail server without a PTR record or with an unconfirmed PTR record is more likely to be rejected by spam filters or have emails delivered to the junk folder.
How do I set up reverse DNS for my server?
Reverse DNS is controlled by whoever owns the IP address block — usually your hosting provider or ISP. You need to contact them and ask them to set a PTR record for your IP pointing to your server's hostname.