Reverse DNS Lookup (PTR Record)
Resolve IPv4 and IPv6 addresses to their hostnames using client-side DNS-over-HTTPS (DoH).
Examples
Google Public DNS PTR
IP: 8.8.8.88.8.8.8.in-addr.arpa PTR dns.google.Resolves Google's 8.8.8.8 IPv4 address back to dns.google.
About this tool
A reverse DNS lookup maps an IP address back to a hostname through PTR records. IPv4 queries live under in-addr.arpa with the octets reversed — 8.8.8.8 becomes 8.8.8.8.in-addr.arpa — while IPv6 uses ip6.arpa with every hex digit reversed. The tool builds the right query name for either family and sends the PTR query over DNS-over-HTTPS to Cloudflare, Google or Quad9.
Reverse DNS matters most for email. Receiving servers compare the connecting IP's PTR with the name the client presents — forward-confirmed reverse DNS (FCrDNS): the PTR hostname must itself resolve back to the same IP. A missing or mismatched record is a classic spam signal, so messages bounce or get junk-foldered.
You cannot publish a PTR record in your own domain's zone — the reverse tree is delegated to whoever controls the IP block, usually your host or ISP, so changes go through them. On the command line, dig -x <address> runs the same query.
How to use this tool
Enter an IP address
Type an IPv4 address like 8.8.8.8 or an IPv6 like 2001:4860:4860::8888.
Choose a resolver
Pick Cloudflare, Google or Quad9 as the endpoint answering the PTR query.
Run the lookup
Press lookup or Enter; the address is converted to arpa form and PTR records fetched.
Read the result
The matching hostname — or a clear no-records answer — is shown; copy it for your notes.
Use cases
Email deliverability audit
Verify that your mail server IP address has a matching valid reverse DNS (PTR) record to prevent spam filtering.
Server log analysis
Identify hostnames behind IP addresses appearing in server access or security firewall logs.
Common mistakes
Mistake:Assuming every IP has a PTR record.
Fix:PTR records are optional and configured by the IP owner or hosting provider. Residential or unconfigured server IPs will return No Records Found.
Frequently asked questions
Who can set the PTR record for my IP?
The owner of the IP block — normally your host or ISP. The reverse tree under in-addr.arpa and ip6.arpa is delegated alongside the address blocks, so PTR changes go through the provider's panel or a support ticket, not your own DNS.
Why do mail servers reject IPs without reverse DNS?
Legitimate senders almost always have correctly configured rDNS, so a missing or mismatched PTR is a strong spam indicator. Many receivers run the FCrDNS check before accepting mail, so messages from unconfigured addresses can bounce even with valid SPF and DKIM.
What is forward-confirmed reverse DNS?
A two-direction consistency check: the IP's PTR record yields a hostname, and that hostname's A or AAAA record must resolve back to the original IP. When both lookups agree, the address is forward-confirmed — evidence the sender is associated with the domain it claims.
Does it work for IPv6?
Yes. IPv6 lookups use the ip6.arpa zone, where the expanded 32-hex-digit address is reversed one nibble per label. Enter the address in compressed form and the tool expands and reverses it before querying.
Related guides
IP Intelligence — PTR, ASN, and RBL in One Lookup
Reverse DNS, Team Cymru ASN mapping, and Spamhaus ZEN status for public IPs via the DevTools backend. Use it when you need reputation context, not just a PTR.
What Is Reverse DNS (PTR) and How Does It Work?
Understand PTR records, reverse DNS zones, and common uses for IPv4 and IPv6 address lookups. Use them for mail, logs, and host identification.
References & standards
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