PTR (Reverse DNS) Lookup
Look up PTR records (reverse DNS) for any IP via in-addr.arpa across 12 global resolvers. Free real-time checker.
What is a PTR record?
A PTR record maps an IP address back to a hostname — the reverse of an A/AAAA lookup. It lives under the in-addr.arpa (IPv4) or ip6.arpa (IPv6) zones. Reverse DNS is configured by whoever controls the IP, not the domain owner — typically a hosting provider, ISP, or cloud platform.
When to check PTR records
- Setting up an outbound mail server — many receiving servers reject mail from IPs without proper reverse DNS
- Spam-blocklist debugging — mismatched forward/reverse DNS is a red flag
- Auditing logs to identify the owner of a connecting IP
FAQ
How do I look up a PTR record?
Enter the reverse-arpa form of the IP. For example, IPv4 8.8.8.8 is 8.8.8.8.in-addr.arpa. WhereIsDNS accepts this form directly when you select PTR.
Why do mail servers care about reverse DNS?
Receiving mail servers commonly require that the connecting IP have a PTR record, and that the PTR's hostname forward-resolves back to the same IP ("forward-confirmed reverse DNS," FCrDNS). It's a low-effort spam filter.
All record-type lookups
WhereIsDNS has dedicated pages for each common DNS record type. Each one defaults the tool to that record type and includes background on what the record means and what to look for.
- A Record Lookup — IPv4 addresses for a hostname
- AAAA Record Lookup — IPv6 addresses for a hostname
- CNAME Lookup — Aliases pointing one hostname to another
- MX Record Lookup — Mail servers for a domain (with priorities)
- NS Record Lookup — Authoritative nameservers for a domain
- TXT Record Lookup — SPF, DKIM, DMARC, and other text records
- SOA Record Lookup — Authority metadata for a DNS zone
- CAA Record Lookup — Which CAs may issue certs for the domain
- Home (defaults to A records)