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PTR record

Learn what a DNS PTR record is, how it enables reverse lookups (IP to domain name), why it's critical for email deliverability, who manages it, lookup methods, and best practices for forward-confirmed reverse DNS (FCrDNS).

What Is a PTR Record in DNS?

TL;DR
A PTR record (Pointer) maps an IP address back to a domain name — the reverse of A/AAAA records.
It's used for reverse DNS lookups, email server verification, spam prevention, and network troubleshooting.
PTR records live in special reverse zones (in-addr.arpa for IPv4, ip6.arpa for IPv6) and are usually managed by your IP address provider (ISP, hosting company, cloud provider), not your domain registrar.

Look up PTR records
Enter a domain name to lookup PTR records

Enter an IP address for reverse DNS lookup

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How PTR Records Work

  • Forward DNS: mail.example.com → 192.0.2.1 (A record)
  • Reverse DNS: 192.0.2.1 → mail.example.com (PTR record)

When someone performs a reverse lookup on an IP:

  1. The resolver reverses the IP and appends .in-addr.arpa (for IPv4) or .ip6.arpa (for IPv6).
  2. It queries the PTR record in that reverse zone.
  3. It returns the domain name (if set).

Forward-confirmed reverse DNS (FCrDNS): Best practice where forward (A) and reverse (PTR) mapping match exactly.

Common Use Cases

  • Email deliverability: Most mail servers reject or spam emails from IPs without valid PTR records.
  • Spam & abuse prevention: Verifies the sender IP belongs to the claimed domain.
  • Network diagnostics: Identify who owns an IP (e.g., dig -x 8.8.8.8).
  • Security audits: Confirm IP-to-domain mapping.
  • Compliance: Many providers (cloud, hosting) require matching PTR for servers.

How to Lookup PTR Records

dig -x 8.8.8.8
nslookup -type=PTR 8.8.8.8

Record Format

IPv4 (reversed octets + .in-addr.arpa):

1.2.0.192.in-addr.arpa.  PTR  mail.example.com.

IPv6 (reversed nibbles + .ip6.arpa):

1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa. PTR mail.example.com.
  • Managed by whoever owns the IP block (not your domain registrar)
  • Target should match forward DNS for FCrDNS

Valid Examples

Email server (FCrDNS):

# Forward
mail.example.com.     A      192.0.2.1
 
# Reverse (set by IP provider)
1.2.0.192.in-addr.arpa. PTR  mail.example.com.

Google Public DNS:

8.8.8.8.in-addr.arpa.   PTR  dns.google.
8.8.4.4.in-addr.arpa.   PTR  dns.google.

AWS EC2 Example:

1.2.3.4.in-addr.arpa.   PTR  ec2-1-2-3-4.compute-1.amazonaws.com.

PTR vs Forward DNS (A/AAAA)

FeaturePTR (Reverse)A/AAAA (Forward)
DirectionIP → DomainDomain → IP
Zonein-addr.arpa/ip6.arpaYour domain zone
Managed byIP address providerDomain owner/DNS provider
Critical for emailYes (spam checks)Yes (resolution)
Multiple allowedUsually one per IPYes
FCrDNS requirementMust match forwardMust match reverse

→ See also: A Record, AAAA Record

Frequently Asked Questions

Who controls PTR records?
Your IP address provider (ISP, cloud host, hosting company), not your domain registrar or DNS provider.
Why do email servers care about PTR?
They check reverse DNS to verify the sending IP belongs to the claimed domain. Missing/incorrect PTR often leads to spam filtering or rejection.
Can I set my own PTR record?
Only if you control the IP block (rare for individuals). Most people request it from their provider.
What is FCrDNS and why does it matter?
Forward-confirmed reverse DNS: forward lookup (A) and reverse (PTR) match. Many mail servers require it for good deliverability.

References

RFC 1035

Domain Names - Implementation and Specification

Related: A Record · TXT Record (SPF/DKIM/DMARC) · DNS Basics