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.
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:
- The resolver reverses the IP and appends
.in-addr.arpa(for IPv4) or.ip6.arpa(for IPv6). - It queries the PTR record in that reverse zone.
- It returns the domain name (if set).
Forward-confirmed reverse DNS (FCrDNS): Best practice where forward (A) and reverse (PTR) mapping match exactly. For the full validation flow, see how to check reverse DNS and FCrDNS.
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 8.8.8.8nslookup -type=PTR 8.8.8.8Record 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)
| Feature | PTR (Reverse) | A/AAAA (Forward) |
|---|---|---|
| Direction | IP → Domain | Domain → IP |
| Zone | in-addr.arpa/ip6.arpa | Your domain zone |
| Managed by | IP address provider | Domain owner/DNS provider |
| Critical for email | Yes (spam checks) | Yes (resolution) |
| Multiple allowed | Usually one per IP | Yes |
| FCrDNS requirement | Must match forward | Must 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
Related: Reverse DNS Lookup Guide · A Record · TXT Record (SPF/DKIM/DMARC) · DNS Basics