DNS

PTR Lookup

PTR Records

Resolve an IP back to its hostname

Accepts IPv4 or IPv6. We'll query the matching .arpa zone and forward-confirm the result.
No IP resolved yet

Enter an IP address above to see its reverse DNS hostname, whether it forward-confirms, and who owns the address block.

Tool features

Comprehensive reverse DNS analysis with provider detection and hostname validation
4 checks

Reverse DNS Lookup

Convert IP addresses back to hostnames using PTR records

Provider Detection

Identify ISPs, cloud providers, and hosting services

Hostname Validation

Validate hostname format and detect potential issues

Fast Analysis

Quick categorization and analysis of reverse DNS records

What is reverse DNS & how it works

How an IP address maps back to a hostname

Reverse DNS (rDNS) is the mirror image of a normal lookup: instead of turning a hostname into an IP, it turns an IP address back into a hostname. It's driven by PTR records published in a special reverse zone, and it's what lets a server prove which name an address is meant to represent.

rDNS matters most for email deliverability — receiving mail servers check that a sending IP has a valid PTR record that resolves back to it (forward-confirmed rDNS). This lookup resolves the PTR for an IPv4 or IPv6 address, identifies the network provider, and validates the hostname.

PTR record
The reverse record mapping an IP address back to a hostname.
Reverse zone
The in-addr.arpa / ip6.arpa zone where PTR records live, set by the IP owner.
FCrDNS
Forward-confirmed rDNS — the PTR host resolves back to the same IP.

How to use this tool

Run a reverse DNS lookup in four steps
1
Enter an IP address
Type an IPv4 or IPv6 address, e.g. 8.8.8.8, or click “Use My IP”.
2
Run the lookup
Click Lookup Hostname to query the PTR record in the reverse DNS zone.
3
Review the hostname
See the resolved hostname, the detected provider, and hostname validation.
4
Confirm the mapping
For mail servers, verify the PTR host also resolves forward to the same IP (FCrDNS).

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Frequently asked questions

Common questions about reverse DNS
5 Q&A

Reverse DNS (rDNS) resolves an IP address back to a hostname using a PTR record, the opposite of a normal forward lookup that turns a hostname into an IP.

A PTR (pointer) record maps an IP address to a hostname. It lives in a special reverse zone (in-addr.arpa for IPv4, ip6.arpa for IPv6) and is controlled by whoever owns the IP block — usually your ISP or hosting provider.

Many mail servers reject or flag messages from IPs that lack a valid PTR record, or whose PTR doesn’t forward-resolve back to the same IP. Correct rDNS (FCrDNS) is important for reliable email deliverability.

The owner of the IP address block does — typically your ISP, hosting provider or cloud platform. To set or change a PTR record you usually request it through their control panel or support, not your own DNS zone.

Not every IP has a PTR record — the block owner may not have configured one. Residential and dynamic IPs often have generic or missing rDNS, which is one reason they’re discouraged for sending mail.