Reverse DNS Lookup Tool
Find domain names associated with an IP address. Discover which domains are hosted on a specific IP.
Enter an IP address to perform a reverse DNS lookup.
What is a Reverse DNS Lookup?
A reverse DNS lookup is the opposite of a regular DNS lookup. Instead of finding the IP address associated with a domain name, a reverse DNS lookup finds the domain name(s) associated with an IP address.
Technically, reverse DNS uses PTR (Pointer) records in a special domain called the "in-addr.arpa" domain for IPv4 addresses or the "ip6.arpa" domain for IPv6 addresses.
Why Use Reverse DNS Lookup?
There are several reasons why you might want to perform a reverse DNS lookup:
- Identify Visitors - Website owners can use reverse DNS to identify organizations visiting their site based on IP addresses in their logs
- Troubleshoot Email Issues - Many mail servers check reverse DNS records to help filter spam
- Network Troubleshooting - Identify devices on a network by their IP addresses
- Security Research - Investigate suspicious IP addresses to determine their origin
- Shared Hosting Research - Find out what other domains are hosted on the same server as a particular website
How Reverse DNS Works
The reverse DNS system works by reversing the octets of an IP address and appending the special domain "in-addr.arpa" for IPv4 or "ip6.arpa" for IPv6. For example:
IPv4 Example:
For the IP address 192.0.2.1:
- Reverse the octets: 1.2.0.192
- Append in-addr.arpa: 1.2.0.192.in-addr.arpa
- Look up the PTR record for this domain
IPv6 Example:
For the IP address 2001:db8::1:
- Expand the address: 2001:0db8:0000:0000:0000:0000:0000:0001
- Reverse and separate each digit: 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2
- Append ip6.arpa: 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
- Look up the PTR record for this domain
Common Uses for Reverse DNS Lookup
Email Server Verification
Many email servers use reverse DNS as part of their spam filtering process. When an email server connects to deliver mail, the receiving server often performs a reverse DNS lookup on the sending server's IP address. If the lookup fails or doesn't match the domain the email claims to be from, the email might be flagged as potential spam.
Server Identification
System administrators often use reverse DNS to identify servers in logs. When a server connects to another server, the connection is typically logged with the IP address. A reverse DNS lookup can convert these IP addresses into more human-readable hostnames.
Security Analysis
Security professionals use reverse DNS lookups to gather information about potentially malicious IP addresses. The hostname associated with an IP can provide clues about the owner and purpose of the server.
Limitations of Reverse DNS
It's important to note that not all IP addresses have reverse DNS records. Setting up reverse DNS requires coordination between the IP address owner and their ISP or hosting provider. Additionally, a single IP address might host multiple domains (in shared hosting environments), but typically only one domain can be set as the reverse DNS record.