Find the Hostname Behind an IP
Reverse IP & PTR Lookup
Query the PTR record for any IP address to discover its reverse DNS hostname — essential for email deliverability and network troubleshooting.
Frequently Asked Questions
What is a reverse IP lookup?
A reverse IP lookup (also called reverse DNS or rDNS) maps an IP address back to a hostname. It queries the PTR record in DNS for the reversed IP under the in-addr.arpa domain. For example, to look up 1.2.3.4, it queries 4.3.2.1.in-addr.arpa for PTR records.
What is a PTR record?
A PTR (Pointer) record is a DNS record that maps an IP address to a hostname. It's the opposite of an A record. PTR records are commonly used for email server verification — many mail servers check that the sending IP has a valid PTR record matching the server's hostname.
Why would an IP not have a PTR record?
Not all IP addresses have PTR records configured. The IP's owner (usually the ISP or hosting provider) must explicitly set up the reverse DNS entry. Residential IPs often have generic PTR records set by the ISP, while some IPs may have no PTR record at all.
Why is reverse DNS important for email?
Email servers often perform reverse DNS lookups on the sending server's IP to verify its identity. If the PTR record doesn't match the HELO/EHLO hostname or is missing entirely, the receiving server may flag the email as spam or reject it outright.
Can I enter a domain instead of an IP?
Yes! If you enter a domain name, the tool will first resolve it to an IP address using a DNS A record lookup, then perform the reverse lookup on the resolved IP.
Complete Guide: How to Use the Reverse IP Lookup
Find all domains hosted on a specific IP address with our reverse IP lookup tool. This reveals shared hosting environments, identifies related websites, and helps map web infrastructure. Useful for security research, competitive analysis, and server administration.
Step-by-Step Instructions
- 1
Enter an IP address
Type the IP address you want to investigate (e.g., 104.21.56.78). You can also enter a domain to first resolve it to an IP.
- 2
Run the reverse lookup
The tool queries databases to find all domains resolving to this IP address.
- 3
View hosted domains
See the list of all domains sharing this IP, along with any available details like title or status.
- 4
Analyze the results
Determine if the IP hosts many sites (shared hosting) or few (dedicated/VPS). Use this information for your analysis.
Common Use Cases
- ✓Security research — discover other domains on the same server that might be vulnerable
- ✓Competitive analysis — find related websites owned by the same organization
- ✓Shared hosting audit — check who else shares your server (noisy neighbors can affect performance)
- ✓Incident response — identify all potentially affected domains when an IP is compromised
- ✓Reconnaissance — map out an organization's web infrastructure
- ✓IP reputation — understand why an IP might be blacklisted by checking what sites it hosts
Pro Tips
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