Netzwerk
Reverse IP Lookup
The reverse IP lookup tool finds the domain names associated with an IP address, including the PTR (reverse DNS) record and, where available, a list of other domains hosted on the same server. This is useful for investigating hosting relationships, identifying shared hosting environments, verifying PTR records for mail servers, and conducting security research.
What is Reverse IP Lookup?
Reverse IP lookup is the process of finding a domain name associated with a given IP address, as opposed to the forward lookup that maps a domain to an IP. There are two distinct operations: PTR record lookup, which queries the DNS system for the official reverse DNS entry of the IP (configured by the IP owner), and reverse hosting lookup, which searches a database of web crawls to find all domain names that resolve to the given IP address. Both are shown by this tool.
How does it work?
For PTR lookup, the tool queries the special in-addr.arpa DNS zone. For example, the PTR record for 8.8.8.8 is found by querying 8.8.8.8.in-addr.arpa. For reverse hosting lookup, the tool queries a third-party database that indexes which domains resolve to which IP addresses. Results include the PTR hostname, the number of domains found on the IP, and a list of those domains. Large shared hosting providers may have thousands of domains on a single IP.
Typical Use Cases
- Verifying the PTR record of a mail server IP to prevent email from being flagged as spam
- Investigating which other websites share a server with a suspicious domain
- Checking whether an IP belongs to a legitimate CDN or hosting provider
- Identifying hosting infrastructure during security reconnaissance
Step-by-step Guide
- Step 1: Enter an IPv4 or IPv6 address.
- Step 2: Click Lookup to perform the PTR query and reverse hosting search.
- Step 3: Read the PTR hostname for the official reverse DNS entry.
- Step 4: Review the list of co-hosted domains if available.
Example
Input
8.8.8.8
Output
PTR: dns.google. — Reverse hosting: No domains found (dedicated IP)
Tips & Notes
- A missing or mismatched PTR record is a common reason outbound email is rejected — ensure your mail server IP has a matching PTR and forward DNS entry.
- Shared hosting IPs may return hundreds of domains — use this to identify whether a target is on shared or dedicated infrastructure.
- ISP-assigned PTR records (e.g., 1-2-3-4.isp.net) indicate a residential or dynamic IP, which is often blocked by mail servers.
Frequently Asked Questions
Who controls the PTR record for an IP?
PTR records are managed by whoever is responsible for the IP block — typically the ISP or hosting provider, not the domain owner. To set a PTR record, you must contact your hosting provider or ISP and request them to add it.
Can I look up PTR records for IPv6 addresses?
Yes. IPv6 PTR records are stored in the ip6.arpa zone using the reversed nibble format. The principle is the same as IPv4 but the notation is more verbose.
Reverse IP Lookup
Find all domains hosted on an IP address using reverse DNS and hosting data.
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