Reverse IP
Find other domains hosted on the same IP via a passive-DNS provider.
Data: passive DNS from Hackertarget's free tier. Coverage is sampled, not exhaustive — best for shared hosting and CDN edges, less reliable for one-off IPs. Per-server quota of ~100 lookups/day; results cached 24 h per IP, rate-limited 5/min per visitor.
Monitor this automatically
NetTests can run this check on a schedule, preserve historical results, compare changes over time, and alert you the moment something breaks.
Start monitoring free → See all monitoring productsFrequently Asked Questions
What is a reverse IP lookup?
A reverse IP lookup finds other domain names hosted on the same IP address. Unlike a PTR record (which gives the hostname assigned by the IP owner), this tool queries a passive DNS database to find all domains that have resolved to that IP — useful for shared hosting environments where hundreds of sites share one server.
How is this different from a PTR/rDNS lookup?
A PTR record is a single reverse DNS entry set by the IP owner — typically the server hostname like mail.example.com. A reverse IP lookup from a passive DNS database finds all domains that have pointed their A records to this IP, regardless of what the PTR record says. Shared hosting often has one IP with hundreds of domains, none of which appear in the PTR record.
What can I use this for?
Common uses: identifying co-hosted websites for security research, finding related infrastructure belonging to the same owner, understanding shared hosting environments, and investigating phishing or malware infrastructure. Knowing what else is on an IP helps assess neighbourhood reputation for email deliverability.
Why does the result show 'no results'?
Results come from a passive DNS database (HackerTarget free tier) which may not have seen all domains. Dedicated IPs, recently configured servers, or IPs with low DNS query volume may return no results. The free tier also has a limited result count — a popular shared hosting IP may be truncated at the API's result cap.