Reverse IP Lookup
See what an address says about itself — and check which domains point at it.
What this tool does
The PTR record
The name the address holder publishes for it, which usually identifies the hosting provider.
Network owner
The autonomous system announcing the address, and the prefix it sits in.
Verify specific domains
Paste names and each is resolved and compared against the address — an exact answer to the question people usually actually have.
Clear about the limit
Listing every co-hosted domain needs a commercial passive-DNS dataset. That is stated rather than approximated.
Frequently asked questions
Can this list every domain hosted on an IP address?
No, and no free tool can do it honestly. DNS is a one-way lookup: names point at addresses, and there is no public index running the other way. Services that list co-hosted domains are querying a passive-DNS dataset — a commercial product built by recording DNS answers at scale. This tool does the parts that public data genuinely answers and verifies domains you supply, rather than presenting a partial list as complete.
What does the PTR record tell me?
The name the address holder chose to publish for it — often revealing the hosting provider and sometimes the specific machine. It is set by whoever controls the IP block, not by domain owners, so a shared host usually shows the provider's own naming rather than any customer site.
How do I check whether a specific domain is on this IP?
Paste the domains into the verification box. Each is resolved and compared against the address, which answers the question exactly rather than approximately. That covers the common real cases: confirming a migration completed, or checking which of your own sites share a server.
Why did a domain I expected not match?
Usually because it has several addresses. Large sites round-robin across many IPs and CDNs return different addresses by region, so resolving from here can legitimately return an address different from the one you had in mind. The addresses actually returned are shown so you can see what happened.
What is this useful for?
Identifying the provider behind an address, confirming a DNS migration reached the new server, checking whether your sites share infrastructure, and — during incident response — establishing which network an address belongs to before deciding what to do about it.
Is there a free way to find subdomains instead?
Yes, and it works well: Certificate Transparency logs record every certificate a public CA issues along with the hostnames it covers. The subdomain finder on this site reads them, which is real evidence rather than guesswork.
Monitor it, don't just check it
One-off checks catch what is broken today. CertNotify watches your certificates, domains, DNS and code continuously and tells you before something breaks.