IP Ownership Look Up
Related tools
What this is
Every public IP belongs to a network (identified by an ASN — Autonomous System Number) and is allocated through a regional registry (RIR). This lookup reports both: who operates the network and how the block is registered.
How to read your result
The ASN line names the operator (e.g. a cloud provider) and the announced prefix; the registry line shows the formal allocation. Use it to answer "whose infrastructure is this really?"
Common problems and how to fix them
Mail server IP belongs to a consumer/generic cloud range
How it shows up: Receivers distrust the IP by default; deliverability is poor despite correct SPF/DKIM/DMARC.
How to fix it: Send outbound mail through a reputable relay service, or use dedicated IP offerings designed for mail. Reputation follows the IP range as much as your domain.
Unknown IP appears in logs or in your DNS records
How it shows up: Traffic or records point somewhere you do not recognize.
How to fix it: Look up the ASN and registry data to identify the operator; for abuse, the registry entry lists the responsible contact. Update or remove any of your DNS records still pointing at infrastructure you no longer control.
Related reading
- Who Owns This IP? Reading ASNs, Registries, and Network AllocationsA plain guide to IP ownership: how ASNs and Regional Internet Registries work, what an IP ownership lookup actually tells you, and where to take it next.
- PTR Records and Reverse DNS: What They Are and Why Your Mail Depends on ThemHow reverse DNS and PTR records work across IPv4 and IPv6, who actually controls them, and why mail servers use FCrDNS to decide whether to trust your IP.
- Mapping Subdomains with Certificate Transparency LogsHow the CT Subdomain Resolver reads public certificate logs to find forgotten subdomains, resolve their live IPs, and audit your real attack surface.
Frequently asked questions
- What does the IP Ownership tool show?
- It reveals who is responsible for an IP address: the organization that holds it, its Autonomous System Number (ASN) and the network block (CIDR) it belongs to. This data comes from RDAP, the official registry lookup protocol used by the regional internet registries.
- How do I use this tool?
- Enter an IPv4 or IPv6 address and run the lookup; the query is sent to RDAP server-side and the owner, ASN and network range are returned. Nothing you enter is stored.
- Why does knowing IP ownership matter?
- It helps you identify where traffic or an abuse attempt actually originates, attribute it to a hosting provider or ISP, and find the right abuse contact. It is also useful for verifying that an IP belongs to a service you expect.
- How do I read the ASN and network fields?
- The ASN identifies the network operator that announces the address on the internet, while the network (CIDR) shows the full block that the IP was allocated within. The owner name is the organization that registered that block with the registry.
- Why might the owner be a hosting provider and not the real user?
- RDAP shows the entity the address is registered to, which is usually the ISP, hosting company or cloud provider rather than the individual customer using it. For content or cloud IPs the listed owner is the infrastructure operator, not the website or person behind the service.