What Is an ASN? (And How to Find Out Who Owns an IP Address)

If you have ever wanted to know who is behind an IP address, which company runs it, what network it belongs to, and where it sits, the answer runs through something called an ASN. This guide explains what an ASN is and walks through finding the owner of any IP. You can jump straight in with the ASN Lookup lookup and IP Information information tools.

"Internet" literally means inter-network, thousands of independently run networks stitched together. Each large network, whether an ISP, a cloud provider, a university, or a big company, is called an Autonomous System: a collection of IP addresses under a single administrative control with its own routing policy. Every such system gets a unique Autonomous System Number, like AS15169 for Google or AS13335 for Cloudflare.

ASNs are how networks announce to the rest of the internet that certain IP ranges are reachable through them. The protocol that carries those announcements between networks is BGP (Border Gateway Protocol). So the chain of ownership runs from an IP address, to the IP range (prefix) that contains it, to the ASN that announces that prefix, to the organization that operates the ASN.

Look up an ASN with the ASN Lookup tool and you will typically see the organization that operates it, the country of registration, and the Regional Internet Registry that allocated it, which is one of ARIN, RIPE, APNIC, LACNIC, or AFRINIC. You will often also see the IP prefixes the system announces.

This is how you tell a residential ISP from a data center, a cloud host from a corporate network, or one carrier from another. That distinction matters constantly in security and analytics work, where data-center or VPN traffic behaves very differently from genuine residential users.

There are a few complementary methods, and using them together gives the fullest picture. The fastest is an IP information lookup: paste the address into the IP Information tool and it returns the geolocation, the ISP or organization, and the ASN in one step, which answers most "who is this?" questions on its own. A WHOIS Lookup lookup on the IP returns the registry record for the address block, including the organization it is allocated to, the network range, and abuse contact details, which is the authoritative ownership record.

A Reverse DNS (PTR) lookup turns the IP back into a hostname if one is published, and hostnames often reveal the provider and even the location through a city code or a tag like "ec2" for AWS. Finally, once you know the ASN, looking it up directly with the ASN Lookup tool shows the operating organization and its other IP ranges, which is handy when you want to know everything one network controls.

Say a login alert shows a sign-in from 8.8.8.8 and you want to understand it. The IP Information tool shows the location and that the address belongs to AS15169, Google LLC. A WHOIS Lookup lookup confirms the block is registered to Google with an abuse contact. A Reverse DNS (PTR) lookup resolves it to dns.google.

Now you know it is Google's public DNS service, not a random attacker. That same three-step pattern, IP information then WHOIS then reverse DNS, works for any address you are trying to identify.

Knowing how to map an address to its operator is useful well beyond curiosity. In security and abuse handling it lets you identify where suspicious traffic originates and find the right contact to report it to. During troubleshooting, looking up each hop's ASN in a Traceroute shows which carriers your traffic crosses and where a problem sits.

It also supports filtering and analytics, since distinguishing data-center and VPN traffic from residential users is central to fraud and bot detection, and it helps with due diligence when you want to confirm a service is hosted where it claims to be.

What is the difference between an IP, a prefix, and an ASN? An IP is a single address, a prefix such as 8.8.8.0/24 is a block of addresses, and an ASN is the network that announces one or more prefixes to the internet. One organization can hold many prefixes under one ASN.

Can I find a person's name from an IP's ASN? No. ASN and WHOIS records identify the organization operating the network, usually an ISP or host, not the individual end user. Only the ISP can link an IP to a subscriber, and that requires legal process.

How do I find every IP range a company owns? Look up their ASN with the ASN Lookup tool, which lists the prefixes that system announces. Large organizations may operate several ASNs.

Is an ASN the same as an IP address? No. An ASN identifies a network operator, while an IP address identifies a host on a network. They are linked but separate, and the IP Information tool shows both for any address.