ASN lookup

An ASN, or autonomous system number, is the number a network operator uses to announce its IP addresses to the rest of the internet. It is written AS followed by digits, such as AS7922. Every network that connects to the internet on its own terms has one, and the registry that issued it records the operator's name and country.

Type the IPv4 address into the box at the top of this page and press Look up. The answer names the AS number that announces the block holding that address, the name it is registered under and its country. This lookup reads IPv4 only, and it refuses private and reserved addresses because no network announces those to the internet.

An ISP is a company that sells internet access. An ASN is a number that identifies one network on the internet. An ISP usually runs one or more of them, and a business, a university or a hosting company can have one without selling access to anyone. So an AS number tells you who announces an address, which is not always the company that serves the person using it.

Operators grow by merging, and each network they buy keeps the number it had. A company can also keep a separate number for each region, for its mobile network or for its business customers. Charter, for example, appears in the dataset under several numbers named after the cable companies it absorbed, and each has its own page in the list below.

The data is the public iptoasn.com dataset, which we refresh about once a month, and the page prints the date it was read. A block that moved to a new operator, or a network that started announcing addresses since then, may not show yet.

Yes, on every pool: Essential and Premium Residential, and Mobile. A request can ask for one network by AS number with the asn option, written AS7922 or 7922. If no exit on that network is available, the request fails rather than falling back to another network. We do not publish which networks are available at a given time. See Essential and Premium and the API reference.