What is an ASN — Autonomous System Number

An ASN (Autonomous System Number) is a unique number of an autonomous system — a network or group of networks under a single administrative control that participates in Internet routing. Numbers are issued by regional registries and look like values such as AS13335.

An ASN often reveals the ISP or cloud egress behind an IP: for example, ASN 13335 usually means Cloudflare, and major carriers own their own numbers. This helps understand who serves an address before you know its exact location.

Don't confuse an ASN with geolocation: the number describes a network, not a physical point. City and coordinates are estimated separately from geo databases. The ToolsHelper IP lookup shows the ASN, organization, and country for any address.

An autonomous system number identifies a network operator on the public internet, not your street address. AS15169 is one of Google’s. The lookup shows the number next to the IP when a provider returns it. It does not prove who sat at the keyboard. Private addresses such as 10.0.0.1 have no public ASN. This page defines the number. The IP tool is where you paste an address.