GLOSSARY · AUTONOMOUS SYSTEM NUMBER
ASN
An ASN is a unique number assigned to a network that manages its own routing on the internet, such as an internet provider, a cloud company, a university or a large business. Blocks of IP addresses are announced to the rest of the internet as belonging to a particular ASN.
Why it matters
The ASN tells you who runs the network behind an address. That is how services classify a visitor: an ASN belonging to a home internet provider suggests an ordinary user, while one belonging to a cloud or hosting company suggests a server. This classification, not the physical location, is what most VPN and proxy detection is built on.
In practice
Lookup databases pair each address with its ASN and the organisation's name, for example a number followed by a company. Free datasets can be out of date, and one company can hold several ASNs, so treat a match as evidence and not proof. Our IP lookup and VPN detector both show the ASN for any address.
Related terms
- ISP: An ISP is the company that connects you to the internet, whether through a cable, fibre, DSL, fixed wireless or mobile network.
- Datacenter proxy: A datacenter proxy runs on a server in a hosting facility, so its IP address belongs to a hosting or cloud company and not to a home or mobile provider.
- Residential proxy: A residential proxy sends your traffic through an IP address that a home internet provider assigned to a household.
- IP address: An IP address is a number that identifies a device or network connection on the internet, in the way a street address identifies a building.