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ASN

published · September 10, 2026

An Autonomous System Number identifies one network that announces its own routes to the internet under a single routing policy.

An Autonomous System Number identifies one network that announces its own routes to the internet under a single routing policy. Every address on the public internet belongs to exactly one at a time, and the AS is the closest thing to an answer to "whose network is this?".

What Spaw answers

asn is the number, org the organisation that holds it, and asn_type the kind of network it is: hosting, ISP, business, education, government or similar. Three registry facts sit beside them — registry, registry_country and allocated_at, the date the block was allocated.

asn_type is what most policies actually want. A signup from a hosting AS is a different thing from a signup from a consumer ISP, and the type says which without anyone having to keep a list of cloud providers.

What it does not say

An AS belongs to an operator, not to a person. On a hosting, VPN or relay network the country, the city and the organisation are the operator's, and the risk score's country comparisons are withheld for that reason. Nothing about an ASN identifies who is using the address.

Related

markdown version: /glossary/asn.md

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