ASN
An autonomous system number identifies the network that owns a block of IP addresses, and it is how sites tell a home connection from a data center.
An autonomous system is a network under one administrative control that announces its own routes to the rest of the internet, and its ASN is the number identifying it. Comcast has one. Hetzner has one. Vodafone has one. Every public IP address on earth sits inside exactly one of them, and which one is a matter of public record that anyone can query instantly.
It exists as routing plumbing and it has become, almost accidentally, the most consequential fact about any proxy address. When a site decides whether you look like a household or a server rack, the address itself barely matters. What it reads is the ASN, the organisation that owns the range. Hosting company, and you are a datacenter proxy. Consumer internet provider, and you are residential.
The classification is that direct, which explains something people find baffling. A brand-new, never-used address on a hosting provider's ASN is identified as hosted on its very first request, with no history and nothing to have done wrong. There was no detection involved and nothing to detect. It is a lookup against a table.
It also explains why rotation has a hard ceiling. Because reputation and classification attach to the network rather than to the individual address, cycling to a different IP inside the same flagged ASN presents the destination with a different number belonging to the same distrusted organisation. The network is the unit of trust, and you cannot rotate out of it by staying inside it.
Which makes ASN spread a genuine quality measure for a proxy pool, and one almost nobody asks about. Ten thousand addresses concentrated in a handful of autonomous systems are far more fragile than ten thousand spread across hundreds, because a site can act on the whole system in one rule. Pool size describes quantity; ASN diversity describes resilience.
One caveat on reading them: ASN ownership changes. Ranges are transferred, companies are acquired, and a network that was consumer ISP space last year can be hosting space now. Databases lag those changes, sometimes by a long way, which is why an address can be classified as one thing by one site and something else by another.
How HProxy handles it
We publish per-ASN liveness rather than one national figure, because the autonomous system is the real unit of trust and a claim about a country only means something broken down to the operators inside it. Two providers in the same country routinely behave nothing alike.
Frequently asked questions
How do I find the ASN of an IP address?
Any WHOIS or IP lookup service returns it, usually as AS followed by a number plus the owning organisation's name. Our own IP lookup shows it too. The information is public routing data, which is precisely why sites can use it so cheaply as a classification signal.
Why does my proxy get flagged as a datacenter even though it is new?
Because the classification is made on the ASN, not on the address's history. A fresh address inside a hosting provider's autonomous system is identified as hosted on its first request, having done nothing at all. Newness is irrelevant when the judgement is about who owns the range.
Does ASN diversity matter when choosing a proxy provider?
More than pool size does, and hardly anyone asks about it. Addresses concentrated in a few autonomous systems can be removed by a site in a handful of rules, while the same number spread across many systems has no single point of failure. It is the difference between a large pool and a resilient one.
Can an IP address change ASN?
Yes. Address blocks are transferred and companies are acquired, so a range that belonged to a consumer ISP can end up with a hosting provider or the reverse. Classification databases lag those transfers, sometimes considerably, which is one reason the same address is judged differently by different sites.
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