What is ASN (Autonomous System Number)?

How ASNs work

Regional internet registries assign each autonomous system a number — originally 16-bit, later extended to 32-bit to keep up with growth. The AS uses that number in BGP announcements to tell the rest of the internet which IP prefixes it originates, and routers everywhere select paths expressed as chains of ASNs.

Autonomous systems come in recognizable types: consumer ISPs and mobile carriers (so-called eyeball networks), hosting and cloud providers, content networks, and transit backbones that carry traffic between them. Because routing data and registry records are public, anyone can map an IP address to its origin ASN, the owning organization, and the network's general character in milliseconds.

A single organization may operate several ASNs — one per region or acquisition — and one ASN may announce prefixes located in many countries, so the number identifies administrative control rather than geography.

Why ASNs matter for proxies and scraping

ASN classification is one of the first checks in modern bot detection. A request arriving from an ASN registered to a cloud or hosting company is scored as likely automation before any behavioral analysis happens, while the same request from a consumer ISP or mobile carrier ASN starts with far more trust. This single lookup explains much of the practical gap between datacenter and residential proxy performance.

ASN awareness also works in the other direction: targeting. Selecting exit IPs announced by a specific network lets you verify how a site behaves for customers of a particular ISP or carrier, test localization, or match traffic to an expected network profile. ProxyOmega's Platinum plan supports ASN targeting alongside country, state, and city filters.

Practical notes and common misconceptions

An ASN is not a location. One autonomous system can announce prefixes across many countries, and geolocation is a separate database lookup that can disagree with routing data. Nor does the number itself carry meaning — a low ASN just reflects an early registration.

Checking an address's ASN is easy with public WHOIS and route-lookup services, and the reputation databases used by anti-bot vendors maintain per-ASN risk categories that shift over time as networks are bought, repurposed, or abused.