What is an ASN? Autonomous systems explained
The number that identifies who actually runs a piece of the internet — and what it reveals about an IP.
The internet is a network of networks
The internet isn't one big system — it's thousands of independent networks (ISPs, hosting companies, universities, cloud providers, big tech firms) all interconnected. Each of these networks needs a way to be identified so traffic can be routed between them. That identifier is an ASN — an Autonomous System Number.
What an ASN actually is
An autonomous system (AS) is a collection of IP addresses managed under a single organization with one consistent routing policy. Its ASN is the unique number assigned to it, written like AS7922 (Comcast) or AS15169 (Google). Think of it as a network's official ID in the internet's routing system — the way a phone area code identifies a region, an ASN identifies a network.
When data travels across the internet, it hops from one autonomous system to another until it reaches its destination. The networks announce to each other "I can reach these IP ranges" using their ASNs, via a protocol called BGP (Border Gateway Protocol). You don't need to know BGP's details — just that ASNs are how networks tell each other where traffic should go.
Why an ASN matters (what it reveals)
For an ordinary person checking an IP, the ASN and its organization answer a surprisingly useful question: who really runs this connection? That's more revealing than it sounds:
- The operator's identity — the AS organization names the ISP, host, or company behind an IP. This is often clearer than the "ISP" label alone.
- Residential vs. hosting vs. mobile — this is the big one. An IP belonging to a consumer ISP's ASN looks like a normal home user. An IP belonging to a hosting/data-center ASN (like a cloud provider) is a server — which is what VPNs, bots, scrapers, and automated traffic typically run on. A mobile carrier's ASN means a phone network. Sites use this signal constantly: to flag suspicious logins, decide whether to show a CAPTCHA, or detect VPN traffic.
- Routing footprint — large networks hold multiple ASNs and huge IP ranges; the ASN hints at the scale and type of the operator.
An honest caveat about "connection type"
Classifying an IP as residential, hosting, or mobile is an educated inference, not a hard fact. It's usually derived from the operator's name and public databases, and it can be wrong — a legitimate business connection might look unusual, and some networks blur the lines. Treat the connection-type label as a strong hint, not proof. The ASN and operator name themselves are generally reliable; the interpretation around them is informed guesswork.
Who assigns ASNs?
ASNs are handed out by the Regional Internet Registries (RIRs) — the same bodies that allocate IP address blocks (ARIN for North America, RIPE for Europe, APNIC for Asia-Pacific, and others). An organization that needs to run its own independent routing applies for an ASN and the IP ranges that go with it. This is all public information, which is why tools can look it up.
How to check an IP's ASN
You can see the autonomous system behind any IP — including your own — right here:
- Open the ASN & Routing tool on GetNetStats. Your own IP is filled in by default; paste any other IP to analyze it instead.
- You'll see the ASN, the operator, a best-effort connection-type estimate, and the reverse-DNS hostname.
- It runs in your browser using public routing data — nothing stored, no sign-up.
A useful experiment: check your home IP, then check a public one like 8.8.8.8 (Google's DNS). Yours will likely show your ISP's ASN classified as residential; Google's will show a hosting/data-center ASN — a clear illustration of how ASNs distinguish a home connection from a server.
Check an IP's ASN
Try it now with the ASN & Routing tool — see the network behind any IP address.