The number next to your ISP name — and why it matters
When you look up an IP address — including your own at myipco.com — one of the fields shown is an ASN: a number like AS15169 or AS3320. Most people skip past it. That is a mistake, because the ASN tells you things about an IP that the ISP name alone does not.
The ASN (Autonomous System Number) identifies the network that owns and announces that IP address to the rest of the internet. It tells you whether an IP belongs to a residential ISP, a cloud provider, a VPN service, a university, or a government network — and that classification affects how websites treat your traffic.
This guide explains what ASNs are, how they work, and how to use the ASN field in an IP lookup to understand what any IP address actually represents.
What is an ASN?
An Autonomous System (AS) is a network — or a collection of networks — under a single administrative control with a unified routing policy. Every ISP, cloud provider, university, large corporation, and major hosting company that connects to the public internet operates at least one Autonomous System.
An Autonomous System Number (ASN) is the unique identifier assigned to each of these networks. ASNs are issued by Regional Internet Registries (RIRs) — the same organisations that allocate IP address blocks:
- ARIN — North America - RIPE NCC — Europe, Middle East, Central Asia - APNIC — Asia-Pacific - LACNIC — Latin America and the Caribbean - AFRINIC — Africa
ASNs were originally 16-bit numbers (AS1 through AS65535), which allowed 65,535 unique networks. As the internet grew, this ran out. Since 2007, 32-bit ASNs have been in use, extending the range to over 4 billion. You will sometimes see ASNs written as plain numbers (15169) or with the AS prefix (AS15169). Both refer to the same thing.
There are roughly 100,000 active ASNs globally as of 2026 — each representing a distinct network connected to the internet's routing infrastructure.
How ASNs work: BGP and the routing table
The internet is not a single network — it is tens of thousands of autonomous systems that agree to route traffic to each other. The protocol that makes this work is BGP (Border Gateway Protocol), sometimes called the "protocol that runs the internet."
Here is the basic mechanism:
Each AS announces its IP prefixes to its neighbours When an ISP acquires a block of IP addresses, it announces those addresses to its BGP peers: "I own 203.0.113.0/24 — send any traffic destined for those IPs to me." This announcement propagates across the internet until every major router knows to send traffic for that prefix to that AS.
BGP builds a map of AS paths Every BGP router maintains a table showing which ASNs traffic must pass through to reach any given IP block. When you load a webpage, your ISP's router looks up the destination IP, finds the AS path, and forwards the packet toward the destination AS.
Each AS sets its own routing policy An AS can choose which routes to accept from which peers, how to prioritise traffic, and whether to provide transit (forwarding traffic between other ASes). This is what "autonomous" means: each network makes its own routing decisions independently.
The practical consequence: your traffic crosses multiple AS boundaries on every internet request. A typical page load might route through your ISP's AS, a transit provider's AS, a CDN's AS, and finally the destination's AS — often 4–8 hops through different autonomous systems.
What the ASN in an IP lookup actually tells you
When you look up an IP address and see an ASN, you can learn several things that are more reliable than city-level geolocation:
The owning organisation ASN registration data is public. AS15169 is Google. AS16509 is Amazon (AWS). AS14061 is DigitalOcean. AS3320 is Deutsche Telekom. ASN-to-organisation mapping is authoritative — it comes from registry records, not inference.
The type of network ASNs fall into recognisable categories: - *Residential ISPs* — BT (AS2856), Comcast (AS7922), Verizon (AS701). Traffic from these ASNs looks like normal home users. - *Cloud providers* — AWS (AS16509), Google Cloud (AS396982), Azure (AS8075). IPs from these ASNs are almost certainly servers, not humans. Sites use this to flag bots or suspicious traffic. - *Hosting and data centres* — OVH (AS16276), Hetzner (AS24940), Linode (AS63949). Scraper detection and fraud systems routinely block entire hosting ASNs. - *VPN and proxy services* — Mullvad (AS39351), NordVPN (AS212238), ExpressVPN (AS3842). These ASNs are listed in VPN detection databases; streaming services and banks use them to flag or block VPN traffic. - *Universities and research networks* — JANET (AS786), Internet2 (AS11537). These have distinctive ASNs that help identify academic traffic. - *CDNs* — Cloudflare (AS13335), Fastly (AS54113), Akamai (AS20940). CDN ASNs appear frequently because much of the web is served through them.
Why the ASN is more reliable than the city IP geolocation at the city level is 50–80% accurate. The ASN and ISP fields are reliable because they come from registry records — there is no inference involved. If an IP belongs to AS16509, it belongs to Amazon. That is a fact, not an estimate.
This is why the ASN is the most useful field in an IP lookup for understanding what a particular IP actually represents.
How to look up any ASN
There are several ways to find the ASN for any IP address or organisation:
IP lookup tools The simplest method: enter the IP at myipco.com and the ASN is shown directly alongside the ISP name, country, and connection type. The result includes the full ASN number and the registered organisation name.
WHOIS lookup ASN registration records are publicly accessible through WHOIS. You can look up an ASN at myipco.com/whois — enter the ASN (e.g., AS15169) to see the full registration record including the organisation, date of allocation, and the IP address ranges announced under that ASN.
BGP route tables Tools like bgp.he.net (Hurricane Electric's BGP toolkit) or bgpview.io show which IP prefixes are announced by any ASN, the full routing path between two ASNs, and the AS's peering relationships. These are used by network engineers to debug routing issues and understand how traffic flows between specific networks.
Command line If you have a Unix-like system, `whois AS15169` queries the registry directly. `traceroute` output often shows ASN information inline. Network monitoring tools like mtr show the ASN for each hop as packets travel to a destination.
Why sites use your ASN to make decisions about you
ASN-based filtering is one of the most common and least-understood forms of IP-based access control.
VPN and proxy detection Netflix, BBC iPlayer, and most streaming services maintain lists of VPN provider ASNs and block them. When a VPN provider acquires a new IP range and begins routing through it, the ASN reveals who owns those IPs — even if the specific addresses are new. A VPN running on AS39351 (Mullvad) will be detected as a VPN regardless of which specific IP is assigned, because the ASN is the fingerprint of the network itself.
Bot and scraper detection E-commerce sites, financial services, and ticketing platforms block or rate-limit traffic from cloud provider and hosting ASNs (AWS, DigitalOcean, Hetzner). If a request comes from AS16509 (Amazon), it is unlikely to be a human customer — human customers use residential ISP ASNs like Comcast or BT. Automated systems (bots, scrapers, monitoring tools) typically run on servers in hosting ASNs.
Fraud risk scoring Payment processors and fraud detection systems assign risk scores based on ASN type. A purchase attempted from a residential ASN (expected) vs. a VPN ASN (slightly elevated risk) vs. a Tor exit node ASN (high risk) triggers different review thresholds. This is why some banks block VPN users from logging in.
Geo-restriction enforcement Beyond the country-level IP block, ASN data helps services distinguish between, say, a UK customer using a UK residential ISP (allowed) vs. a user connecting through a UK-based VPN server (blocked). The residential ISP ASN is part of what streaming services use to verify domestic access rights.
If you want to know how sites categorise your connection, the ASN field in myipco.com tells you exactly what network type you appear to be coming from.
ASNs and the structure of the internet
Understanding ASNs gives you a map of how the internet is actually organised — not as a flat network, but as a hierarchy of interconnected autonomous systems.
Tier 1 networks At the top are roughly a dozen Tier 1 providers — networks so large that they have settlement-free peering agreements with each other, meaning they exchange traffic without payment. These include AT&T (AS7018), Lumen/CenturyLink (AS3356), Telia (AS1299), and NTT (AS2914). They form the backbone of the global internet.
Tier 2 networks Regional ISPs and large national providers that buy transit from Tier 1 providers but also peer with other networks. Most major national ISPs fall in this category — they pay upstream for global connectivity but save costs by peering directly with local networks.
Tier 3 networks Local ISPs and smaller networks that purchase all their internet access from upstream providers. Residential ISPs in most countries operate at this level.
Internet Exchange Points (IXPs) Physical locations where ISPs, CDNs, and content providers connect their networks directly to exchange traffic without going through transit providers. DE-CIX in Frankfurt, AMS-IX in Amsterdam, and LINX in London are among the largest. When your traffic stays on local exchange infrastructure rather than routing through a US backbone, latency drops significantly.
Each ASN in a traceroute represents one of these tiers. The path your traffic takes — which ASes it crosses, which IXPs it touches — is visible to anyone running network diagnostic tools, and it reflects the commercial and physical architecture of the internet.
What your ASN reveals about you — and what it does not
Given that ASN data is public, accurate, and widely used for filtering, it is worth being clear about what it does and does not expose.
What the ASN reveals reliably: - Which ISP or network owns your IP address - Whether you are on a residential connection, a corporate network, a VPN, a hosting provider, or a mobile carrier - The country and sometimes the region associated with the network (more reliable than city-level geolocation) - Whether your IP is likely to be flagged or blocked by ASN-based filtering systems
What the ASN does not reveal: - Your identity — an ASN identifies the *network*, not the individual user within it. AS7922 (Comcast) has millions of customers. - Your precise physical location — ASN data is as accurate as registry records, which reflect network ownership, not user location. - Your browsing history — ASN is visible in every connection you make, but it is a single attribute, not a tracking identifier.
The distinction matters: many people worry about their IP address exposing who they are, when in practice the ISP name and ASN are far less identifying than browser fingerprinting signals that persist even through VPNs.
For a full picture of what your IP address exposes — including ASN, ISP, geolocation, and connection type — the IP lookup at myipco.com shows all of it in one place.