ASN Lookup
Instant results.
Find the Autonomous System Number, organization, and network prefix for any IPv4 or IPv6 address. Powered by MaxMind GeoLite2-ASN. Includes datacenter and hosting detection.
What Is an Autonomous System Number?
An Autonomous System Number (ASN) is a globally unique identifier assigned to a group of IP prefixes managed by one or more network operators under a single, clearly defined routing policy. The internet is not one network — it is tens of thousands of autonomous systems exchanging routing information with each other using the Border Gateway Protocol (BGP).
When your browser sends a request to a server, BGP tables built from ASN announcements determine the path your packets take across the internet. Each ASN announces the IP prefixes it "owns" to neighboring networks, and routers worldwide use this information to forward traffic to the right destination.
ASNs are assigned by the five Regional Internet Registries (RIRs): ARIN (North America), RIPE NCC (Europe/Middle East/Central Asia), APNIC (Asia-Pacific), LACNIC (Latin America), and AFRINIC (Africa). An organization typically applies for an ASN when it operates a network that exchanges routing information with two or more upstream providers (multi-homing), or when it provides transit to other networks.
BGP Routing
ASNs use BGP to announce IP prefixes they own to neighboring networks, building the global internet routing table.
5 Regional Registries
ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC assign ASNs to organizations in their respective geographic regions.
Fraud Detection
Datacenter ASNs (AWS, DigitalOcean) often indicate VPN or proxy usage. Residential ASNs signal genuine end-user traffic.
IP Prefixes
Each ASN announces one or more IP prefixes (CIDR blocks) it controls, from small /24 blocks to massive /8 allocations.
Major ASN Reference
Well-known Autonomous Systems operated by the world's largest internet organizations. Recognizing these ASNs helps classify traffic and build smarter fraud rules.
| ASN | Organization | Type | Region |
|---|---|---|---|
| AS15169 | Google LLC | Cloud / CDN | Global |
| AS13335 | Cloudflare, Inc. | CDN / DNS | Global |
| AS16509 | Amazon Web Services | Cloud | Global |
| AS8075 | Microsoft Corporation | Cloud / CDN | Global |
| AS32934 | Meta Platforms, Inc. | Cloud / Social | Global |
| AS20940 | Akamai Technologies | CDN | Global |
| AS14061 | DigitalOcean, LLC | Hosting / VPS | Global |
| AS63949 | Akamai Connected Cloud (Linode) | Hosting / VPS | Global |
| AS7922 | Comcast Cable Communications | ISP / Residential | North America |
| AS3215 | Orange S.A. | ISP / Residential | Europe |
| AS4134 | China Telecom | ISP / Residential | Asia-Pacific |
| AS174 | Cogent Communications | Tier-1 Transit | Global |
| AS3356 | Lumen Technologies (CenturyLink) | Tier-1 Transit | Global |
| AS9009 | M247 Europe SRL | VPN / Hosting | Europe |
ASN Lookup API & Code Examples
A single GET request returns ASN, organization, network prefix, and datacenter classification. Predictable JSON — no parsing quirks.
GET /api/v1/asn/{ip}?api_key={key}
curl "https://ip-api.io/api/v1/asn/8.8.8.8?api_key=YOUR_API_KEY"
{
"ip": "8.8.8.8",
"asn": 15169,
"organization": "GOOGLE",
"network": "8.8.8.0/24",
"is_datacenter": true,
"country": "United States",
"country_code": "US"
}
GET /api/v1/asn/{ip}?api_key={key}
const res = await fetch(
"https://ip-api.io/api/v1/asn/8.8.8.8?api_key=YOUR_API_KEY"
);
const data = await res.json();
console.log(`AS${data.asn} — ${data.organization}`); // AS15169 — GOOGLE
console.log(data.is_datacenter); // true
{
"ip": "8.8.8.8",
"asn": 15169,
"organization": "GOOGLE",
"network": "8.8.8.0/24",
"is_datacenter": true,
"country": "United States",
"country_code": "US"
}
GET /api/v1/asn/{ip}?api_key={key}
import requests
res = requests.get(
"https://ip-api.io/api/v1/asn/8.8.8.8",
params={"api_key": "YOUR_API_KEY"}
)
data = res.json()
print(f"AS{data['asn']} — {data['organization']}") # AS15169 — GOOGLE
print(data['is_datacenter']) # True
{
"ip": "8.8.8.8",
"asn": 15169,
"organization": "GOOGLE",
"network": "8.8.8.0/24",
"is_datacenter": true,
"country": "United States",
"country_code": "US"
}
GET /api/v1/asn/{ip}?api_key={key}
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,
"https://ip-api.io/api/v1/asn/8.8.8.8?api_key=YOUR_API_KEY");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$data = json_decode(curl_exec($ch));
echo "AS{$data->asn} — {$data->organization}"; // AS15169 — GOOGLE
{
"ip": "8.8.8.8",
"asn": 15169,
"organization": "GOOGLE",
"network": "8.8.8.0/24",
"is_datacenter": true,
"country": "United States",
"country_code": "US"
}
GET /api/v1/asn/{ip}?api_key={key}
require 'net/http'
require 'json'
uri = URI('https://ip-api.io/api/v1/asn/8.8.8.8')
uri.query = URI.encode_www_form(api_key: 'YOUR_API_KEY')
res = Net::HTTP.start(uri.hostname, use_ssl: true) { |h| h.get(uri) }
data = JSON.parse(res.body)
puts "AS#{data['asn']} — #{data['organization']}" # AS15169 — GOOGLE
{
"ip": "8.8.8.8",
"asn": 15169,
"organization": "GOOGLE",
"network": "8.8.8.0/24",
"is_datacenter": true,
"country": "United States",
"country_code": "US"
}
ASN Lookup FAQs
Common questions about Autonomous System Numbers and BGP routing.
What is an ASN (Autonomous System Number)?
An Autonomous System Number (ASN) is a globally unique number assigned to a group of IP prefixes managed by one or more network operators under a single, coherent routing policy. ASNs are used in BGP (Border Gateway Protocol) to identify networks on the internet. Examples: AS15169 (Google), AS13335 (Cloudflare), AS16509 (Amazon Web Services).
How do I find the ASN for an IP address?
Enter any IPv4 or IPv6 address into the lookup tool above and click "Look Up ASN." The tool
returns the ASN number, organization name, network prefix (CIDR), and whether the IP belongs to a
datacenter. For programmatic access, use GET https://ip-api.io/api/v1/asn/{ip}
with your API key.
What's the difference between an ASN and an IP address?
An IP address identifies a single device (or NAT boundary) on the internet. An ASN identifies an entire network or group of networks operated by one organization. One ASN can encompass millions of IP addresses. IP addresses tell you where traffic goes; the ASN tells you who controls the network that routes that traffic.
Who assigns ASNs?
ASNs are assigned by five Regional Internet Registries (RIRs) under the coordination of IANA: ARIN (North America), RIPE NCC (Europe, Middle East, Central Asia), APNIC (Asia-Pacific), LACNIC (Latin America & Caribbean), and AFRINIC (Africa). Organizations apply to their regional RIR when they need to exchange routing information with multiple upstream providers.
Can a company have multiple ASNs?
Yes. Large organizations often operate multiple ASNs for different regions, subsidiaries, or service categories. Amazon uses AS16509 for AWS, but also maintains several other ASNs for different parts of its infrastructure. Google, Meta, and Microsoft each operate dozens of ASNs globally. Each ASN represents a distinct autonomous system with its own routing policy.
How is ASN data useful for fraud detection?
ASN data reveals who controls the network an IP belongs to, which is a powerful fraud signal. Datacenter and hosting ASNs (DigitalOcean, AWS, Vultr) are frequently used by fraudsters to mask their location via VPNs or proxies. Legitimate users typically connect from residential ISP ASNs. Combine ASN classification with our Fraud Detection API for complete risk scoring.
What is BGP?
BGP (Border Gateway Protocol) is the routing protocol that connects autonomous systems on the internet. Each ASN uses BGP to announce the IP prefixes it controls to neighboring networks. Routers worldwide maintain BGP tables built from these announcements, enabling them to forward packets to the correct destination across thousands of interconnected networks. BGP is often called "the protocol that holds the internet together."
Is your ASN lookup tool free?
Yes, the interactive ASN lookup tool on this page is completely free with no sign-up required.
Programmatic API access (GET /api/v1/asn/{ip}) requires a paid subscription.
Anonymous users can make limited requests via the tool directly from this page.
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Know who's behind any IP address
Query ASN number, organization, network prefix, and routing data in one simple API call.