ASN Lookup
Look up ASN, network prefix, organization, ISP, and geolocation for an IP.
GET
/v1/asn
curl "https://dns.toolkitapi.io/v1/asn?ip=140.82.121.3"
import httpx
resp = httpx.get(
"https://dns.toolkitapi.io/v1/asn?ip=140.82.121.3",
)
print(resp.json())const resp = await fetch("https://dns.toolkitapi.io/v1/asn?ip=140.82.121.3", {
});
const data = await resp.json();
console.log(data);# See curl example
Response
200 OK
{
"ip": "140.82.121.3",
"asn": 36459,
"asn_name": "GITHUB",
"asn_description": "GitHub, Inc.",
"prefix": "140.82.112.0/20",
"country_code": "US",
"country_name": "United States",
"registry": "arin",
"city": "San Francisco",
"region": "California",
"org": "GitHub, Inc.",
"isp": "GitHub, Inc.",
"reverse_dns": "lb-140-82-121-3-iad.github.com",
"latitude": 37.7749,
"longitude": -122.4194,
"query_time_ms": 45.6
}Try It Live
Live Demo
Response
Description
Look up ASN, network prefix, organization, ISP, and geolocation for an IP.
How to Use
1
1. Pass an IPv4 address in the `ip` parameter. 2. Review the ASN, organization, and geolocation data.
About This Tool
ASN Lookup provides comprehensive IP intelligence: Autonomous System Number (ASN), network prefix, organization, ISP, geolocation (country, city, coordinates), registry, and reverse DNS. It uses Team Cymru DNS and ip-api.com for enrichment.
Why Use This Tool
- Threat intelligence — Identify the network and organization behind an IP
- Geolocation — Determine the geographic location of an IP address
- Network analysis — Map IP ranges to organizations and ISPs
- Abuse reporting — Find the responsible organization for abuse complaints
Frequently Asked Questions
What data sources are used?
Team Cymru DNS for ASN/prefix data and ip-api.com for geolocation enrichment.
How accurate is the geolocation?
City-level accuracy varies by region — typically accurate for major ISPs but may be off for VPNs, cloud providers, and mobile networks.
Start using ASN Lookup now
Get your free API key and make your first request in under a minute.