---
title: "Look up ASN for an IP address"
method: GET
path: "/api/v1/asn/{ip}"
tags: ["ASN Lookup API"]
---

# Look up ASN for an IP address

`GET /api/v1/asn/{ip}`

Returns the Autonomous System Number, organization, network prefix, and datacenter classification for the given IP. Results are cached for 24 hours.

## Path parameters

- `ip` string, required

## Response `200`

ASN data retrieved successfully

- AsnLookupResponse
  - `ip` string, required
  - `asn` integer, nullable
  - `organization` string, nullable
  - `network` string, nullable
  - `is_datacenter` boolean, required
  - `country` string, nullable
  - `country_code` string

## Other responses

- `400` — Invalid IP address format
- `404` — No ASN data found for IP
- `429` — Rate limit exceeded

---

[API](https://skmtc.dev/ip-api/apis/ip-api-io-ip-geolocation-security-api.md) · [All operations](https://skmtc.dev/ip-api/apis/ip-api-io-ip-geolocation-security-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/ip-api/ip-api-io-ip-geolocation-security-api/revisions/a6862f586bf3/schema)