IP to ASN — API Reference

GET /api/v1/:ip

Resolves an IPv4 or IPv6 address to the ASN that announces it, returning the AS number and organisation name. Returns a 400 for invalid IPs and a 500 if the backend lookup fails.

Response fields

Field	Type	Description
ip	string	The queried IP address as provided.
announcedBy	object\|false	Object with `number` (integer) and `description` (string), or `false` if no announcing ASN was found.
error	null\|string	Null on success; error string on failure.

Example request

curl https://ip2asn.ipinfo.app/api/v1/1.1.1.1
curl https://ip2asn.ipinfo.app/api/v1/2606:4700::1111

Example response

{
  "ip": "1.1.1.1",
  "announcedBy": {
    "number":      13335,
    "description": "CLOUDFLARENET"
  },
  "error": null
}

GET /api/v1/@me

Redirects (302) to /lookup/{client_ip} so the result is served from Cloudflare's cache for that specific IP. A convenient shortcut — you don't need to know your own IP before making the request. The redirect response itself is never cached.

Example request

curl -L https://ip2asn.ipinfo.app/api/v1/@me

GET /lookup/:ip

Alias for /api/v1/:ip. Identical response. Exists for backwards compatibility and is the canonical cached URL used by the /@me redirect.

Example request

curl https://ip2asn.ipinfo.app/lookup/8.8.8.8

GET /lookup/@me

Alias for /api/v1/@me. Redirects (302) to /lookup/{client_ip}.

Example request

curl -L https://ip2asn.ipinfo.app/lookup/@me