Free IP address to ASN database
Downloadable, easy to parse, updated hourly.

Online lookup

IPv4 to ASN map

• Download ip2asn-v4.tsv (TAB-separated values)
• Download ip2asn-v4-u32.tsv (TAB-separated values, IPv4 addresses as 32-bit unsigned integers)

Format:

range_start range_end AS_number country_code AS_description

IPv6 to ASN map

• Download ip2asn-v6.tsv (TAB-separated values)

Format:

range_start range_end AS_number country_code AS_description

Combined IPv4+IPv6 to ASN map

• Download ip2asn-combined.tsv (TAB-separated values)

Format:

range_start range_end AS_number country_code AS_description

IPv4 to country code map

• Download ip2country-v4.tsv (TAB-separated values)
• Download ip2country-v4-u32.tsv (TAB-separated values, IPv4 addresses as 32-bit unsigned integers)

Format:

range_start range_end country_code

IPv6 to country code map

• Download ip2country-v6.tsv (TAB-separated values)

Format:

range_start range_end country_code

Public API

Subnet & ASN information about an IP:

https://api.iptoasn.com/v1/as/ip/<ip address>

Returns:

A JSON object:

{
  "announced": true,
  "as_country_code": "US",
  "as_description": "LEVEL3 - Level 3 Communications, Inc.",
  "as_number": 3356,
  "first_ip": "4.0.0.0",
  "last_ip": "4.23.87.255"
}