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IP to ASN lookup

Find the network that announces an IP address: its AS number, owner, prefix and country. Or enter an AS number to see who it belongs to.

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How it works

The internet is made of thousands of networks, each run by one organisation: an internet provider, a cloud company, a university. Each network has a number, its AS number (ASN, for autonomous system number). Networks tell each other which blocks of addresses, or prefixes, they carry. This is called announcing a prefix.

This lookup asks Team Cymru's free IP to ASN service which network announces the address, and in which prefix. It also shows the country and the regional registry (such as ARIN or RIPE NCC) that handed out the addresses, and the address's reverse DNS name.

For email, the network tells you who really runs a sending server. Blocklists and receivers also judge reputation by network, so mail from a network with a bad name can suffer even if your own IP is clean. Check an IP's listings with the blocklist check and its reverse DNS with the PTR check.