ASN Lookup
Find out which network an IP address belongs to. Enter an IP to discover its autonomous system number, the announcing prefix and the registry that allocated it, or enter an ASN to see who owns it and where it is registered.
How to Use
Paste an IPv4 or IPv6 address to look up its origin network, or type an ASN such as AS15169 to look up the organisation behind it. The tool queries Team Cymru's public DNS service, so it works from any network without an API key.
- IP address to ASN and announcing prefix
- ASN to organisation name and registry
- IPv4 and IPv6 support
- Registry and allocation date
- Raw DNS response available
What an ASN is
An autonomous system is a collection of IP networks operated by a single organisation under one routing policy. The internet's routing table is built from routes between these systems, so knowing which AS owns an address tells you which network traffic to it actually travels through — useful for diagnosing routing, geo-blocking and abuse reports.
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