ASN Lookup
Look up an autonomous system number to see who operates it and which networks it announces.
Who owns a network
Every network on the internet belongs to an autonomous system. Enter an ASN or an IP and we show the operator, country, registry, allocation date and the full list of announced prefixes.
Announced prefixes
For every ASN you get the IPv4 and IPv6 prefixes it announces through BGP, so you see the whole address space of a provider, a cloud platform or a company at once.
From IP to ASN and back
Enter an IP address to find the network that announces it, or an AS number to list what it owns. The data come from public routing and registry sources and are cached briefly to keep answers fast.
Frequently asked questions
What is an ASN?
An autonomous system number identifies a network operated by one organization — an ISP, a cloud provider or a large company — that routes its own IP ranges on the internet.
Can I find the ASN of an IP address?
Yes. Enter any IP address and we look up the autonomous system that announces it.
What does an ASN look like?
ASNs are written as AS followed by a number, for example AS13335 for Cloudflare or AS15169 for Google. Numbers up to 4,294,967,295 are valid.
Why does an IP belong to a different ASN than my ISP?
Providers often lease address blocks to customers or announce them through an upstream network, so the announcing ASN can differ from the company you pay.