ASN Lookup

An Autonomous System Number (ASN) identifies a network on the internet that has its own routing policy: typically an ISP, hosting provider or large organisation. Networks announce their IP ranges to each other via BGP, and the ASN is how those announcements are attributed. Looking up the ASN behind an IP or domain tells you which operator actually hosts it.

Both. If you enter a domain, it is first resolved to its public IP address, and then that address is mapped to its ASN. If you enter an IP directly, it is looked up as-is. Private and reserved addresses are rejected, since they don't belong to any public autonomous system. The result shows the announced BGP prefix, country and registry alongside the AS number and operator name.

The lookup runs on Uptimeify's EU servers over a DNS-based ASN service, not in your browser, your input is used only to perform the lookup and is not stored. As an EU-built, EU-hosted provider, Uptimeify keeps this off US infrastructure and clear of US Cloud Act exposure, which matters for agencies handling client data under GDPR.