Query ASN details, IP prefixes, and BGP routing information
This free BGP & ASN Lookup turns a network identifier into routing intelligence. Enter an Autonomous System Number (for example AS15169) and the tool returns the AS name, description, country, the Regional Internet Registry (RIR) that allocated it, and the list of IP prefixes the network announces. Enter an IP address instead and it resolves which prefixes cover that address and which autonomous systems originate them, giving you the routing data behind any host on the public internet. In short, this free BGP ASN lookup answers two questions at once: what address space a network controls, and which network controls a given address.
The Border Gateway Protocol (BGP) is how independent networks — ISPs, hosting providers, enterprises — advertise the blocks of IP space they control and how to reach them. Each network is an Autonomous System identified by an ASN. For OSINT and infrastructure investigations, ASN and prefix data answers practical questions: which provider hosts a target, how large its address footprint is, which country and RIR it sits under, and whether several IPs share the same upstream operator.
For an ASN query, the name and description identify the operator, RIR shows the allocating registry (ARIN, RIPE NCC, APNIC, LACNIC, or AFRINIC), and the prefixes list every announced IP block — a rough measure of network size. For an IP query, review the announced prefixes and their originating AS numbers to see who routes that address. Routing data reflects live global routing tables and can change frequently, so treat a result as a point-in-time snapshot rather than a permanent assignment.
Once you know the autonomous system behind a host, pivot with the IP address geolocation lookup to place individual addresses, the WHOIS and RDAP domain lookup to tie names to that infrastructure, and the domain DNS and email-security scanner to map services running on it.
An Autonomous System Number uniquely identifies a network that controls its own IP address blocks and routing policy on the internet. ISPs, hosting companies, and large enterprises each have one or more ASNs, written in the form AS15169.
Yes. Enter an IP address and the tool returns the prefixes that cover it and the autonomous systems announcing those prefixes, so you can identify the operator hosting a given address. You can also enter an ASN directly to see that network's full prefix list.
The RIR is the Regional Internet Registry that allocated the resource — ARIN (North America), RIPE NCC (Europe/Middle East), APNIC (Asia-Pacific), LACNIC (Latin America), or AFRINIC (Africa). It is a strong indicator of the region where a network is administratively based.