ASN Lookup
Find the Autonomous System Number, owner, and announced network prefixes for any IP address or ASN.
ASN Lookup Features
Discover network ownership and routing details for any IP or AS number.
AS Number Identification
Find the Autonomous System Number assigned to any IP address, helping you identify the network operator responsible for routing traffic.
Network Owner Details
Retrieve the organization name and holder information for any ASN, so you know who operates the network.
Announced Prefixes
View the IP address ranges (prefixes) announced by an Autonomous System through BGP, showing the full scope of their network.
Multiple Input Types
Look up by IP address, domain name, or ASN number directly. Domains are automatically resolved to their IP before querying.
How It Works
Three steps to look up ASN information for any IP or network.
Enter Your Query
Type an IP address (e.g. 1.1.1.1), a domain name (e.g. cloudflare.com), or an ASN number (e.g. AS13335) into the search field.
Query Network Databases
We query RIPE Stat and other network databases in real time to retrieve ASN ownership, announced prefixes, and routing information.
Review Network Info
View the AS number, holder name, prefix, RIR allocation, and the list of announced IP prefixes for the network.
Related Tools
More tools to investigate network infrastructure and domains.
Frequently Asked Questions
Common questions about Autonomous System Numbers and BGP routing.
An ASN is a unique identifier assigned to an Autonomous System (AS) — a network or group of networks under a single administrative policy. ASNs are used by the Border Gateway Protocol (BGP) to exchange routing information between networks on the internet. They are assigned by Regional Internet Registries (RIRs) such as ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC. For example, Cloudflare operates AS13335 and Google operates AS15169.
BGP (Border Gateway Protocol) is the routing protocol that connects Autonomous Systems on the internet. Each AS uses its ASN to announce the IP prefixes it is responsible for to neighboring networks. BGP routers use this information to determine the best path for traffic to reach its destination. When you see 'announced prefixes' in an ASN lookup, those are the IP ranges that the AS is advertising to the global routing table via BGP.
RIRs are organizations that manage the allocation and registration of IP addresses and ASNs within specific geographic regions. There are five RIRs: ARIN (North America), RIPE NCC (Europe, Middle East, Central Asia), APNIC (Asia-Pacific), LACNIC (Latin America and Caribbean), and AFRINIC (Africa). Each RIR maintains a database of network resource allocations in their region, which is the source data for ASN lookups.
ASN lookups are useful for network troubleshooting, security investigations, and understanding internet infrastructure. Network engineers use them to trace routing issues and verify peering relationships. Security analysts use ASN data to identify the network behind suspicious IP addresses. SEO professionals may check ASNs to understand hosting infrastructure. ISPs and CDN providers use ASN information for traffic engineering and capacity planning.