Explore notable Autonomous Systems.
An Autonomous System is a collection of IP networks under one administrative authority, identified by an ASN and announcing its prefixes to the global routing table via BGP. This directory covers researched ASNs with their announced prefixes, peer networks, routing data, and organization details.
Corrections welcome — see our editorial policy.
Browse every researched network.
What is an Autonomous System?
An Autonomous System Number (ASN) is a unique identifier assigned to a collection of IP networks under common administrative control. Every major ISP, CDN, cloud provider, university, and large enterprise that connects to the internet has one. When data travels from your device to a website, it crosses several autonomous systems along the way — each hop in a traceroute corresponds to a different ASN boundary.
AS15169 is Google. AS13335 is Cloudflare. AS7922 is Comcast. There are roughly 100,000 active ASNs globally, each announcing the IP prefixes they own to the global routing table via BGP (Border Gateway Protocol).
What does this tool show?
Enter an ASN we've profiled and you'll get a full profile: the organization that holds it, every IPv4 and IPv6 prefix currently announced to the global routing table, registered peer relationships split into upstream (transit providers) and downstream (customer networks), and the IANA block the ASN was assigned from. Each peer ASN is itself a link, so you can walk the routing graph one hop at a time. If you'd rather browse than search, the ASN directory lists every autonomous system we've researched, grouped by what the network is for.
Where does the ASN data come from?
Routing data comes from RouteViews, an academic BGP route-collector project, under CC BY 4.0. We parse its RIB dumps offline and publish what the collectors observed, so an ASN page describes a specific snapshot at a stated time — not a live query. Peer relationships are inferences from The CAIDA AS Relationships Dataset, which is published monthly and therefore carries its own, older date; an inferred relationship establishes no commercial arrangement between two networks. Registry block data comes from the IANA AS Numbers registry.
Two limits worth stating plainly. A route collector sees the internet through its own peers, so a network whose prefixes are not visible near those peers is under-counted rather than absent — roughly half the ASNs we publish announce nothing any collector observed, and their pages say so. And BGP data of any kind shows what is routed, which is not the same as what is allocated, in use, or legitimately held: an origin is not an owner.