Free BGP AS lookup. Enter an ASN or IP to get the AS holder, RIR, country, abuse contact and every announced IPv4/IPv6 prefix. Live RIPEstat data.
This free BGP AS lookup tool resolves an autonomous system number to the organisation that operates it, and resolves an IP address to the AS that announces the prefix containing it. Enter AS15169, 15169, or 8.8.8.8 and you get the AS holder name, registering RIR, country, registry last-updated date, abuse and technical contacts, website, IPv4 and IPv6 prefix counts, and the full list of prefixes the AS announces into the global routing table. Data comes live from the RIPEstat API, the public data service run by RIPE NCC, which aggregates routing and registry information from all five regional internet registries — not just RIPE’s own region.
An autonomous system is the unit of routing policy on the internet. Every network that speaks BGP to another network — an ISP, a hosting provider, a CDN, a large enterprise with multiple upstreams — holds an AS number and uses it to announce which IP prefixes it can reach. When you look up an ASN you are asking, in effect, “who runs this chunk of the internet, and what address space do they claim?”
AS prefix. The tool queries the AS overview and whois records and returns the holder, description, country, RIR, registry date, contact addresses, and prefix counts. If the AS exists in the registry but announces nothing in BGP, you are told that explicitly — a meaningful distinction when investigating dormant or hijacked resources.Input mode is auto-detected, so a string starting with AS or consisting only of digits is treated as an ASN, and a valid IPv4 or IPv6 literal is treated as an address. Recent lookups are kept in your browser so you can jump back to an AS you were just examining, and results export as JSON or CSV for pasting into a report or feeding to a script.
“What is the BGP AS number range?” is one of the most common questions about autonomous systems, and the answer changed materially in 2007 when 32-bit ASNs were introduced. The allocation map today:
| Range | Type | Notes |
|---|---|---|
| 0 | Reserved | Must not appear in an AS path; used to mark “not routed” in some contexts. |
| 1 – 64495 | Public 16-bit | Globally unique, assigned by RIRs to real networks. |
| 64496 – 64511 | Reserved | Set aside for documentation and sample code. |
| 64512 – 65534 | Private 16-bit | Usable inside an organisation; must be stripped before announcements reach the public internet. |
| 65535 | Reserved | Last 16-bit value, reserved. |
| 23456 | AS_TRANS | Placeholder used so 32-bit-unaware routers can carry paths containing 32-bit ASNs. |
| 65536 – 4199999999 | Public 32-bit | The expanded space; RIRs now hand these out routinely. 65536–65551 is reserved for documentation. |
| 4200000000 – 4294967294 | Private 32-bit | The 32-bit equivalent of the 64512–65534 private block. |
The tool accepts any value from 1 to 4294967295, so both classic 16-bit numbers like AS3356 and 32-bit numbers like AS200000 resolve normally. If you see AS23456 in an AS path, that is not a real network — it is AS_TRANS standing in for a 32-bit ASN that an intermediate router could not represent.
AS13335, 13335) or an IP address (1.1.1.1, 2606:4700:4700::1111). Mode is detected automatically, and you can override it.Built-in examples get you started fast: Google (AS15169), Cloudflare (AS13335), Amazon AWS (AS16509), and Microsoft (AS8075), plus Google DNS (8.8.8.8) and Cloudflare DNS (1.1.1.1) for the IP-to-AS direction.
Every ASN is issued by one of five regional internet registries, and knowing which one issued a number tells you where the resource was registered — which is not always where the network operates:
| RIR | Full name | Region |
|---|---|---|
| ARIN | American Registry for Internet Numbers | North America |
| RIPE NCC | RIPE Network Coordination Centre | Europe, Middle East, Central Asia |
| APNIC | Asia-Pacific Network Information Centre | Asia Pacific |
| LACNIC | Latin America and Caribbean Network Information Centre | Latin America, Caribbean |
| AFRINIC | African Network Information Centre | Africa |
A mismatch between the registering RIR, the registered country, and where traffic actually appears to originate is a routine signal in abuse investigations — not proof of anything on its own, but worth noting alongside the announced prefix set.
Related network tooling: use whois lookup for domain and registry records, DNS lookup to resolve names to the addresses you then map to an AS, what is my IP to find your own address and upstream AS, and IP risk checker for reputation context on an address you have just attributed.
An autonomous system number is a globally unique identifier for a network that operates a single, coherent routing policy. BGP, the internet’s inter-domain routing protocol, uses ASNs to build AS paths — the list of networks a route has traversed — and to prevent loops.
Switch the tool to IP mode (or just paste an IP — it is detected automatically). It resolves the most specific prefix covering that address in the global routing table and reports the AS originating it, along with that AS’s registry details.
Valid ASNs run from 1 to 4294967295. Values 1–65535 are the original 16-bit space, with 64512–65534 reserved for private use; everything above 65535 is 32-bit space, with 4200000000–4294967294 reserved for private use. AS0 and AS65535 are reserved, and AS23456 is the AS_TRANS placeholder.
All lookups query the RIPEstat data API, which aggregates BGP routing observations and registry (whois) data covering all five RIRs. Results reflect what RIPEstat currently observes in the global routing table.
It is free with no signup. RIPEstat does apply rate limits to its public API, so rapid repeated queries can return a temporary rate-limit message — wait a moment and retry.
The ASN exists as a registered resource but is not currently originating any prefixes visible in BGP. That is normal for newly allocated numbers, for organisations that hold an ASN they have not deployed, and for networks that have been shut down.
Whois answers registry questions — who registered a resource and how to contact them. An AS lookup answers routing questions — what this network actually announces to the internet right now. This tool combines both: registry metadata plus live announced-prefix data.
Yes. Expand the prefixes section to get the full IPv4 and IPv6 announced-prefix lists, and export them as JSON or CSV if you need them in a firewall rule, an allowlist, or an analysis script.
Yes, in both directions. IPv6 addresses resolve to their originating AS, and every AS result reports its IPv6 prefix count and full IPv6 prefix list alongside IPv4.
BGP (Border Gateway Protocol) is the routing protocol that holds the Internet together. It enables autonomous systems (AS) — independently operated networks such as ISPs, cloud providers, enterprises, and content delivery networks — to exchange routing information and establish paths for traffic to flow between them. Every organization with its own IP address space and Internet connectivity is assigned an Autonomous System Number (ASN).
AS lookup retrieves information about an autonomous system: its assigned IP prefixes, peering relationships, geographic presence, and organizational ownership. This data is essential for network engineering, threat intelligence, incident response, and Internet research.
| Field | Description | Example |
|---|---|---|
| ASN | Autonomous System Number | AS13335 |
| Organization | Entity operating the AS | Cloudflare, Inc. |
| Announced Prefixes | IP address blocks routed via this AS | 104.16.0.0/13, 172.64.0.0/13 |
| Upstream Providers | Transit providers carrying traffic | AS174 (Cogent), AS3356 (Lumen) |
| Peers | Networks exchanging traffic directly | AS6939 (Hurricane Electric) |
| IXP Presence | Internet Exchange Points where the AS connects | AMS-IX, DE-CIX, LINX |
| Country | Registration country | United States |
| RIR | Regional Internet Registry (allocating body) | ARIN, RIPE, APNIC |
An Autonomous System (AS) number is a unique identifier assigned to a network or group of networks that operate under a single administrative policy. AS numbers are essential for BGP (Border Gateway Protocol) routing, which allows different networks on the internet to exchange routing information. Large organizations like Google (AS15169), Cloudflare (AS13335), and Amazon AWS (AS16509) each have their own AS numbers.
Use the IP to AS Lookup mode in this tool by entering any valid IPv4 or IPv6 address. The tool will query BGP routing tables to identify the AS that announces the route for that IP, along with the specific prefix (CIDR block) it belongs to. This is useful for identifying the network operator responsible for an IP address or investigating network connectivity.
Regional Internet Registries are organizations that manage the allocation and registration of IP addresses and AS numbers 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). This tool displays which RIR allocated each AS number.
Prefixes are blocks of IP addresses that an AS advertises via BGP to the internet. IPv4 prefixes use the format like 8.8.8.0/24 (announcing 256 addresses), while IPv6 prefixes are longer, like 2001:4860::/32. This tool shows how many IPv4 and IPv6 prefixes each AS announces, giving insight into the size and scope of a network operator.
The tool displays abuse contact email addresses when available for each AS. These contacts are registered with the RIR and should be used to report network abuse, spam, security incidents, or other issues originating from that network. Copy the abuse contact email directly from the results to submit your report.
Yes, you can export AS information in either JSON or CSV format. The export includes the AS number, name, description, country, RIR allocation, prefix counts, and contact information. This is useful for documentation, network analysis reports, or integrating the data into other tools and databases.