Turn an AS number into the network name, registry and allocation date
Runs in your browser. Only the lookup you start is sent to cloudflare-dns.com or dns.google; nothing else leaves your device. Updated on 25 Oct 2026.An AS number such as AS13335 turns up in traceroutes, firewall logs and BGP tools with no name attached. Type it, with or without the AS prefix, and the page returns the organisation it is registered to, the regional registry that assigned it, the country and the date.
Type the number, such as AS13335, in AS number (or an IP address); the AS prefix is optional.
Press Look up, or press Try an example to see AS13335 answered.
Read the Network name, Country, Registry and Allocated date for that number.
Press Copy result to copy the owner details.
Numbers from 64512 to 65534 are reserved for private use, so they have no public owner.
The internet is made of tens of thousands of autonomous systems: networks such as an ISP, a cloud provider or a university, each with its own AS number, that tell each other which address blocks they carry using BGP. This ASN lookup takes an IP address and tells you which of them announces it, or takes an AS number and tells you who it belongs to.
For an IP, the page shows the origin AS, the BGP prefix that covers the address, the country and regional registry (ARIN, RIPE NCC, APNIC, LACNIC or AFRINIC) and the allocation date, then the AS's registered name. When more than one prefix covers the address, the most specific one is listed first, because that is the route traffic follows. When two networks announce the same prefix, the page says so: that can be deliberate, or a sign of a route leak.
The answers come from Team Cymru's IP to ASN mapping service, which publishes this routing data as DNS TXT records. For 8.8.8.8 the page asks for the TXT record at 8.8.8.8.origin.asn.cymru.com and gets back "15169 | 8.8.8.0/24 | US | arin | 2023-12-28", then asks AS15169.asn.cymru.com for the name. Both questions go through the public resolver you choose, Cloudflare or Google, so the IP or AS number you type is sent to that resolver and, through it, to Team Cymru's servers; nothing else leaves your device.
The rest of the article, and all 6 questions about ASN Lookup, are on the ASN Lookup page.
An autonomous system number identifies one network on the internet, such as an ISP, a cloud provider or a large company, that announces its own blocks of addresses to other networks using BGP. Google is AS15169 and Cloudflare is AS13335. Regional registries such as ARIN and RIPE NCC assign the numbers.
Type the IP address. The page asks Team Cymru's routing data which AS announces it, then asks for that AS's registered name. The answer shows the AS number, the organisation, the BGP prefix covering the address, the registry and the country it was allocated in.
The IP address, reversed into a DNS name, or the AS number goes to the resolver you choose, Cloudflare or Google, which forwards the question to Team Cymru's name servers. Nothing else leaves your device, and private addresses such as 192.168.1.1 are answered on the page without any request.
Only roughly. The country shown is where the address block was registered, which for a cloud or mobile network is often a different country from the device using it. An ASN lookup names the network, never a street address or the person behind a connection.
Still stuck? Ask about ASN Lookup and anybody who knows can answer. No account needed.
Same job, other tools: CNAME Lookup – Check where a CNAME alias points and follow the chain to its final address · NS Lookup – Find the name servers a domain is delegated to, and how long resolvers cache them · DNSKEY Lookup – List a zone’s DNSKEY records with key tags, KSK or ZSK roles, algorithms and key sizes · DS Record Lookup – Read the DS record the parent zone holds and see whether it matches a published key.
On the related tools: Open Port Checker – See if a port forwarded on your router is reachable from the internet.