ASN Lookup
AvailableUse this tool to determine which company owns the specified Autonomous System Number (ASN), with registry, country and allocation details.
Look up an AS number
Enter an AS number to see which organization holds it.
How it works
The NetTools server finds the regional internet registry responsible for the number in the IANA RDAP bootstrap registry (ARIN, RIPE NCC, APNIC, LACNIC or AFRINIC), then reads its public autnum record. Private-use, documentation and reserved numbers are explained without a lookup.
Safeguards & responsible use
- Queries go only to RDAP servers listed by IANA, over HTTPS — never to user-supplied hosts.
- Only the holder organization is shown; names of individual contacts in registry records are not displayed.
- Rate limited, time limited and response-size limited.
Frequently asked questions
What is an ASN?
An Autonomous System Number identifies a network that has its own routing policy on the internet — typically an ISP, cloud provider, content network or large enterprise. Networks exchange routes with each other using BGP and their AS numbers.
Why does my ASN show no owner?
Numbers in private-use ranges (64512–65534, 4200000000–4294967294) and documentation ranges are never registered to anyone. Unallocated numbers have no registry record at all.
What is the difference between 2-byte and 4-byte ASNs?
Original AS numbers were 16-bit (up to 65535). Since RFC 6793, 32-bit numbers up to 4,294,967,295 are assigned too; they are sometimes written in asdot form, e.g. 1.10 for 65546.