ASN lookup
The organisation behind an autonomous system number, and the networks that use it.
Registry data from RDAP; the description and routing data from Team Cymru’s public DNS service. Both are queried straight from your browser.
Preguntas frecuentes
What is an autonomous system?
A network that decides for itself how traffic reaches it, and announces that to the rest of the internet with BGP. Every ISP is one, as is every large hosting provider and many big companies and universities. The AS number is its identifier.
How do I find the ASN for a website?
Look up the site’s address first with the DNS lookup, then paste that address here. This tool accepts an address directly and will find the AS announcing it for you.
Why do some AS numbers look much larger than others?
The original scheme used 16-bit numbers, up to 65535, and those were handed out first — so a low number usually means an old network. The space was extended to 32 bits in 2007, which is why newer networks have numbers in the hundreds of thousands.