ASN Lookup
Enter any public IP address to find its ASN — the autonomous system number identifying the network that announces it — plus the organization, ISP, and country behind it.
What is an ASN?
The internet is a network of roughly 100,000 independently operated networks called
autonomous systems — ISPs, cloud providers, universities, large companies.
Each one is identified by an autonomous system number (ASN), such as
AS15169 for Google. Routers use ASNs with the BGP protocol to decide how traffic
travels between networks. A public IP belongs to an address block that is usually originated by
a single AS, but this is not a strict rule: with anycast the same block is announced from many
locations, and multi-origin AS (MOAS) routing means a prefix can legitimately be announced by
more than one AS at the same time.
What an ASN lookup tells you
- Who operates an IP's network: the ASN is usually registered to the network operator that routes the address, which is often more reliable than geolocation — though address blocks can be leased or resold, so the ASN holder isn't always the end user's direct provider.
- Hosting vs residential: an IP announced by a cloud or hosting ASN (AWS, OVH, Hetzner…) usually belongs to a server or datacenter rather than a home connection — a useful hint for spotting bots and VPN exits, though some providers also resell residential or business access.
- Abuse reporting: the AS operator is the right contact for reporting attacks or spam from an address.
How to find your own ASN
Your ASN is the one your ISP announces for the address block your connection sits in. Check your public IP first, then paste it into the box above — the result is your provider's autonomous system. On a mobile connection you will usually see the carrier's ASN; on a VPN you will see the VPN provider's hosting ASN instead of your ISP, which is exactly why the VPN test uses this signal.
ASN lookup vs WHOIS
They answer different questions and people often reach for the wrong one:
| ASN lookup | Given an IP, which autonomous system currently announces it in the global routing table, and who operates that AS. This is routing data — it reflects how traffic is actually being delivered right now. |
| IP WHOIS | Which organization the address block is registered to at a regional internet registry (RIPE NCC, ARIN, APNIC, LACNIC, AFRINIC), plus abuse contacts. Registration and routing can differ when blocks are leased or sub-allocated. |
| AS WHOIS | The registry record for an AS number itself: the holder's name, country, and contacts. |
If an IP looks like it belongs to one company by WHOIS but is announced by another AS, that is not necessarily suspicious — leased address space and cloud hosting produce this constantly.
Finding the ASN of a company by name
There is no single authoritative name-to-ASN directory, because each regional registry maintains its own database and companies often hold several AS numbers across regions. The practical approach is the reverse of a name search: resolve a hostname the organization operates to an IP, then look that IP up here. For a domain, resolve it first (the website IPv6 test shows the addresses a domain publishes), then query one of those addresses.
Reading the result
| ASN | The autonomous system number, written as AS followed by the
number. Numbers up to 65535 are the original 16-bit space; anything larger is a 32-bit ASN
(RFC 6793), which is normal for networks registered in the last decade. |
| Organization | The entity that holds the AS. For consumer connections this is your ISP; for servers it is usually a hosting company. |
| ISP | Often the same as the organization, but can differ when a provider resells capacity from a larger network. |
| Country | The registration country of the AS, which is not always where the specific address is physically used — a global network announces one AS from many countries. |
Looking up an ASN from the command line
whois -h whois.cymru.com " -v 8.8.8.8" — returns the ASN, prefix, and AS name in
one line.
whois AS15169 — the registry record for an AS number.
dig +short AS15169.asn.cymru.com TXT — a DNS-based lookup that works anywhere
dig does.
traceroute 8.8.8.8 — shows the path across networks; combining each hop with an ASN
lookup reveals which operators your traffic crosses.
Related tools
Run a full IP lookup for location and timezone, check the reverse DNS (PTR) record of the same address, or find your own IP to look up first.