ASN Lookup
Look up an Autonomous System (RDAP).
Enter a value above to run ASN Lookup
e.g. AS13335
Quick answer
ASN Lookup returns details about an Autonomous System via RDAP: the organization that operates it, its country, and registration data. An ASN identifies a network operator (such as an ISP or hosting provider) that announces IP routes on the internet.
An Autonomous System Number (ASN) identifies a network that controls its own IP address blocks and routing policy on the internet, such as an ISP, hosting provider, or large enterprise. This tool queries RDAP (Registration Data Access Protocol) at the responsible Regional Internet Registry to return the registered details behind an ASN. Use it to confirm who operates a network, find abuse and technical contacts, check registration and last-changed dates, and see which registry manages the number.
How it works
You enter an AS number (for example AS15169 or just 15169). The tool sends an RDAP autnum request, which resolves through IANA's bootstrap data to the correct registry: ARIN, RIPE NCC, APNIC, LACNIC, or AFRINIC. RDAP is the modern JSON-based successor to WHOIS, so responses are structured and machine-readable. The registry returns the AS name, the organization holding it, contact entities, and registration events rather than plain free-form text.
How to read the results
The handle and name identify the ASN and its short label. The entities block lists the organization plus roles like registrant, administrative, technical, and abuse, often with email addresses worth saving for reports. Events show when the record was registered and last changed. Status flags and the registry (port43 or rdapConformance hints) tell you which RIR is authoritative. Remoteroutable prefixes are not part of autnum data; use a route or BGP tool for those.
Why it matters
When traffic, spam, or an attack traces back to an IP, mapping that IP to its ASN tells you which network is actually responsible, which is essential for filing an accurate abuse report or blocklist decision. Researchers use ASNs to group ranges by operator, verify peering relationships, and audit which provider hosts a service. Knowing the owning organization behind a number removes guesswork when a plain IP address is ambiguous.
Frequently asked questions
- What is the difference between an ASN and an IP address?
- An IP address identifies a single host or interface. An ASN identifies an entire network under one administrative and routing policy that may announce thousands of IP prefixes. One ASN can cover many IP ranges. You map an IP to its ASN to learn which operator controls that address on the global routing table.
- Why does an ASN lookup return no contact email?
- Some registries redact personal data under privacy rules, or the operator only publishes an abuse role without a public technical email. RIPE and AFRINIC sometimes mask fields. If no address appears, check the linked organization entity, the abuse contact object, or query the registry's website directly for a current reporting address.
- How do I find the ASN for a given IP address?
- This tool queries an ASN directly, so you first need the AS number. Run an IP or RDAP lookup on the address to find its origin AS, then paste that number here for full registration details. Many BGP and routing tools also show the origin ASN that announces the prefix containing your IP.