ASN WHOIS Lookup — Find the Owner of Any AS Number

Retrieve the registered owner, network name, org handle, and address for any Autonomous System Number via live RDAP and WHOIS data.

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ASN WHOIS Lookup — Find the Registered Owner of Any Autonomous System

ASN WHOIS lookup queries the Regional Internet Registry (RIR) database via RDAP (RFC 7480) or legacy WHOIS (port 43, RFC 3912) to return the registered organization, network name, and registry handle for any Autonomous System Number. An ASN is a globally unique 16-bit or 32-bit identifier assigned by IANA and delegated to one of five RIRs — ARIN, RIPE NCC, APNIC, LACNIC, or AFRINIC — to identify a network that participates in BGP routing on the public internet.

Fact	Detail
Primary protocol	RDAP (RFC 7480) via rdap.org/autnum/
Fallback protocol	Port 43 WHOIS at whois.iana.org (RFC 3912)
Data source	ARIN, RIPE NCC, APNIC, LACNIC, AFRINIC
Accepted input formats	AS15169 or bare number 13335
16-bit ASN range	0–65,535 — private use reserved: 64,512–65,534 (RFC 6996)
32-bit ASN range	0–4,294,967,295 — private use reserved: 4,200,000,000–4,294,967,294 (RFC 6996)

How to Look Up ASN WHOIS Registration Data

Results are returned directly from RDAP (RFC 7480) with no caching delay.

Enter an ASN

Enter an Autonomous System Number in the field above using the format AS15169 or a bare number such as 13335. Both formats are accepted.

Submit the Lookup

Click "Lookup ASN WHOIS" to query the RIR RDAP database at rdap.org/autnum/ in real time.

Review Organization and Network Details

The result shows the registered organization name, network name (AS handle), and registry org ID assigned to the ASN.

Inspect the Raw RDAP Record

Expand the Registry Routing Record panel to view or copy the full RDAP JSON response directly from the RIR — no reformatting applied.

What the ASN WHOIS Results Mean

Field	What It Means	Example
ASN	The Autonomous System Number in AS-prefixed format, normalized from your input	AS15169
Network Name	Short identifier for the AS registered at the RIR — the AS handle	GOOGLE
Legal Name	Full legal name of the organization that controls the AS, from the RDAP entity vCard	Google LLC
Handle / Org ID	Registry-assigned identifier for the organization record at the RIR	GOGL
HQ Address	Mailing address on file with the RIR — may be a legal address, not operational location	1600 Amphitheatre Pkwy, Mountain View, CA, US
Registry Routing Record	Full RDAP JSON response from the RIR — the raw autnum object with all entities	JSON object, copy-ready

How ASN WHOIS Lookup Works — Technical Details

The tool sends an HTTPS GET request to rdap.org/autnum/{asn}. The rdap.org proxy routes the query to the authoritative RIR RDAP endpoint — ARIN for North American ASNs, RIPE NCC for European and Middle Eastern ASNs, APNIC for Asia-Pacific, LACNIC for Latin America, and AFRINIC for Africa — and returns a structured JSON response conforming to RFC 9083 (RDAP JSON responses).

If the RDAP endpoint returns an error or is unreachable, the tool falls back to a port 43 WHOIS query at whois.iana.org using the AS{number} query format. IANA's WHOIS server redirects to the appropriate RIR's port 43 server via the IANA whois referral mechanism. The raw WHOIS text is returned as-is in the Registry Routing Record panel.

ASN numbers exist in two formats per RFC 5396: 2-byte (16-bit, AS0–AS65535, introduced with BGP-4) and 4-byte (32-bit, AS0–AS4294967295, standardized in 2007 per RFC 4893 to address exhaustion of the 65,536-ASN pool). Private-use ASNs are reserved per RFC 6996: 64512–65534 for 16-bit and 4200000000–4294967294 for 32-bit. Private ASNs are not announced on the public internet and will return no RIR RDAP record.

Command line

How to Look Up ASN WHOIS Without an Online Tool

The whois command performs ASN WHOIS lookups natively on Linux and macOS. Note that nslookup and dig are DNS tools — they do not query WHOIS or RDAP databases and cannot be used for ASN lookups.

Mac / Linux whois

whois AS15169

The system whois client routes automatically to the correct RIR. To query a specific RIR's port 43 server directly:

whois -h whois.arin.net AS15169       # ARIN — North America
whois -h whois.ripe.net AS3333        # RIPE NCC — Europe, Middle East
whois -h whois.apnic.net AS4608       # APNIC — Asia-Pacific
whois -h whois.lacnic.net AS28573     # LACNIC — Latin America
whois -h whois.afrinic.net AS37153    # AFRINIC — Africa

Windows PowerShell (RDAP — no install required)

Invoke-RestMethod "https://rdap.org/autnum/15169" | ConvertTo-Json -Depth 10

Returns the same structured RDAP JSON that the online tool displays. Pipe to Out-File asn15169.json to save the result locally.

Windows Command Prompt with Sysinternals whois.exe

Windows has no built-in whois command. Download whois.exe from the Microsoft Sysinternals suite, then:

whois AS15169

The online tool queries via RDAP at rdap.org/autnum/ — results may differ from a local whois client if registration data has changed since your client last resolved the RIR endpoint.

Common Uses for ASN WHOIS Lookup

A security analyst receives alerts showing repeated unauthorized access attempts from multiple IP addresses. Routing all source IPs through IP to ASN Lookup reveals they originate from a single ASN. ASN WHOIS Lookup returns the registered organization and abuse contact, letting the analyst file a structured abuse report with the NOC rather than reporting individual IPs one at a time.

A network engineer preparing to establish a BGP peering session with an upstream provider needs to confirm the organization behind the remote ASN before adding it to the router configuration. ASN WHOIS Lookup confirms the legal entity, registry handle, and RIR of record, verifying the AS is operated by the expected organization before any routing policy is applied.

A threat intelligence analyst tracking a botnet campaign identifies multiple C2 servers across different IP addresses. IP to ASN Lookup maps all of them to the same two ASNs. ASN WHOIS Lookup identifies both as bulletproof hosting providers with a history of ignoring abuse reports, enabling the analyst to build blocklists at the ASN level rather than chasing individual IPs.

Frequently Asked Questions

What is an Autonomous System Number (ASN)?

An Autonomous System Number (ASN) is a globally unique 16-bit or 32-bit integer assigned by IANA and delegated through one of five Regional Internet Registries (ARIN, RIPE NCC, APNIC, LACNIC, AFRINIC) to a network operator, ISP, or large enterprise. The ASN identifies the organization responsible for routing a group of IP prefixes on the public internet using the Border Gateway Protocol (BGP). Well-known examples include AS15169 (Google), AS13335 (Cloudflare), and AS16509 (Amazon AWS).

What is the difference between ASN WHOIS and a BGP lookup?

ASN WHOIS retrieves the registration record for an ASN from the RIR database — the organization name, contact information, and registry handle. BGP lookup retrieves routing data — the IP prefixes the ASN is currently announcing and the AS path through the internet. WHOIS answers "who registered this AS." BGP answers "what networks is this AS advertising right now." Both query entirely different data sources: WHOIS queries RIR databases via RDAP or port 43; BGP queries route collectors such as RIPE Stat or bgp.he.net.

How accurate is ASN WHOIS data?

ASN ownership registration data is authoritative — RIR records are exact by design because the global routing infrastructure depends on them. The tool queries live RDAP data from rdap.org/autnum/ with no caching delay. Organization name, address, and contact fields may be outdated if the registrant has not updated their RIR record. The AS name (short identifier) is occasionally abbreviated or non-descriptive of the actual organization.

How do I find the ASN for an IP address?

Use the IP to ASN Lookup tool — enter any IPv4 or IPv6 address and the tool returns the originating ASN and the announced CIDR block. ASN WHOIS Lookup accepts only AS numbers as input; it does not resolve IPs to ASNs. To investigate an IP fully: start with IP to ASN Lookup to find the ASN, then run ASN WHOIS Lookup to retrieve the full registry record for that autonomous system.

Do you log or store the ASNs I look up?

ASN lookup queries are not logged or stored. The tool queries rdap.org/autnum/ in real time and returns the result directly to your browser. No lookup history is retained on our servers.

What does RDAP mean and why does the tool use it instead of WHOIS?

RDAP (Registration Data Access Protocol, RFC 7480) is the IETF-standardized successor to legacy WHOIS (port 43, RFC 3912). RDAP returns structured JSON over HTTPS, supports access control, and produces consistent output across all five RIRs. The tool uses RDAP as the primary query method via rdap.org/autnum/ and falls back to port 43 WHOIS at whois.iana.org only when RDAP is unavailable for that ASN.

Related Guides

Guide What Is an IP Address?

background on the IP addressing system that ASNs manage at the routing level via BGP.

Guide What Is IPv4?

understanding IPv4 addressing and the CIDR blocks that autonomous systems announce to the internet.