RoutingJSON APILive · RIR WHOIS + BGP prefixes

ASN Lookup

Look up the registrant details for any autonomous system, and on request the prefixes it originates in the global routing table. Free. No API key. No API rate limits you’ll ever reasonably hit.

Live Test

Query an ASN

Enter an AS number, with or without the “AS” prefix.

Examples: AS15169 · Google AS13335 · Cloudflare AS3356 · Lumen AS32934 · Meta AS2906 · Netflix

Include originated prefixes

Enter an ASN above and click Lookup to see the response.

Browse

Well-known networks

Every AS in the routing table has its own page at /asn/ and its number: prefixes, RPKI, neighbors, IRR and ASPA.

AS13335 Cloudflare AS15169 Google AS16509 Amazon AS8075 Microsoft AS32934 Meta AS2906 Netflix AS20940 Akamai AS3356 Lumen AS174 Cogent AS1299 Arelion AS2914 NTT AS6939 Hurricane Electric AS7018 AT&T AS7922 Comcast AS3320 Deutsche Telekom

Reference

API Documentation

The parameters and fields for this tool. Keys, errors, CORS and rate limits work the same for every tool: see the API guide.

GET/v1/asn/{number}

Look up an autonomous system. Always returns RIR WHOIS registrant data and per-family prefix counts (IPv4 / IPv6). Pass prefixes=true to also include the prefix lists.

Parameter	Type	Description
asn	string	An AS number, with or without the `AS` prefix (`15169` or `AS15169`).
prefixes	boolean	Set to `true` to include the IPv4 and IPv6 prefix lists this ASN originates. Optional; defaults to `false`.

# WHOIS only (default)
curl -s "https://api.notoolkit.com/v1/asn/15169" | jq .

# include originated prefixes
curl -s "https://api.notoolkit.com/v1/asn/15169?prefixes=true" | jq .

POST/

Identical lookup via JSON body. Add "prefixes": true to include originated prefixes.

# cURL example
curl -s -X POST https://api.notoolkit.com/v1/asn \
  -H 'Content-Type: application/json' \
  -d '{"asn":"15169","prefixes":true}' | jq .

Response Fields

Field	Type	Description
query	string	The normalized ASN you submitted (e.g. `AS15169`).
asn	integer	The autonomous system number.
asn_name	string	Short AS name from the RIR.
org_name	string	Full registered organization name.
country	string	ISO 3166-1 alpha-2 country code of the registrant.
description	string	Free-text description / remarks from the RIR record.
rir	string	Registry holding the ASN: `ARIN`, `RIPE`, `APNIC`, `LACNIC`, or `AFRINIC`.
whois_raw	string	First 4 KB of the raw WHOIS response for the ASN.
prefix_count	object	Prefix counts originated by this ASN, split by family: `{ "ipv4": int, "ipv6": int }`. Always present.
prefixes	object	Originated prefixes split by family: `{ "ipv4": [...], "ipv6": [...] }` (each list capped at 1000; see `prefix_count` for the true totals). Only present when `prefixes=true`.
aspa	object	This AS’s ASPA: `{ "published": bool, "providers": [...], "ta": string, "customer_count": int }`, where `customer_count` is how many ASes name it as a provider. `null` when ASPA data is unavailable.
cache_hit	boolean	`true` if the WHOIS data was served from the Redis cache (14-day TTL).

Error Responses

HTTP	Meaning
`400`	Missing or invalid `asn` parameter.
`404`	No routing-table or WHOIS data found for the ASN.
`503`	Database temporarily unavailable.

FAQ

Common Questions

What does the ASN lookup return?

Always the RIR WHOIS registrant data for the AS (name, organization, country, registry), the same data the IP→ASN tool shows, plus per-family prefix counts (IPv4 and IPv6). Opt in with prefixes=true (or the checkbox above) to also get the prefix lists themselves, split into IPv4 and IPv6 and sourced from the RouteViews BGP table.

Where do the announced prefixes come from?

From the same RouteViews BGP table that powers the IP→ASN tool, imported every 4 hours. The list reflects what the AS is originating as of the most recent import.

Why is a prefix_count sometimes 0?

An ASN can be registered with a RIR but not currently originate any prefixes of a given family in the global table (for example a transit-only AS, or one that announces IPv4 but no IPv6). In that case the relevant count is 0, and if you requested prefixes the matching list is empty. You still get the WHOIS data.