# How to find which ISP and ASN an IP address belongs to

> How to find which ISP and ASN an IP address belongs to: whois, the free RIPEstat API and a one-line script. Check any ISP proxy before you rely on it. No KYC.

- URL: https://pinnedip.com/guides/check-ip-isp-asn/
- Last updated: 2026-10-19
- Publisher: PinnedIP (https://pinnedip.com)

The provider name an ISP proxy shows comes from routing and registration data anyone can query. Three free ways to read it, and what the answers mean.

**Quick answer — How do I find the ISP and ASN of an IP address?**

Query the routing data: the free RIPEstat API returns the AS number that announces an IP and the holder’s name, and `whois` returns who registered the block. For example, AT&T’s main network is AS7018. **PinnedIP** shows each IP’s provider at checkout; its US ISP IPs cost $2.03 for 30 days (October 2026).

## What is an ASN, and why does it matter for ISP proxies?

An autonomous system number (ASN) identifies a network that announces blocks of IP addresses to the rest of the internet. Every public IP is announced by at least one AS, and the AS has a registered holder, such as "AT&T Enterprises" for AS7018 or "Comcast Cable Communications" for AS7922.

Websites and IP-type databases use that holder to classify an address as a consumer provider, a business network or a hosting company. An ISP proxy is valuable because its AS holder is a consumer provider; you can verify that yourself in a minute.

## Way 1: the RIPEstat API (any IP, any region)

RIPEstat is run by RIPE NCC and covers the whole internet, not only Europe. Its `network-info` call returns the announcing AS for an IP, and `as-overview` returns the holder name:

*curl: which AS announces this IP, and who holds it?*

```bash
curl -s "https://stat.ripe.net/data/network-info/data.json?resource=203.0.113.10"
curl -s "https://stat.ripe.net/data/as-overview/data.json?resource=AS7018"
```

## Way 2: whois (who registered the block)

`whois` asks the regional registry (ARIN for most US addresses) who registered the block. The answer can name the provider, or a business customer the provider assigned the block to. Run `whois 203.0.113.10` on macOS or Linux, or use ARIN’s web search at search.arin.net. When whois and the routing data disagree, the routing data (Way 1) is what most websites use.

## Way 3: one script for many IPs

If you rent 10 or 100 IPs, check them in one pass. This Node.js script (version 18 or later, no packages) prints the announcing AS and holder for each address in a list:

*Node.js: AS number and holder for a list of IPs*

```javascript
const ips = ['203.0.113.10', '203.0.113.11'];

async function lookup(ip) {
  const net = await (await fetch(`https://stat.ripe.net/data/network-info/data.json?resource=${ip}`)).json();
  const asn = net.data.asns[0];
  if (!asn) return `${ip}\tnot announced`;
  const ov = await (await fetch(`https://stat.ripe.net/data/as-overview/data.json?resource=AS${asn}`)).json();
  return `${ip}\tAS${asn}\t${ov.data.holder}`;
}

(async () => {
  for (const ip of ips) console.log(await lookup(ip));
})();

```

> **Margin note** 203.0.113.0/24 is reserved for documentation (RFC 5737), so the examples return "not announced". Use your own IPs.

## Which AS numbers do the main US providers use?

Our provider pages list them with their IPv4 counts (RIPEstat, October 18, 2026). The main ones: [AT&T](https://pinnedip.com/isps/att/) AS7018, [Comcast](https://pinnedip.com/isps/comcast/) AS7922, [Verizon](https://pinnedip.com/isps/verizon/) AS701, [Spectrum](https://pinnedip.com/isps/spectrum/) AS20115 and regional networks, [Cox](https://pinnedip.com/isps/cox/) AS22773, [Frontier](https://pinnedip.com/isps/frontier/) AS5650, [Lumen (CenturyLink)](https://pinnedip.com/isps/lumen-centurylink/) AS209, [Windstream](https://pinnedip.com/isps/windstream-kinetic/) AS7029 and [Astound (RCN)](https://pinnedip.com/isps/astound-rcn/) AS6079.

## ISP and ASN lookups: FAQ

### Why does a lookup show a hosting company for my proxy?

Then the IP is announced by a hosting network, which makes it a datacenter proxy, not an ISP proxy. See [ISP vs datacenter proxies](https://pinnedip.com/compare/isp-vs-datacenter-proxies/). If a PinnedIP IP shows that, contact support.

### Can one IP show two different providers?

Yes, when a provider was bought and kept its old network. Cox addresses still show AS22773 after Charter bought Cox in August 2026, and Frontier keeps AS5650 under Verizon.

### Is the ASN the same as the city?

No. The ASN tells you the network; the city comes from geolocation databases. See [why ISP IP cities differ](https://pinnedip.com/guides/isp-ip-geolocation/).

## Sources

1. [RIPEstat Data API: network-info](https://stat.ripe.net/docs/data-api/api-endpoints/network-info) — RIPE NCC (2026-10-19)
2. [RIPEstat Data API: as-overview](https://stat.ripe.net/docs/data-api/api-endpoints/as-overview) — RIPE NCC (2026-10-19)
3. [RFC 5737: IPv4 address blocks reserved for documentation](https://www.rfc-editor.org/rfc/rfc5737) — IETF (2026-10-19)

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