What is an ASN?
An Autonomous System Number (ASN) is a unique identifier assigned to a collection of IP address blocks that share a single, clearly defined routing policy on the public internet.
The internet is not one network — it is tens of thousands of independently operated networks, each called an Autonomous System (AS). Your home ISP is an AS. Google is an AS. Cloudflare is an AS. Each AS gets a globally unique ASN.
How the Internet Uses ASNs
Autonomous Systems exchange routing information using the Border Gateway Protocol (BGP). Each AS announces which IP address prefixes it controls and which other ASes it can reach them through. This is how traffic knows how to get from your device to a server on the other side of the world.
The path a packet takes across the internet is recorded as an AS_PATH — a sequence of ASNs the announcement has passed through. For example:
3462 (Chunghwa Telecom) → 6453 (Tata Communications) → 15169 (Google)
When something breaks on the internet, BGP engineers often talk about AS paths, route leaks and prefix hijacks — all of which involve ASNs.
Who Gets an ASN?
ASNs are assigned by Regional Internet Registries (RIRs):
- ARIN — North America
- RIPE NCC — Europe, Middle East, Central Asia
- APNIC — Asia-Pacific
- LACNIC — Latin America and Caribbean
- AFRINIC — Africa
Originally ASNs were 16-bit numbers (1–65535). As demand grew, 32-bit ASNs were introduced, allowing over four billion unique values. Private ASNs (64512–65534 in the 16-bit range) are used inside organisations without needing global uniqueness — similar to how 192.168.x.x is used for private IPv4.
What Your ASN Reveals
When a website or API looks up your IP address, the ASN provides immediate context about what kind of connection you are using:
| ASN type | What it signals |
|---|---|
| Residential ISP | Normal consumer connection. Chunghwa Telecom, Comcast, BT etc. |
| Cloud / Hosting provider | AWS, Google Cloud, DigitalOcean — likely a server, bot or VPN exit node |
| VPN provider | Mullvad, NordVPN, ExpressVPN — user is masking their real IP |
| Mobile carrier | Shared NAT IP from a carrier-grade network. Geolocation is unreliable. |
| Corporate proxy | Traffic routes through a business network before reaching the internet |
| Tor exit node | Anonymised traffic from the Tor network |
This is why streaming services, banks and fraud detection systems check ASN. A login from a residential ISP in Taiwan and a login from a data center in a different country might indicate account sharing or credential stuffing — even if the IP geolocation shows the same country.
ASN and IP Geolocation Accuracy
IP geolocation databases map IP address ranges to geographic locations. The accuracy of this mapping depends heavily on the ASN type:
- Residential ISPs: Usually accurate to city level. The ARIN/RIPE registration record often includes a region.
- Mobile carriers: Often inaccurate. Mobile networks use carrier-grade NAT and assign IPs based on the carrier's network hub, not your physical location.
- VPNs: Shows the location of the VPN server exit node, not you.
- CDNs and cloud providers: May show a data center location in a completely different region.
How to Look Up an ASN
The IP tool on this site shows your current ASN and organization name directly from Cloudflare's edge metadata — no third-party database required. You can also query the raw JSON:
curl https://gatecko.com/api/ip
The response includes an asn field (the numeric ASN) and an asOrganization field (the network operator name).