ASN lookup
Look up an autonomous system by AS number, or check which AS announces an IP address.
Queries are proxied through our server and never stored.
How to look up an ASN
- Choose what to look up. Enter an AS number (e.g. AS13335) or an IP address.
- Run the lookup. We query public routing data for the network details.
- Review. See the network name, country, registry and announced prefixes.
The unit of internet routing
The internet isn't one network — it's tens of thousands of independently-run networks stitched together, and each one is an Autonomous System identified by a number. ASNs are what the Border Gateway Protocol (BGP) actually speaks: routers don't reason about individual IPs between providers, they reason about which AS announces a block of addresses and which neighbouring AS to hand traffic to. Numbers were originally 16-bit (0–65535) but ran short, so 32-bit ASNs are now normal; a reserved private range (64512–65534, and a larger 32-bit block) is used inside organisations and never appears on the public internet.
What a lookup reveals
Querying an ASN tells you who operates the network: the organisation name, the Regional Internet Registry it's registered with (ARIN, RIPE, APNIC and so on) and the country, plus the set of IP prefixes the AS announces — which is a rough measure of its size and reach. That's the data behind a lot of practical work: filing an abuse report to the right network, researching peering and transit relationships, or attributing a suspicious IP to a hosting provider versus a residential ISP versus a cloud platform.
From an IP to its network
An IP address and an ASN are two zoom levels of the same question — "where does this traffic live?" The usual flow is to start from an address with the IP address lookup to learn its geolocation and owning AS, then come here to drill into that network's registration and announced ranges. The query is proxied through our server and not stored.
Frequently asked questions
- An Autonomous System Number identifies a network that announces its own routes on the internet — typically an ISP, hosting provider or large organization. Example: AS13335 is Cloudflare.
- Enter an AS number to see its name, country, registry and prefix counts, or enter an IP address to find which AS announces it.
- From the public BGPView API, which aggregates routing and registry data. We proxy the request through our server so nothing about your query is stored.
- Prefixes are the IP address blocks an AS announces to the global routing table. The count gives a rough sense of the network’s size.
- IP lookup focuses on geolocation; ASN lookup focuses on the network and its routing. They complement each other.
- Your ASN is the network your ISP routes you through. Find your public IP with the what-is-my-ip tool, paste that IP address above, and this ASN lookup returns the AS number that announces it.