Learn what an ASN is, how to look up which network and ISP an IP address belongs to, and how accurate IP geolocation really is.
Every public IP address belongs to a network, and every network on the internet has a number. Knowing which network an IP belongs to tells you who operates it, who to contact about abuse, and roughly where it is.
The internet is a network of networks. Each independently routed network — an ISP, a cloud provider, a university, a large company — is an autonomous system and gets an ASN (autonomous system number), such as AS13335 for Cloudflare or AS15169 for Google. Autonomous systems announce which IP ranges they route using BGP, which is how the rest of the internet knows where to send traffic.
Enter an IP address or hostname in the IP lookup. You get:
Leave the field empty and it shows your own public IP address and network — useful for checking whether a VPN is working or whether you are behind CGNAT.
Country is right in the vast majority of cases. City is an educated guess based on registration data and measurements, and is often off by tens or hundreds of kilometres — mobile networks and large ISPs frequently map whole regions to one city. Anycast addresses, such as those of big CDNs and public DNS resolvers, are served from many locations at once, so any single location for them is misleading.
AS13335, as well as from countries and cities.The lookup is also available through the JSON API and in Telegram: send /info 1.1.1.1 to the check-host.one bot.