Can this tell me someone's location?

No, and tools that claim to are mostly guessing. What is published is which network announces the address and which registry allocated the block. Street-level claims come from commercial databases built on inference, and they are wrong often enough to matter.

The block of addresses announced as one unit, written like 1.0.0.0/24. The number after the slash is how many bits are fixed, so a /24 is 256 addresses and a /16 is 65,536.

Why do two addresses from the same company show different AS numbers?

Large companies run several networks, and may announce different blocks from different ones. Cloud providers in particular have many, often one or more per region.

How do I find the address behind a domain?

Use the DNS Lookup tool and read the A record, which is the IPv4 address, or AAAA for IPv6. Then bring the address back here.

IP Address Lookup

Takes an address out of a log file and says which network it belongs to, which registry allocated it and what name it claims. Useful when deciding whether traffic is a cloud provider, a home connection or something else.

The address you type is sent to Cloudflare or Google's public resolver, and through it to Team Cymru, who publish the internet's routing table as DNS. Nothing is stored here.

How to use IP Address Lookup

1Paste an IPv4 or IPv6 address.
2Press look up.
3Read the network, the AS number and the announced prefix.
4Check the reverse name for a second opinion about what the address is.

What an AS number tells you

The internet is a few thousand networks that announce which address ranges they carry. Each is an autonomous system with a number, and the announcement is public: AS13335 is Cloudflare, AS15169 is Google, AS16509 is Amazon.

Knowing which one announces an address is usually enough to answer the real question. Traffic from a hosting provider's range behaves differently from traffic on a residential ISP, and a scraper pretending to be a browser is often given away by sitting in a data centre range.

Where the answer comes from

Team Cymru publish the routing table as DNS records, so asking which network announces an address is an ordinary TXT query. That is what makes this work in a browser at all, with no account, no key and no third service to explain.

The prefix shown is the block actually announced, which is often larger than you would guess: a single address usually sits inside a /24 or a /20 that moves as one.

Addresses with no owner to find

Private ranges such as 10.0.0.0/8 and 192.168.0.0/16 are not announced anywhere, because they mean something different on every network. An address from one tells you nothing about who it belongs to beyond the network it was seen on, and the page says so rather than returning an empty result.

Limits

No geolocation beyond the country the network is registered in, which is often where the company is rather than where the address is used.
Private, loopback and reserved ranges have no owner to look up.
The registry allocation date is when the block was allocated, not when its current user took it on.
An address behind a proxy or a VPN describes the proxy, not whoever is using it.

Frequently asked questions

Can this tell me someone's location?: No, and tools that claim to are mostly guessing. What is published is which network announces the address and which registry allocated the block. Street-level claims come from commercial databases built on inference, and they are wrong often enough to matter.
What is a prefix?: The block of addresses announced as one unit, written like 1.0.0.0/24. The number after the slash is how many bits are fixed, so a /24 is 256 addresses and a /16 is 65,536.
Why do two addresses from the same company show different AS numbers?: Large companies run several networks, and may announce different blocks from different ones. Cloud providers in particular have many, often one or more per region.
How do I find the address behind a domain?: Use the DNS Lookup tool and read the A record, which is the IPv4 address, or AAAA for IPv6. Then bring the address back here.