How to Look Up Any IP Address (Geolocation, ISP)

Your server logs show 3,000 failed logins in an hour, all from 203.0.113.42. Who is that? A botnet, a cloud server or your colleague who forgot their password again? An IP lookup won’t name names, but it will tell you roughly where an address is and whose network it belongs to.

What is an IP address?

An IP (Internet Protocol) address is a number that identifies a device or network interface on a network and tells routers where to deliver data. Every time you load a website, send an email or stream a video, IP addresses route the traffic between your device and the server.

A lookup returns what's publicly known about an address: its approximate location and the network or company that runs it. That comes in handy for security work, network admin and debugging connections.

Public and private IP addresses

Private addresses are used inside local networks, such as your home Wi-Fi, and never travel across the public internet. Your router gives each device a private address, and they all share one public address from your ISP. Websites only ever see that public one.

Reserved IPv4 ranges

# Private ranges (RFC 1918)
10.0.0.0    - 10.255.255.255   (10.0.0.0/8)
172.16.0.0  - 172.31.255.255   (172.16.0.0/12)
192.168.0.0 - 192.168.255.255  (192.168.0.0/16)

# Loopback (localhost)
127.0.0.0   - 127.255.255.255  (127.0.0.0/8)

# Link-local (self-assigned when DHCP fails)
169.254.0.0 - 169.254.255.255  (169.254.0.0/16)

Private addresses can't be geolocated, because the same ranges are reused on millions of separate networks. Somewhere right now, thousands of office printers all have the address 192.168.1.20. A lookup only makes sense for public addresses.

IPv4 and IPv6

IPv4 addresses are 32-bit numbers written as four decimal octets, such as 203.0.113.42. That allows about 4.3 billion addresses, which sounded like plenty in the 1980s. The free pool has since run out.

IPv6 fixes this with 128-bit addresses, written as eight groups of four hexadecimal digits separated by colons. That gives about 3.4 × 10³⁸ addresses. Leading zeros in a group can be dropped, and one run of all-zero groups can be shortened to ::.

Text

# IPv4
203.0.113.42

# IPv6 (full)
2001:0db8:85a3:0000:0000:8a2e:0370:7334

# IPv6 (shortened)
2001:db8:85a3::8a2e:370:7334

# IPv6 loopback
::1

Both versions can be looked up for location and network data.

How IP geolocation works

Geolocation maps an address to a physical place. Providers build databases that link address ranges to countries, regions and cities, using Regional Internet Registry (RIR) records, data from ISPs and inferences from network routing.

Country-level results are usually right. City-level results are much shakier and can be off by tens of kilometres, especially for mobile networks, VPNs and corporate gateways. If the map says your visitor is in a field in the middle of the country, that may just be the database's default point for that country. Treat the coordinates as the rough location of a network, never of a person or a street address.

Common uses for an IP lookup

Security and fraud checks

Fraud systems compare a login or payment IP with what they expect. A customer who always signs in from Lisbon suddenly logging in from a data centre in another country is worth a second look.

Analytics and localization

Analytics tools group visitors by country and region, which informs decisions about translation, ad targeting and new markets. Online shops use it to suggest a currency and shipping options.

Network troubleshooting

When an address shows up in your logs or a traceroute, a lookup tells you whether it belongs to a CDN, a cloud provider or an end-user ISP. That context helps when you track down latency, routing problems or DNS mistakes.

How to use the IP lookup tool

Open the IP address lookup.
Select What’s my IP? to see your own public address, or type any IPv4 or IPv6 address and select Look up (or press Enter).
Read the results: city, region, country, coordinates, organization, timezone and postal code, when the data has them. The organization field starts with the network’s ASN (autonomous system number, the ID every large network gets), for example AS15169 Google LLC.
Select Copy JSON to copy the full result, for example to paste into a ticket or a log note.

The data comes from ipinfo.io, so your browser sends the address you look up to that service. Private and reserved addresses come back without location details.

How to look up any IP address (geolocation and network)