What Is an IP Address?
Updated 15 April 2026
A plain-English guide to IP addresses — how IPv4 and IPv6 work, what public vs private means, how DHCP assigns them, and how to look up any IP address.
The basics
Every device connected to a network — your phone, laptop, a web server, a smart TV — has an IP address. IP stands for Internet Protocol. The address is how devices find each other and exchange data, the same way a postal address tells the delivery driver where to drop a package.
When you type a URL into your browser, your computer sends a request to a server. That request carries your IP address so the server knows where to send the response back to.
IPv4 — the original
The most common format is IPv4, written as four numbers separated by dots: 192.168.1.1. Each number is between 0 and 255, giving about 4.3 billion possible addresses.
That sounds like a lot, but with billions of devices online that pool ran out. Network tricks like NAT (Network Address Translation) stretched IPv4 further, but the long-term fix is IPv6.
IPv6 — the future
IPv6 uses 128-bit addresses written in hexadecimal, separated by colons: 2001:0db8:85a3::8a2e:0370:7334. It supports 340 undecillion addresses — enough to give every atom on Earth its own address, several times over.
IPv6 adoption has been gradual, but most modern ISPs and devices support it. Many devices now have both an IPv4 and an IPv6 address simultaneously (called dual-stack).
Public vs private IP addresses
| Type | Assigned by | Visible on internet? | Example ranges |
|---|---|---|---|
| Public | Your ISP | Yes | Any address not in the private ranges |
| Private | Your router (DHCP) | No | 10.x.x.x · 172.16–31.x.x · 192.168.x.x |
Your home has one public IP (shared by all your devices) and each device has a private IP inside the network. When a device sends a request to the internet, your router swaps the private IP for your public IP — that's NAT.
How IP addresses are assigned
Most home and office devices get their IP automatically from a DHCP server (usually your router). DHCP leases an address for a period of time — your IP can change when the lease expires.
Servers and infrastructure usually have static IP addresses — manually configured and fixed. This matters because a web server's domain name must reliably resolve to the same IP.
At the top level, blocks of public IP addresses are managed by regional registries (ARIN, RIPE, APNIC etc.) and delegated down to ISPs, then to customers.
What an IP address can reveal
An IP address can be looked up in public databases (ASN registries) to find the approximate location (usually city level), the ISP or organisation it belongs to, and the Autonomous System Number (ASN). It cannot pinpoint an exact physical address — that requires a warrant served to the ISP.