What Is an IP Address? IPv4 vs IPv6 Explained
An IP (Internet Protocol) address is a unique number that identifies a device on a network so data can be routed to it. IPv4 addresses look like 192.168.1.1 — four numbers from 0–255. IPv6 addresses are longer hexadecimal strings that vastly expand the available space. Without IP addresses, devices couldn't find each other on the internet.
Here's what an IP address is, the two versions in use, and the key distinctions you'll run into.
What an IP Address Does
Every device that communicates on a network needs an address, just like a house needs a mailing address. When you load a website, your device's IP is the "return address" so the server's response finds its way back. IP addresses make routing — moving packets across networks — possible.
IPv4: The Familiar Format
IPv4 is 32 bits, written as four numbers (octets) separated by dots:
192.168.1.1
Each octet ranges 0–255, giving about 4.3 billion possible addresses. Under the hood it's just binary — 192.168.1.1 is 11000000.10101000.00000001.00000001. See it for yourself with our IP to Binary tool.
The problem: 4.3 billion addresses isn't enough for today's internet, which led to IPv6 and workarounds like NAT and private addressing.
IPv6: The Bigger Address Space
IPv6 is 128 bits, written as eight groups of hex digits:
2001:0db8:85a3:0000:0000:8a2e:0370:7334
That's roughly 340 undecillion addresses — enough for every device imaginable. IPv6 also simplifies routing and removes the need for NAT. Adoption is steadily growing alongside IPv4 (most networks run both).
Public vs Private IP Addresses
- Public IP — globally unique, routable on the internet, assigned by your ISP.
- Private IP — used inside a local network, not routable on the internet. Reserved ranges include
10.0.0.0/8,172.16.0.0/12, and192.168.0.0/16.
Your router has one public IP and hands out private IPs to your devices, translating between them with NAT. That's why every device in your home can share a single public address.
Static vs Dynamic IP Addresses
- Dynamic — assigned automatically by DHCP and may change over time. The default for most devices.
- Static — manually fixed so it never changes; used for servers and services that must be reliably reachable.
See What Is a Static IP Address? for when you need one.
Subnets and CIDR
Networks are divided into subnets using a subnet mask or CIDR notation (192.168.1.0/24). This controls how many addresses a network holds and how routing decisions are made. Plan them with our Subnet Calculator and CIDR Calculator, and read Subnet Mask Cheat Sheet and CIDR Notation Explained.
Frequently Asked Questions
What is an IP address? A unique number identifying a device on a network so data can be routed to and from it.
What does an IP address look like?
IPv4 looks like 192.168.1.1 (four numbers 0–255); IPv6 looks like 2001:0db8:85a3::8a2e:0370:7334 (eight hex groups).
What is the difference between IPv4 and IPv6? IPv4 is 32-bit with ~4.3 billion addresses; IPv6 is 128-bit with a virtually unlimited supply and simpler routing.
What is the difference between a public and private IP? A public IP is globally routable and assigned by your ISP; a private IP is used within a local network and isn't reachable directly from the internet.
Can an IP address identify me? It can reveal your approximate location and ISP, but not your exact identity by itself. A public IP is tied to your network, not your name.
Related Reading
An IP address is simply the address of a device on a network. Master IPv4 vs IPv6 and public vs private, and the rest of networking — subnets, NAT, routing — starts falling into place.