An IP address (Internet Protocol address) is a unique numerical identifier assigned to every device connected to a network. It serves two functions: identifying the device ("who is it?") and locating it within the network topology ("where is it?").
IPv4 vs IPv6
- IPv4 — 32-bit address, written as four decimal numbers separated by dots:
192.168.1.1. Supports ~4.3 billion unique addresses — exhausted in 2011. - IPv6 — 128-bit address, written as eight groups of hexadecimal digits:
2001:0db8:85a3:0000:0000:8a2e:0370:7334. Supports 340 undecillion addresses — practically unlimited.
Public vs Private IP Addresses
- Public IP — Assigned by your ISP; unique on the internet. Your router has one. Websites have one (or several).
- Private IP — Used within a local network (home, office). Reserved ranges:
192.168.x.x,10.x.x.x,172.16-31.x.x. Not routable on the internet.
Static vs Dynamic IP Addresses
- Static IP — Fixed; never changes. Required for servers, DNS and services that need a consistent address.
- Dynamic IP — Changes periodically; assigned by DHCP. Used by most home internet connections.
IP Addresses and Websites
Web servers have static public IP addresses. DNS A records map your domain name to this IP. When you use a CDN or shared hosting, multiple domains may share the same IP address. Use our DNS Lookup tool to see which IP a domain resolves to.