An IP address (Internet Protocol address) is a number that identifies a device's network interface. Every packet your device sends carries a source and destination address, so replies know where to come back to (RFC 791). Think of it as the return address on an envelope.
What does an IP address look like?
There are two versions in use today:
- IPv4 — a 32-bit address written as four numbers from 0 to 255 separated by dots, e.g.
203.0.113.42(RFC 791). - IPv6 — a 128-bit address written as groups of hexadecimal digits separated by colons, e.g.
2001:db8:85a3::8a2e:370:7334(RFC 8200).
A connection can have both. The home page checks each one separately.
Who gives you an IP address?
- Your internet provider (ISP) assigns a public IP address to your router or mobile connection. This is the address websites see, and the one this site shows you.
- Your router usually hands out private addresses (like
192.168.1.23, from the ranges in RFC 1918) to the devices on your home network, using DHCP (RFC 2131).
The router translates between the two using NAT (RFC 3022), so the devices at home share one public IPv4 address. See Public vs private IP addresses.
Does my IP address change?
It can. Addresses handed out by DHCP are leased for a limited time (RFC 2131), so a dynamic address may change when the lease ends or your router reconnects. A static IP stays the same. See Static vs dynamic IP.
What can someone learn from my IP address?
Mostly your internet provider and an approximate location. MaxMind, a major IP geolocation provider, describes its results as “an approximate location, not a precise one” and says city-level accuracy typically ranges from 20% to 75% (MaxMind). See What does my IP address reveal?
Quick summary
- An IP address identifies your device on a network.
- IPv4 looks like
203.0.113.42; IPv6 looks like2001:db8::1. - Your ISP gives you a public IP; your router gives each device a private IP.
- It points to your ISP and a rough location — not a precise one.