An IP address is the number that identifies a device on a network, so data knows where to go. Every server, phone and laptop online has one. Domain names exist so people do not have to remember them; DNS turns names into IP addresses.
IPv4 and IPv6
| IPv4 | IPv6 | |
|---|---|---|
| Looks like | 203.0.113.10 | 2001:db8:85a3::8a2e:370:7334 |
| Length | 32 bits | 128 bits |
| How many | About 4.3 billion | About 340 undecillion |
| DNS record | A | AAAA |
IPv4 ran out of new addresses years ago, which is why IPv6 exists. Most of the internet now runs both side by side. In an IPv6 address, :: stands for a run of zeros, so it can be written shorter.
Public and private addresses
Your home router has one public address that the internet sees. Devices behind it get private addresses, which are reused in millions of homes and never appear on the internet:
10.0.0.0to10.255.255.255172.16.0.0to172.31.255.255192.168.0.0to192.168.255.255
The router translates between them, a process called NAT. A server meant to be reached from the internet needs a public address.
Static and dynamic
Home connections often get a dynamic public address that can change. Servers get a static address that stays the same, which is what DNS records point to.
Find yours
curl -4 ifconfig.me
curl -6 ifconfig.me
ip addrThe first two show the public addresses the internet sees (IPv4 and IPv6). ip addr on Linux (or ipconfig on Windows) lists the addresses on the machine’s own network cards.
What the slash means
You will see addresses like 203.0.113.0/24. The number after the slash says how many bits are the network part. A /24 covers 256 addresses (203.0.113.0 to 203.0.113.255); a single IPv4 address is a /32.
Something out of date? Software changes. If a step no longer works, tell us and we will check it and update the page.
