An IP (Internet Protocol) address is a number that identifies a device on a network, like 192.168.1.23 or 2001:db8::1. Routers use it to deliver data to the right place. Your home devices usually have private addresses and share one public address assigned by your ISP.
How it works
Every packet carries a source and destination IP address. Routers read the destination and forward the packet towards it, hop by hop, using their routing tables.
Public and private
- Private addresses are for use inside homes and organisations: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. The same private address exists in millions of networks, so they can't be used on the internet.
- Public addresses are unique worldwide and routable on the internet. Your ISP gives your router one (or shares one between customers with CGNAT).
- Your router translates between them with NAT: outgoing traffic appears to come from the router's public address.
Dynamic and static
Most addresses are dynamic: assigned automatically by DHCP and possibly changing over time. A static address is configured to stay the same, which servers and some business connections need.
IPv4 and IPv6
IPv4 addresses are 32 bits (four numbers 0–255); IPv6 addresses are 128 bits written in hex. Most devices have both.
What an IP address reveals
A public IP shows your ISP and an approximate location, typically the city or region. It doesn't reveal your name or street address.
Examples
| Address | Kind |
|---|---|
| 192.168.1.23 | Private IPv4 (home network) |
| 10.0.0.19 | Private IPv4 |
| 100.74.95.254 | Carrier-grade NAT (shared address space) |
| 17.253.144.10 | Public IPv4 (Apple) |
| 127.0.0.1 | Loopback: this computer |
| 2001:db8::1 | IPv6 (documentation range) |
On a Mac
- Your local IP: System Settings › Network › Wi-Fi › Details › TCP/IP, or
ipconfig getifaddr en0. - Your public IP:
curl -s https://api.ipify.org, ordig +short txt ch whoami.cloudflare @1.1.1.1in Terminal. - The IPs your apps talk to:
lsof -nP -i -sTCP:ESTABLISHED.
See it in the app
LightAtom's Map turns the IP addresses your apps connect to into places, drawing arcs from your home to each server, and its connections view shows the domain behind each address.
Frequently asked questions
What is my IP address?
You have two: a private one on your home network (System Settings › Network › Details) and a public one that websites see. Run curl -s https://api.ipify.org in Terminal to see the public one.
Can someone find my location from my IP address?
Only approximately: usually your city or region, and your ISP. Your exact address is known only to your ISP.
Why does my IP address change?
Most ISPs assign dynamic addresses that can change when your router restarts or its lease ends. Private addresses at home can also change unless the router reserves one for your device.
What is the difference between an IP address and a MAC address?
An IP address identifies a device's position on a network and is used for routing. A MAC address identifies a network interface on the local link only.
Is 192.168.1.1 my IP address?
Usually that's your router's private address. Your Mac has its own, such as 192.168.1.23.