Public vs private IP address

If you've run ipconfig and seen 192.168.1.23, then visited this site and seen something different — that's because your device has a private address and your connection has a public one.

Public IP address

Your public IP is assigned by your internet provider to your router or mobile connection. It is routable on the internet, and it's what websites and apps see when you connect — the address shown on the home page.

Private IP address

A private IP is used inside a local network. RFC 1918 reserves three IPv4 ranges for private use; they aren't routed on the public internet, so the same addresses are reused in countless separate networks:

In IPv6, the equivalents are unique local addresses (RFC 4193, starting fd) and link-local addresses (RFC 4291, starting fe80).

How NAT connects them

Your router performs NAT (Network Address Translation): for outgoing traffic it replaces the device's private address with its public one and keeps track of the session so replies reach the right device (RFC 3022). That's how the devices in a home share one public IPv4 address.

Laptop 192.168.1.23 ─┐
Phone  192.168.1.45 ─┼─► Router (NAT) ─► Internet sees 203.0.113.42
TV     192.168.1.60 ─┘

What about carrier-grade NAT?

Some ISPs add a second layer of NAT and share public IPv4 addresses between customers. RFC 6598 reserves 100.64.0.0/10 (100.64.0.0 – 100.127.255.255) for this. If your router's WAN address is in that range, or doesn't match the address this site shows, you're likely behind carrier-grade NAT — which can stop inbound connections such as port forwarding from working.

Public vs private at a glance

Step-by-step instructions: How to find your IP address.