Open your network settings and you’ll probably see an address like 192.168.1.23. Open the homepage of this site and you’ll see a completely different one. Both are your IP address — one private, one public.
Private addresses
Private addresses are reserved for use inside local networks and are never routed on the public internet. For IPv4 there are three ranges (RFC 1918):
10.0.0.0/8— common in companies and cloud networks172.16.0.0/12— used by Docker and some corporate networks192.168.0.0/16— the default for most home routers
Anyone can use them, so millions of networks use the same addresses at the same time without conflict. IPv6 has an equivalent, unique local addresses (fd00::/8), though IPv6 networks usually give devices public addresses directly.
Public addresses
A public address is unique worldwide and assigned through the registry system to an ISP or organisation. It’s the address websites, game servers and email servers see when you connect.
NAT connects the two
Your router has a public address on its internet side and a private network behind it. Network address translation rewrites outgoing packets so they come from the router’s public address, and keeps a table so replies find their way back to the right device. That’s why every device in your home shows the same public IP.
Carrier-grade NAT
Because IPv4 addresses are scarce, many ISPs — especially mobile carriers — add a second layer of NAT. Your router then gets an address from 100.64.0.0/10 (shared address space, RFC 6598) and many customers share one public address.
You can tell if you’re behind CGNAT: compare the WAN address in your router’s status page with the address shown on this site. If they differ, your provider is translating again. Port forwarding and hosting services from home won’t work in that situation unless you use IPv6 or ask your ISP for a public address.
Does a private address protect me?
Partly. NAT means unsolicited inbound connections can’t reach your devices directly, which acts like a basic firewall. But it isn’t a security feature by design — a proper firewall still matters, especially with IPv6 where devices are directly addressable.
Which address do websites see?
Only the public one. The private address never leaves your local network. And with CGNAT or a VPN, websites see the carrier’s or VPN’s address, not even your router’s.
Look up any address with the IP lookup — private and special-purpose ranges are recognised and explained instead of being looked up.