Public IP vs Private IP

The core distinction

Every device on the internet needs an address to send and receive data — but not all IP addresses are visible on the public internet. There are two distinct categories:

• Public IP addresses are globally unique and routable across the internet. When you load a website, the server sees your public IP. This is the address iptool displays.
• Private IP addresses are used within local networks — your home, office, or data center. They are not routable on the public internet and are reused by millions of networks simultaneously.

Private address ranges

Three IPv4 address ranges are reserved exclusively for private use by RFC 1918:

10.0.0.0    – 10.255.255.255    (10.x.x.x)
172.16.0.0  – 172.31.255.255   (172.16–31.x.x)
192.168.0.0 – 192.168.255.255  (192.168.x.x)

If you check your device's IP settings and see an address in one of these ranges, that is your local network address — not what the internet sees when you connect to it.

How NAT bridges the two

Network Address Translation (NAT) is the mechanism that lets many private-addressed devices share a single public IP. Your home router sits at the boundary between your private network and the internet. Outgoing traffic has its source address rewritten from your device's private IP to your router's public IP. Incoming responses are translated back and forwarded to the correct device.

This means an entire household — with a laptop, phone, tablet, smart TV, and game console — can all appear on the internet as a single IP address. NAT was originally designed as a stopgap for IPv4 address exhaustion, but it became so widely deployed that it is now a fundamental part of how the internet works.

IPv6 and the end of NAT?

One of the key goals of IPv6 is to make NAT unnecessary. With 2¹²⁸ available addresses, every device in the world can have a unique, globally routable IPv6 address without any translation layer. In principle, this simplifies networking significantly — devices can communicate directly without relying on a router to rewrite their addresses.

In practice, many networks still use NAT even with IPv6 for security or policy reasons, but native IPv6 connectivity allows for true end-to-end addressability.

Why does it matter?

• Remote access — if you want to connect to a device on your home network from the internet (e.g., a home server or security camera), you need to know your public IP, not your device's private IP.
• VPN verification — when using a VPN, your public IP should change to the VPN server's address. iptool lets you confirm this instantly.
• Privacy — your public IP can reveal your approximate location and ISP. Your private IP reveals nothing to the outside world.