Every connected home has at least two kinds of IP address working at the same time. A public IP is assigned by your internet provider, is unique across the whole internet, and is what every website sees. Private IPs are assigned by your router to each device inside your network, come from ranges set aside for exactly that job, and are reused in millions of other homes at once. The router sits between the two and translates. This guide explains how that works, why the ranges are what they are, and how to find both of yours.
The difference in one table
| Public IP | Private IP | |
|---|---|---|
| Assigned by | Your internet provider | Your router (DHCP) |
| Unique | Worldwide | Only within your network |
| Reachable from the internet | Yes | No |
| Typical form | 203.0.113.42 or 2001:db8::1 | 192.168.1.23, 10.0.0.5, 172.16.4.2 |
| Who sees it | Every website and service you use | Only devices on your own network |
| How to find it | What Is My IP on our homepage | Device network settings or ipconfig |
Why private ranges exist
IPv4 has about 4.3 billion addresses, and by the early 1990s it was clear they would run out. Rather than give every device in every home a globally unique address, the internet’s engineers reserved three blocks for private use in RFC 1918. Any network can use them freely because routers on the public internet drop packets addressed to them. The blocks are:
| Range | CIDR | Addresses | Where you see it |
|---|---|---|---|
| 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 | 16,777,216 | Large offices, Xfinity and Telstra gateways |
| 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 | 1,048,576 | Docker, cloud networks, some enterprise Wi-Fi |
| 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 | 65,536 | Almost every home router |
A fourth block, 100.64.0.0/10, was added later for providers who run carrier-grade NAT, sharing one public address among many customers. If your router’s WAN address begins 100.64 through 100.127, that is what your provider is doing.
How NAT joins the two
When your laptop at 192.168.1.23 asks for a web page, the router rewrites the request so that it appears to come from your public IP, notes which device asked and on which port, and sends it on. When the reply arrives at the public IP, the router looks up the note and delivers it to 192.168.1.23. That process is network address translation, and it is why a whole household can share one public address. It also means an unsolicited connection from the internet has nowhere to go: the router has no note for it, so it is dropped. That is the accidental firewall that keeps most home devices out of reach.
What your public IP reveals
Your public IP identifies your provider and usually your city or region, but not your street address. Geolocation databases map address blocks to the places providers announce them from, which is accurate to a country almost always, to a city often, and to a house essentially never. Mobile connections and VPNs can place you hundreds of miles away. The What Is My IP tool shows your address, country and connection type as sites see them.
Public IPs change; private ones can be fixed
Most residential public addresses are dynamic: the provider can change them when the router reconnects or on a schedule. Businesses pay for static addresses that never change. Inside your network, the router usually assigns private addresses dynamically too, but you can reserve one for a printer, camera or game console under DHCP reservation in the router’s settings so that port forwarding keeps working. The router’s own private address is the gateway; our guide covers how to find your router IP on any device.
IPv6 changes the picture
IPv6 has so many addresses that every device can hold a globally unique one, and NAT is no longer needed. Instead, a firewall on the router decides what may come in. Google’s own measurements show well over 40% of its users now connect over IPv6, and most home connections carry both protocols at once. The private-address idea still exists in IPv6 as unique local addresses, fc00::/7, but home routers rarely use them.
The special addresses that are neither
A few addresses are reserved for fixed jobs. 127.0.0.1 is loopback, meaning this device; 0.0.0.0 means no particular address; 169.254.x.x is what a device gives itself when no router answers; 255.255.255.255 is broadcast to everyone on the local network. Our IP addresses reference lists them all.