Public vs private IP addresses: what's the difference?

When someone asks "what's my IP address?", the honest answer is "which one?". Most people don't realise this, but you almost always have at least two IP addresses at the same time — and they're not the same kind of thing at all.

One identifies your individual device on your home or office network. The other identifies your network as a whole on the public internet. Both are real. Both are useful. Confusing them is the source of an enormous amount of networking frustration.

If you've already read the introduction to IP addresses, you've seen this distinction in passing. This post is the focused version: what each address is, when each one matters, and why you can't get away with knowing only one of them.

The private IP

Your private IP is the address your router hands out to your laptop when you connect to WiFi. It identifies your device — and only your device — within your local network. If you check your laptop's network settings right now, you'll see something that starts with 192.168, 10., or occasionally 172.16 through 172.31.

Those three prefixes aren't accidental. They come from three address ranges set aside specifically for private networks by a 1996 standard called RFC 1918. The RFC 1918 deep dive covers exactly which ranges, the math behind their sizes, and why those particular blocks were chosen — but the short version is: any device on any private network can use any address from those ranges, freely and without coordination.

The key thing about private addresses is that they're only meaningful inside the network they belong to. Two homes can both have a laptop sitting at 192.168.1.5 and a printer sitting at 192.168.1.10, and there's no conflict — because those addresses never leave their respective networks. The public internet doesn't see them. Your ISP doesn't route them. They exist purely so that the devices behind a single router can address each other.

The public IP

Your public IP is the address the rest of the internet sees. It's assigned to your router by your ISP — Comcast, Verizon, BT, Reliance Jio, whoever you pay every month — and at any given moment, it's globally unique. No other network on earth shares that exact address right now.

This is the address that shows up when you visit Network Lookup's IP lookup page. It's the one every website you visit logs in their access logs. It's what geolocation databases use to guess your approximate location, what registries tie back to your ISP and ASN, and what determines whether a streaming service thinks you're in a region where their content is licensed.

If your private IP says "where I am inside the house", your public IP says "where the house is". The two answer entirely different questions, and neither one is sufficient on its own.

The translation in the middle

These two addresses get connected by something called NAT — network address translation. NAT lives in your router and is invisible to everything else.

Here's what happens when your laptop loads a webpage. Your laptop sends a packet with a source address of 192.168.1.42 (its private IP) heading out toward the website. Your router intercepts that packet on the way out, rewrites the source address from 192.168.1.42 to its own public IP, and records the substitution in a translation table. The website receives a request that appears to come from your public IP — it has no way of knowing your laptop's private address even exists.

When the response comes back, the router sees a packet addressed to its public IP, looks up the translation table, sees that this connection corresponds to 192.168.1.42, rewrites the destination back to your laptop, and forwards it on the local network. Every device behind your router is going through the same translation, all sharing the same single public IP for outbound traffic.

How to find each one

Finding your public IP is one click — visit /ip on Network Lookup and it'll show you exactly what address websites see, alongside your apparent location, your ISP, and your ASN. (If you instead want to find another website's IP rather than your own, that's a different question, and the how to find a website's IP guide walks through the methods.)

Finding your private IP requires looking at your own machine, since no external service can see it:

• Windows: open Command Prompt and run ipconfig. The IPv4 address listed under your active network adapter is your private IP.
• macOS: open a terminal and run ifconfig | grep inet, or open System Settings → Network and click the active interface.
• Linux: ip addr show is the modern tool; ifconfig still works on most distributions.

Or, if you'd rather avoid the command line, log into your router's admin page (usually at 192.168.1.1 or 192.168.0.1) and look at the connected-devices list — every device with a private IP appears there, often with its name alongside.

Why the difference matters

Knowing the distinction makes three common situations make sense.

Setting up devices on your local network. When you add a printer, a smart-home hub, a NAS, or any other local device, you almost always need its private IP — not its public one. Your phone's printing app needs to know "where on this WiFi network is the printer", not "where on the internet is the printer". The private IP is the answer. Trying to use a public IP here doesn't work because the device isn't directly reachable from outside your network.

Hosting a game server, remote-desktop session, or self-hosted application. Now you do need your public IP, because someone outside your network is trying to reach in. But knowing the public IP isn't enough — you also have to configure your router to forward incoming connections on a specific port to the right private IP inside your network. This is what port forwarding means: telling your router that traffic arriving on port 25565 (for instance) should be sent to the device at 192.168.1.42, not just dropped.

Privacy. Your public IP is something every website you visit can log. It reveals your approximate location, your ISP, your ASN, and whether you appear to be using a VPN. Your private IP reveals nothing — it's not visible outside your network, so it can't be tracked, correlated, or geolocated. From a privacy standpoint, the public IP is the one to think about.

The IPv6 wrinkle

The whole public/private/NAT model is an IPv4 invention. It exists because IPv4 ran out of addresses and we needed a way to share. IPv6 has so many addresses — about 340 undecillion of them — that there's no need for the workaround. Every device on an IPv6 network can have its own globally routable address with room to spare.

In a fully IPv6 deployment, the distinction between "public" and "private" mostly dissolves: every address is public. Privacy is handled differently — through temporary "privacy" addresses that rotate over time, so the address a website sees today isn't the one it would see tomorrow. The IPv6 guide covers how this works in practice and why your device probably has several IPv6 addresses simultaneously, each serving a different purpose.

For now, though, the dual-IP world is still the norm for most people most of the time. Knowing the difference between the two — and which one to reach for in which situation — is one of those small pieces of knowledge that makes everything else in networking click into place. And if you ever need to plan a network or sub-divide an address block, the CIDR calculator handles the math.