What Is a Public IP Address?

Definition of Public IP Address

Illustration of lines connecting to dots representing a network and its nodes
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A public IP address is an IP address that your home or business router receives from your ISP. Public IP addresses are required for any publicly accessible network hardware, like for your home router as well as for the servers that host websites.

Public IP addresses are what differentiate all devices that are plugged in to the public internet. Each and every device that's accessing the internet is using a unique IP address.

In fact, a public IP address is sometimes called an Internet IP.

It's this address that each Internet Service Provider uses to forward internet requests to a specific home or business, much like how a delivery vehicle uses your physical address to forward packages to your house.

Think of your public IP address as any other address you have. For example, your email address and your home address are both completely unique to you, which is why sending mail to those addresses ensures that they actually get to you and not someone else.

The same exclusivity is applied to your IP address so your digital requests are sent to your network... and not someone else's.

Private vs Public IP Addresses

A private IP address is, in most ways, the same thing as a public IP address. It's a unique identifier for all the devices behind a router or other device that serves out IP addresses.

However, unlike with public IP addresses, the devices in your home can have the exact same private IP addresses as your neighbor's devices, or anyone else's all around the world.

This is because private addresses are non-routable - hardware devices on the internet are programmed to prevent devices with a private IP address from communicating directly with any other IP beyond the router that they're connected to.

Because these private addresses are restrained from reaching the internet, you need an address that can reach the rest of the world, which is why a public IP address is needed.

This type of setup enables all the devices in your home network to relay information back and forth between your router and ISP using just a single address (a public IP address).

Another way to look at this is to think of the router in your home as your own Internet Service Provider. While your router serves out private IP addresses to the devices privately connected behind your router, your ISP delivers public IP addresses to the devices that are publicly connected to the internet.

Both private and a public addresses are used for communication, but the range of that communication is limited based on the address that's used.

When you try opening a website from your computer, the request is sent from your computer to your router as a private IP address, after which your router requests the website from your ISP using the public IP address assigned to your network. Once the request has been made, the operations are reversed - the ISP sends the address of the website to your router, which forwards the address to the computer that asked for it.

Range of Public IP Addresses

Certain IP addresses are reserved for public use and others for private use. This is what makes private IP addresses unable to reach the public internet - because they aren't even able to communicate properly unless they exist behind a router.

The following ranges are reserved by the Internet Assigned Numbers Authority (IANA) for use as private IP addresses:

  • 10.0.0.0 to 10.255.255.255
  • 172.16.0.0 to 172.31.255.255
  • 192.168.0.0 to 192.168.255.255

Excluding the addresses above, public IP addresses range from "1..." to "191...".

All of the "192..." addresses are not registered publicly, which means they can only be used behind a router as private IP addresses. This range is where most private IP addresses fall, which is why the default IP address for most Linksys, D-Link, Cisco, and NETGEAR routers is an IP within this set.

How to Find Your Public IP Address

You don't need to know your public IP address most of the time, but there are situations where having it is important or even necessary, like when you need to access your network, or a computer within it, from away from home or your business.

The most basic example would be when you're using a remote access program. So, for example, if you're in your hotel room in Shanghai, but need to "remote in" to your computer at home, in your apartment in Denver, you'll need to know the internet-accessible IP address (the public IP address your home router is using) so you can instruct that software to connect to the right place.

It's surprisingly easy to find your public IP address. While there are many ways to do it, just open one of these websites on your smartphone, laptop, desktop, or any other device that uses a web browser: IP Chicken, WhatsMyIP.org, Who.is, WhatIsMyPublicIP.com, or WhatIsMyIPAddress.com.

Although it's not quite as easy as using a website, can also usually find your public IP through your router's administration page. If you don't know what that is, it's usually your default gateway's IP address.

The catch? You'll need to do this from your home computer. If you're already away, you'd have to have a friend or coworker do it for you. You could also use a DDNS service, some of which are even free. No-IP is one example, but there are others.

Why Public IP Addresses Change

Most public IP addresses change, and relatively often. Any type of IP address that changes is called a dynamic IP address.

Back when ISPs were a new thing, users would connect to the internet for only a short amount of time, and then disconnect. An IP address that was being used by one customer would then be open for use by another that needed to connect to the internet.

This way of assigning IP addresses meant that the ISP wouldn't need to purchase such a large number of them. This general process is still in use today even though most of us are always connected to the internet.

However, most networks that host websites will have static IP addresses because they want to make sure that users can have constant access to their server. Having an IP address that changes would defeat the purpose, as DNS records would need to be updated once the IP changes, which might cause unwanted downtime.

Home networks, on the other hand, almost always are assigned dynamic IP addresses for the opposite reason. If an ISP gave your network an unchanging address, it may be more likely to be abused by customers who are hosting websites from home. This is one reason why having a static IP address is more expensive than having a dynamic IP address. DDNS services, which I mentioned earlier, are a way around this... to some degree.

Another reason most networks have public IP addresses that change is because static IP addresses require more management, and therefore normally cost more for a customer to have than a dynamic one.

For example, if you were to move to a new location a few miles away, but use the same ISP, having a dynamic IP address assignment would simply mean that you'd get another IP address that's available from the pool of addresses. Networks using static addresses would have to be re-configured to apply to their new location.

Hiding Your Public IP Address

You can't hide your public IP address from your ISP because all of your traffic has to move through them before reaching anything else on the internet. However, you can hide your IP address from the websites you visit, as well as encrypt all of the data transfers (thus hiding traffic from your ISP), by first filtering all your data through a virtual private network (VPN).

Say, for example, that you wanted your IP address to be hidden from Google.com. Normally, when accessing Google's website, they would be able to see that your specific public IP address has requested to view their website. Doing a quick search on one of the IP finding websites from above would tell them who your ISP is. Since your ISP knows which IP addresses have been assigned to you, specifically, would mean that your visit to Google could be pinned directly to you.

Using a VPN service adds another ISP at the end of your request, before you open Google's website.

Once connected to a VPN, the same process as above takes place, only this time, instead of Google seeing the IP address that your ISP has assigned to you, they see the IP address that the VPN has assigned.

So if Google wanted to identify you, they'd have to request that information from the VPN service instead of your ISP, because again, that's the IP address they saw access their website.

At this point, your anonymity hinges on whether the VPN service is willing to give up your IP address, which of course reveals your identity. The difference between most ISP's and most VPN services is that an ISP is more likely to be required by law to give up who it is that accessed the website, while VPN's sometimes exist in countries that have no such obligation.

There are lots of free and paid VPN services out there that all offer different features. Looking for one that never saves traffic logs may be a good start if you're concerned that your ISP is spying on you.

A few free VPN services include FreeVPN.me, CyberGhost, Hideman, and Faceless.ME.

More Information on Public IP Addresses

Routers are assigned one private address called the default gateway IP address. In a similar fashion to your network having one IP address that communicates with the public internet, your router has one IP address that communicates with other private networks.

While it's true that the authority to reserve IP addresses rests with IANA, they are not some sort of central source for all internet traffic. If an outside device is breaching your network, it has nothing to do with IANA.