Public vs. Private IP Address: How Are They Different?

An IP address is a numeric or alphanumeric identifier assigned to a router or device. It helps direct traffic on the internet to the correct location. Your postal address is a real-world parallel of an IP address. It helps the postal department deliver letters to the correct recipient.

While most users know about an IP address, many aren’t aware that there are two kinds of IP addresses. These are private IP addresses and public IP addresses. Both play an important role in connecting users to the internet.

This article breaks down the differences between public and private IP addresses. We explain the utility of each and highlight the role they can play in keeping your internet activity private and secure.

Public IP Address vs. Private IP Address: Overview

A public IP address refers to the unique identifier assigned to your internet connection by your internet service provider. Your router uses your public IP address to identify you with the rest of the internet.

This ensures that websites, emails, and other content on the internet reach you correctly.

On the other hand, the private IP address identifies different devices connected to the same local network. Once your router has received information from the global network, it needs to know which device to send it to.

The private IP address helps the router identify different devices on your network and forward the information correctly.

The following table captures the major differences between a public and a private IP address. A breakdown of both kinds of IP addresses is provided in the next section.

What Is a Public IP Address?

A public IP address is an IP assigned to your router by your internet service provider. It’s also known as an external IP address since websites, servers, and apps on the global network use it to identify you. The visualization below should help understand how a public IP address works.

A public IP address acts as your gateway to the internet, and you usually can’t go online without one. Your public IP address must be visible to sites and web pages to correctly communicate with websites.

What Is a Private IP Address?

Your router sends data packets from connected devices to servers on different websites. Once packets are received, they need to be forwarded to the relevant device. With several devices connected to the router at one time, it uses your private IP address to distinguish and relay this information.

It can do this by using your device’s private IP address, a numerical identifier assigned to each device on the local network. A private IP address is also known as the local IP address.

Think of the private IP address as the room, floor, or dorm number on your postal address. Once the letter arrives at your building, the specific room/floor number helps ensure the letter reaches you instead of any other residents.

Unlike a public IP address, your private IP address is not visible to other websites. Instead, it’s only visible to other devices on your network. You can usually check the private IP addresses of all devices connected to the router via its settings.

What Are the Differences Between Private and Public IP Addresses?

Now that we know what public and private IP addresses are, let’s understand the key differences between them.

Utility

As the previous section illustrates, both public and private IP addresses serve different purposes. While your router uses the public IP address to identify you to websites on the internet, the private IP address is used to identify different devices on your local network.

However, both private and public IP addresses work together to provide internet connectivity. Websites on the internet send information to your router using a public IP address. Your router then forwards this information to the relevant device’s private IP address using network access translation (NAT).

But why are private IP addresses needed in the first place? Why can’t each device have its own unique external IP? To answer this question, let’s first understand what IPv4 is. IPv4 is the most widely used internet protocol. It was launched in 1970 and comprises 32-bit numeric strings.

As a result, it can only support 4 billion unique addresses, which is obviously less than the number of connected devices out in the world today. Therefore, allotting private IP addresses to devices on the same network is a way to conserve IPv4 addresses.

However, we are in the midst of a transition to IPv6 which comprises 128-bit alphanumeric strings. Hence, IPv6 supports 340 undecillion possible combinations, which should be more than enough for the foreseeable future!

Predetermined ranges

Both public and private IP addresses fall within certain predetermined ranges of numeric strings to make the entire framework systematic and logical. The Internet Assigned Numbers Authority (IANA) distributes private IP addresses to companies worldwide. IP addresses used by some of the leading router manufacturers are:

Conversely, public IP addresses usually comprise numeric strings not assigned to any private ID addresses. Moreover, each public IP address is unique and cannot be reused while private IP addresses are regularly reused across different routers.