IPv4 vs IPv6: What’s the Difference?

IPv4 and IPv6 are two versions of the Internet Protocol. IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses and provides a vastly larger address space. Both are still used on the internet today.

This article compares the two in plain language: how their addresses look, why IPv6 was created, how NAT fits in, and what it all means for speed, security, and everyday use. If you are new to the topic, it may help to first learn how IP addresses work.

What Is IPv4?

IPv4 is Internet Protocol version 4, the version that carried most internet traffic for decades. Its addresses are 32 bits long and are written in dotted-decimal notation: four numbers from 0 to 255 separated by dots, such as 192.0.2.1. That particular address comes from a range reserved for documentation, so it is safe to use in examples and does not belong to a real connection.

A 32-bit address allows about 4.3 billion possible values. That number is only a ceiling. Some blocks are reserved for special purposes, such as private networks, so not all of those values are available as ordinary public addresses.

What Is IPv6?

IPv6 is Internet Protocol version 6. Its addresses are 128 bits long and are written in hexadecimal, in groups separated by colons, such as 2001:db8::1. This one also comes from a documentation range.

Because the addresses are long, IPv6 allows a shortcut: a double colon (::) can stand in for one run of consecutive groups that are all zeros. The full form of the example above has eight groups, and the double colon fills in the zero groups between the first part and the last. The address space is vastly larger than IPv4's, large enough that running out of addresses is not a practical concern.

IPv4 vs IPv6: Key Differences

The table below summarizes the main differences. Real networks can vary, so treat it as a general overview.

Why Was IPv6 Created?

IPv4 was designed when only a small number of computers were expected to be connected. As the internet grew to include home computers, phones, tablets, game consoles, TVs, and many other connected devices, the supply of unused IPv4 addresses became a real constraint. This is often called IPv4 address exhaustion.

IPv6 was designed to solve that problem by providing a dramatically larger address space. IPv4 did not suddenly stop working as a result, and IPv6 has not replaced it. Networks have been adding IPv6 gradually while continuing to support IPv4, and the two coexist.

What Is NAT and Why Is It Common with IPv4?

Network Address Translation (NAT) lets many devices on a local network share one public IP address. Your router gives each device a private address for use inside your home, and when a device contacts the internet, the router translates the connection so it appears to come from the single public address your ISP assigned. When replies come back, the router sends them to the right device.

NAT became common with IPv4 because public IPv4 addresses are limited, and it is a big reason a typical household can get by with one. If you would like more detail on public and private IP addresses, that article covers the common private ranges.

NAT is not exclusive to IPv4, and forms of it can be used with IPv6 as well. With IPv6, though, there are enough addresses that NAT is generally not needed to conserve them.

Is IPv6 Faster Than IPv4?

Neither version is automatically faster in every situation. The speed you experience depends on many things, including:

• Your ISP
• The network routing between you and the destination
• The website or server you are connecting to
• Your device
• Your network configuration
• The quality of the path your traffic takes

In some cases IPv6 may perform better, in others IPv4 may, and often the difference is too small to notice. It is not safe to assume that switching versions will make a connection faster.

Is IPv6 More Secure Than IPv4?

IPv6 includes modern protocol capabilities, but simply having an IPv6 address does not automatically make a connection secure. Real security depends on how a network is configured, whether firewalls are in place, how current your software is, whether connections are encrypted, and other factors.

Both versions need sensible protection. IPv6 does not make firewalls unnecessary, and it does not replace HTTPS or a VPN where you would otherwise use them.

Do I Need IPv6?

Most people do not need to choose manually. Your operating system, router, and ISP usually handle IPv4 and IPv6 connectivity automatically. Depending on the network, a connection might offer:

• IPv4 only: the network provides IPv4 and no IPv6.
• IPv6 only, with transition mechanisms: the network uses IPv6 and relies on additional technology to reach services that are still IPv4-only.
• Both (dual stack): the network provides IPv4 and IPv6 side by side.

Not having IPv6 is common and usually does not stop websites from working.

Why Do I Have Both IPv4 and IPv6?

That is called dual-stack connectivity. A device or network can have both kinds of addresses at once and use whichever is appropriate or reachable for a particular service. If a website supports IPv6 and your connection does too, the connection may use IPv6. If the site only supports IPv4, your device uses IPv4 instead.

This is why a lookup tool may show an IPv4 address, an IPv6 address, or both, and why different websites can see different addresses from the same device.

Can IPv4 and IPv6 Communicate Directly?

Not directly. IPv4 and IPv6 are different protocols with different address formats, so a device that speaks only one cannot simply talk to a device that speaks only the other.

Networks bridge the gap in several ways, such as running both protocols at once (dual stack), using translation technologies, or using proxies and other transition mechanisms that connect services across the two environments. For most users, this happens in the background.

How to Check Your IPv4 and IPv6 Address

WhatIsMyIP can show your public IPv4 and IPv6 address when they are available, along with network information such as your ISP. If one of them is not detected, that usually just means your connection does not use it. You can learn more about the site on the About page.

Check your IPv4 and IPv6 address

IPv4 vs IPv6: Which One Should You Use?

Ordinary users generally do not need to choose between them. The protocol that is available depends largely on your ISP, your network, your device, and the service you are connecting to. Leaving the default settings alone is usually the best approach.

Turning off IPv4 or IPv6 without a specific technical reason is not recommended, because it can cause some sites or services to work poorly or not at all. For information about how data may be processed when you use lookup tools, see the Privacy Policy.

Frequently Asked Questions