IPv4 vs. IPv6: What's the Difference?

IPv6 lets more devices use the internet

There are two Internet Protocol (IP) types: IPv4 and IPv6. The former is currently much more common, but they're both IP addresses that provide the same function, which is to allow your computer, phone, and other network devices to communicate with servers and more over the internet.

You've probably never had an IPv4-related issue that stopped you from going online, so you might wonder why IPv6 is even a thing. What does an upgraded IP do? Is IPv6 better than IPv4?

World map showing connections
KTSDESIGN / Science Photo Library / Getty Images

Let's look at what these terms mean and how they're different.

What IPv4 and IPv6 Mean

IPv4 stands for IP version 4. It was developed by DARPA and started being used in 1983, and is still widely used today. You’ve probably seen an IPv4 address—they're presented in dot-decimal notation like this, where there are four sections of numbers separated by periods:

IPv6 stands for IP version 6. Developed by the Internet Engineering Task Force and introduced in 1995, it was designed to eventually replace IPv4, but is currently used in conjunction with it. An IPv6 address looks a lot different from an IPv4 address because it can include letters and separates its sections with colons. IPv6 uses eight 16-bit hexadecimals:


Why There Are Two

IP version 6 was created to improve on the limitations of IPv4. Although the second iteration was introduced a mere decade after the first, the primary reason it's needed is because of the expansive nature of the internet. 

One way IPv6 is different from IPv4 is in the structure of the address. Instead of allowing a 32-bit address like IPv4, IPv6 supports 128-bit addresses. Beyond the 0-9 digits that IPv4 supports, IPv6 accepts letters a-f. With each additional bit, the address space (the total number of unique IP addresses) doubles in size. 

This means more IP addresses can be created with IPv6 vs IPv4. While the former is limited to just over 4 billion, IPv6 can create 340 undecillion unique addresses (that’s 340 billion billion billion billion!).

If we pretend every single individual on Earth has just one device that needs access to the internet, billions of devices would be refused access immediately in an IPv4-only world. Plus, as more devices are added to the internet every day—like smartwatches, phones, and cars—it’s clear that the 4 billion IP address limitation set by IPv4 simply won’t cut it forever.

Governing authorities limit how many IPv4 and IPv6 addresses are available for public use, but there's still far more IPv6 IP address combinations than IPv4. It's highly unlikely that we'll run out of them anytime soon.

Other Differences Between IPv6 and IPv4

A larger address space isn't the only difference between IPv4 and IPv6. Here are some other distinctions:

IPv6 and IPv4 Differences
  IPv6 IPv4
Header Fields 8 12
Header Field Length 40 20
Has Checksum Fields No Yes
Transmission Types Unicast, multicast, anycast Unicast, broadcast, multicast
VLSM Support No Yes
Assignment Types DHCPv6 and static DHCP and static
Security Built-in IPSec support Depends on the application
Automatic Configuration Yes No
Mapping Method NDP (Neighbor Discovery Protocol) ARP (Address Resolution Protocol)
Direct P2P Connections Yes No (because of Network Address Translation)

Is IPv6 More Secure Than IPv4?

Although IPv6 is newer and so you might assume that everything in the name of security is also better, that's not quite true. IPv6 and IPv4 both suffer from address flooding, man-in-the-middle attacks, packet captures, and more.

IPv6 includes built-in support for IPSec (Internet Protocol Security), which is the same thing VPNs use to encrypt data. It might seem that IPSec immediately makes IPv6 superior, but IPSec implementation is only recommended, not required. Plus, it can be used IPv4, too, so there's little difference there.

An auto-configuration feature is supported by IPv6, which lets devices generate an IP address based on their MAC address. This could potentially be used by hackers or third-party companies to track people by their hardware.

However, IPv6 has the upper hand when it comes to using NDP vs ARP. IPv4 suffers from ARP-related issues like spoofing, MAC flooding, and MAC duplicating. IPv6 improves on this by using the Secure Neighbor Discovery (SEND) protocol to secure NDP with cryptographically generated addresses. There's a lot more on this in this Super User thread.

For most of us, the important takeaway is that switching over to IPv6 won't fix the major problems that plague internet-related activity, like viruses, data theft, monitoring, etc. While there are fundamental differences between how IPv6 and IPv4 work, plenty of threats are still very real whether you use IPv6 or IPv4.

What You Need to Do to Use IPv6

For end-users that aren’t running web services or creating networking devices, using IPv6 instead of IPv4 is really just a waiting game. You don't need to prepare your computer for IPv6 or learn anything new about IP addresses in general.

There won't come a time when you’re suddenly shut off from the internet because you didn’t type in an IPv6 address to replace the old IPv4 one. IPv6 and IPv4 will continue to work side by side until IPv6 is available for every device around the globe, which will take many years to complete.

You can monitor Google's stats on IPv6 adoption to see the upward trend of IPv6 use by Google users.

When the transition happens at your home, on your phone, etc., it will be as seamless as your IPv4 address changing to a different one, something that happens often and that you never notice.

However, if your device and ISP support it, you can switch over to IPv6 manually whenever you want. Look for the option in your router's settings. Google Wifi, for example, includes a toggle to enable IPv6 in the Advanced networking area of the app.

Another area where you might use an IPv6 address is when changing DNS servers. This list of free and public DNS servers include some examples of companies that offer IPv6 versions of their DNS servers.

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