IPv4 vs IPv6: Differences, Examples & Why It Matters
The IPv4 vs IPv6 comparison comes down to one big problem and its solution: the internet ran short of addresses, so a far larger system was designed to replace the original. Here is how the two formats differ and why it matters.
IPv4 vs IPv6 at a glance
When people compare IPv4 vs IPv6, they are really talking about two generations of the same idea: a numbering scheme that gives every device on the internet an address. IPv4 is the original, designed in the early era of networking, and it still carries a huge share of the world's traffic. IPv6 is its successor, created to solve the shortage of addresses that IPv4 eventually hit.
If you are brand new to the topic, our overview of what an IP address is covers the fundamentals first. Otherwise, let us dive into what sets the two versions apart.
Address formats and examples
The most visible difference is how the addresses are written.
An IPv4 address has four numbers from 0 to 255 separated by dots, for example 192.0.2.1. Under the hood it is a 32-bit number, which is why the total supply is capped.
An IPv6 address is a 128-bit number written as eight groups of hexadecimal digits separated by colons, for example 2001:0db8:0000:0000:0000:0000:0000:0001. To keep things readable, long runs of zeros can be compressed with a double colon, so that same address shortens to 2001:db8::1.
| Feature | IPv4 | IPv6 |
|---|---|---|
| Example | 192.0.2.1 | 2001:db8::1 |
| Size | 32 bits | 128 bits |
| Notation | Decimal, dot-separated | Hexadecimal, colon-separated |
| Address count | About 4.3 billion | Roughly 340 undecillion |
| Address translation | Widely used (NAT) | Rarely needed |
| Configuration | Manual or DHCP | Often self-configuring |
Why the internet needed IPv6
IPv4's 32-bit design allows for about 4.3 billion unique addresses. In the internet's early decades that felt endless, but the explosion of computers, phones, and connected gadgets meant the pool was always going to run dry. Eventually the central pools of fresh IPv4 addresses were handed out, an event covered in our guide to IPv4 address exhaustion.
IPv6's 128-bit design was the answer. It provides such a vast number of addresses, around 340 undecillion, that running out is not a practical concern. That abundance means every device can potentially have its own globally unique address without the workarounds IPv4 relies on.
IPv6 has so many addresses that you could assign a unique one to every grain of sand on Earth many times over and still have almost the entire supply left. Scarcity, the defining problem of IPv4, simply does not apply.
How they behave differently
Beyond raw size, the two protocols work differently in ways that matter to networks.
- Address translation. Because IPv4 addresses are scarce, most homes share one public address across many devices using NAT. IPv6 has enough addresses that this sharing is usually unnecessary.
- Configuration. IPv6 devices can often configure their own addresses automatically, whereas IPv4 typically leans on DHCP or manual setup.
- Header design. IPv6 uses a streamlined packet header that routers can process more efficiently than IPv4's more complex one.
Can the two work together?
IPv4 and IPv6 are not directly compatible, which is a big reason the transition has taken so long. A device speaking only IPv6 cannot talk to one speaking only IPv4 without help. The common solution is dual-stack, where networks and devices run both protocols at the same time and pick whichever the other end supports. Translation gateways can also bridge the gap when needed.
This awkward coexistence explains why adoption has been gradual rather than a clean switchover. Our article on why IPv6 adoption has been so slow looks at the practical and economic reasons in detail.
What this means for you
In day-to-day life you rarely need to think about which version you are using. Your devices, your router, and the websites you visit negotiate it for you, and many connections quietly use both. If your provider supports IPv6, some traffic already travels over it without you noticing.
Want to see the actual address your connection is using right now? The animal checkers at IP Animals will show you, and depending on your network you may see an IPv4 address, an IPv6 address, or both.
Frequently asked questions
What is the main difference between IPv4 and IPv6?
The main difference is size. IPv4 uses 32-bit addresses, giving about 4.3 billion of them, while IPv6 uses 128-bit addresses, giving a practically unlimited supply. IPv6 also simplifies routing and builds in features that were bolted on to IPv4 later.
Is IPv6 faster than IPv4?
Not dramatically in everyday use. IPv6 can be slightly more efficient because routers handle its headers more simply and it often avoids extra address translation, but for most people the speed difference is small and depends heavily on the network.
Do I need to switch to IPv6 myself?
No. Your internet provider and the websites you visit handle IPv6 support. Most modern devices and networks run IPv4 and IPv6 side by side automatically, so you rarely need to change anything.
Can IPv4 and IPv6 talk to each other directly?
Not directly. The two systems are not interoperable, so networks run both at once in what is called dual-stack, or use translation gateways to bridge between them.