IPv4 vs IPv6: What's the Difference?
IPv4 and IPv6 are the two versions of the Internet Protocol that give devices their addresses. Here is what changed, why the internet is moving to IPv6, and how to test your own connection.
IPv4 is the original protocol, using 32-bit addresses like 192.168.1.1 — about 4.3 billion possible addresses. IPv6 is the modern replacement, using 128-bit addresses like 2001:db8::1, which provides an effectively unlimited number of addresses. The world is moving to IPv6 because IPv4 simply ran out of room.
IPv4 vs IPv6 at a glance
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address size | 32-bit | 128-bit |
| Format | Four numbers, e.g. 192.168.1.1 | Eight hex groups, e.g. 2001:db8::1 |
| Number of addresses | ~4.3 billion | ~340 undecillion (effectively unlimited) |
| NAT needed | Yes (to share one public IP) | No (every device can have its own) |
| Security | Optional (IPsec) | Built-in (IPsec) |
| Configuration | Manual or DHCP | Automatic (SLAAC) |
Why the world is moving to IPv6
IPv4 was designed in the early 1980s, when nobody imagined billions of connected devices. It can only represent about 4.3 billion unique addresses — and the world has far more devices than that. The pool of IPv4 addresses is exhausted, which is why providers reuse them and why many homes share a single public IP through NAT.
IPv6 solves this with a 128-bit address space. There are so many IPv6 addresses that every device on Earth could have billions of its own. It also brings practical benefits: no NAT, automatic configuration, built-in security, and more efficient routing.
Reading an IPv6 address
IPv6 addresses look intimidating but follow simple rules. A full address has eight groups of four hex digits:
2001:0db8:0000:0000:0000:ff00:0042:8329
Two shortcuts make them shorter. Leading zeros in a group can be dropped, and one long run of zeros can be replaced with :::
2001:db8::ff00:42:8329
If you ever need to expand or compress an IPv6 address, the IPChecks IPv6 Expander and IPv6 Compressor do it for you.
Dual-stack: running both at once
Most modern connections are dual-stack — they have both an IPv4 and an IPv6 address and use whichever the destination supports. This is how the internet transitions gradually: IPv6 is added alongside IPv4, not instead of it. If a site only supports IPv4, your connection falls back to IPv4 automatically.
Do you have IPv6? Find out now
Run the IPChecks IPv6 Test to see whether your connection has IPv6 and whether it is working correctly.
Run IPv6 Test →Frequently asked questions
What is the difference between IPv4 and IPv6?
IPv4 is the older protocol that uses 32-bit addresses like 192.168.1.1 and offers about 4.3 billion addresses. IPv6 is the newer protocol that uses 128-bit addresses like 2001:db8::1 and offers an effectively unlimited number of addresses. IPv6 also has built-in security and more efficient routing.
Why is the internet moving to IPv6?
The world ran out of IPv4 addresses. IPv4 can only represent about 4.3 billion unique addresses, which is not enough for the billions of devices now online. IPv6 provides a vastly larger address space so every device can have its own public address.
Do I have IPv6?
Use the IPChecks IPv6 Test. It checks whether your connection has an IPv6 address and whether it is working (dual-stack). Many modern connections have both IPv4 and IPv6.
Is IPv6 faster than IPv4?
IPv6 can be slightly faster in some cases because it has more efficient routing and no need for NAT, but in practice the difference is usually small. The main benefit of IPv6 is the larger address space, not speed.
Can I use IPv4 and IPv6 at the same time?
Yes. Most modern connections are dual-stack, meaning they have both an IPv4 and an IPv6 address and use whichever is available. This is the standard way the internet is transitioning to IPv6.