IPv4 vs IPv6: What's the Difference and Why It Matters
If you've ever seen two different IP addresses when checking "what's my IP" - one short, like 86.120.45.9, and one long, like 2a02:2f0e:5a21::1 - you've already run into the difference between IPv4 and IPv6.
IPv4: the original system, but too small
IPv4 was designed in the 1980s, with room for about 4.3 billion possible addresses. That sounded generous at the time; today, with billions of phones, routers, cameras, and IoT devices online at once, the IPv4 address space has effectively run out globally. Regional registries (RIPE, ARIN, APNIC, etc.) no longer have new IPv4 blocks to hand out directly - hence the entire secondary market for buying and selling IPv4 blocks.
IPv6: the long-term fix
IPv6 was designed specifically to solve this, with an address space so large it's effectively inexhaustible for the foreseeable future. The format is longer and hexadecimal (2a02:2f0e:5a21::1a2b), which makes it less friendly to read, but it permanently solves the address shortage.
Beyond the larger space, IPv6 also simplifies some routing aspects and removes the need for NAT (address translation) in many scenarios - each device can have its own unique public address.
Why you often have both at once
Most modern connections are dual-stack: your device gets both an IPv4 and an IPv6 address simultaneously, and your operating system automatically picks which one to use for each connection, depending on what the server on the other end supports. That's why an IP detection tool might show you both addresses - it's not an error, it's normal.
On IPMeu you can check your main address, and if you want to force an IPv4-only check (useful when your connection defaults to IPv6), we have a dedicated subdomain just for that.
Practical issues caused by dual-stack
Sometimes a site or game behaves oddly because it prefers IPv6, but your network has IPv6 misconfigured (through a router or VPN, for example). The result: slow or failed connections, even though IPv4 works fine. If you run into this, the first troubleshooting step is to check which addresses you're actually assigned and temporarily disable IPv6 in your router settings to test.
In short
- IPv4 - short format, exhausted address space, still mostly used through NAT.
- IPv6 - long format, practically unlimited address space, steadily growing adoption.
- Most connections today have both at the same time (dual-stack).