IPv4 is the current protocol for creating, assigning, and using IP addresses. IPv4 was the first widely used IP address. The Internet protocol uses a 32-bit numeric address, which means it can have about 4.3 billion IP addresses.

But when IPv4 was introduced 40 years ago, engineers had no idea that millions of people would have at least a few internet-connected devices just like us. Clearly, IPv4 cannot meet the needs of the global population. What's more, in the early days of IPv4, some big companies had allocated billions of IP addresses. They haven't used it yet, but they don't want to give it back to the world. We've run out of IP.