IPv4 was designed in the early 1980s with 32-bit addresses — about 4.3 billion possible combinations. That sounded like a lot, but the growth of the internet exhausted the pool. Techniques like NAT (sharing one public IP among many devices) delayed the problem but did not solve it.
IPv6 uses 128-bit addresses, providing roughly 340 undecillion addresses. IPv6 also simplifies routing, has no broadcast, and makes NAT unnecessary in most cases.
IPv6 addresses look like 2001:db8::1. The double colon (::) compresses a run of zero groups. In 2026, most major networks and content providers are IPv6-ready, but a large fraction of consumer connections still use IPv4 or a dual-stack combination.