Why the World Ran Out of IPv4 Addresses
IPv4 offers about 4.3 billion addresses, and they are gone. Here is how the internet outgrew them, what was done to cope, and why IPv6 is the real fix.
When the internet's addressing system was designed in the early 1980s, 4.3 billion addresses felt limitless. Today it is not nearly enough, and the free pool has been empty for years. Here is how that happened and what kept the internet running anyway.
How many addresses IPv4 has
IPv4 addresses are 32 bits long, which allows exactly 232 — about 4.29 billion — unique combinations. That is the number you see written as four values from 0 to 255, like 203.0.113.42. If you want a refresher on how these identifiers work, our page on what an IP address is covers the basics, and the IPv4 vs IPv6 comparison puts the two schemes side by side.
Why 4.3 billion was not enough
- The internet exploded. The designers never imagined billions of people, each carrying several connected devices — phones, laptops, watches, TVs, and smart-home gadgets.
- Early allocations were wasteful. In the internet's first decade, whole blocks of 16 million addresses were handed to single organizations, much of which was never used.
- Not every address is usable. Large ranges are reserved for private networks, multicast, and testing, shrinking the pool that can actually be assigned to the public internet.
The day the pool ran dry
The organization that hands address blocks to the world's regional registries allocated its last free IPv4 blocks in early 2011. The regional registries then depleted their own pools one by one over the following years. Since then, there has been no fresh supply — new IPv4 addresses only become available when someone gives them up, and they now trade on a secondary market for real money.
The workarounds that kept IPv4 alive
- NAT. Network Address Translation lets an entire home or office share one public IP, so your router already multiplexes all your devices behind a single address.
- Carrier-grade NAT. ISPs took the same idea further, placing many customers behind one shared public IP. That is CGNAT, and it is why the address on our home page may be shared with strangers.
- Address markets. Unused blocks are bought and sold, redistributing scarce addresses to where they are needed.
These tactics stretched IPv4 far beyond its natural limit, but they add complexity and break some direct connections, as anyone who has fought with port forwarding behind CGNAT knows.
IPv6: the actual fix
IPv6 uses 128-bit addresses, providing roughly 340 undecillion of them — a 3.4 followed by 38 zeros. That is enough to give every grain of sand on Earth billions of addresses. With IPv6, every device can have its own real public address again, no NAT trickery required. Adoption has climbed steadily and now carries a large share of traffic on major networks. Curious whether your connection is ready? Run our IPv6 test.
The bottom line
IPv4 ran out because a 1980s design met a 21st-century internet. NAT and CGNAT bought decades of extra life, but the permanent answer is IPv6 and its practically unlimited address space. For now the internet runs on both at once — you can see exactly which your connection uses on our home page.