The internet runs on IP addresses, but there are two versions in use today: IPv4 and IPv6. Understanding the difference matters because the internet is actively transitioning between them.
IPv4 (Internet Protocol version 4) has been the backbone of the internet since 1983. An IPv4 address looks like this:
It consists of four numbers (0–255) separated by dots. IPv4 can support approximately 4.3 billion unique addresses — a number that seemed enormous in 1983 but is now exhausted given the billions of devices connected to the internet today.
IPv6 (Internet Protocol version 6) was developed to solve the address exhaustion problem. An IPv6 address looks like this:
It uses 128-bit addresses written in hexadecimal, which allows for approximately 340 undecillion addresses (that's 340 followed by 36 zeros). In practical terms, IPv6 will never run out.
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address length | 32-bit | 128-bit |
| Total addresses | ~4.3 billion | ~340 undecillion |
| Format | 192.168.1.1 | 2001:db8::1 |
| Status | Exhausted | Active rollout |
| NAT required | Often yes | No |
| Security | Optional (IPSec) | Built-in (IPSec) |
The transition is happening but slowly. Billions of devices, routers, and systems were built around IPv4 and can't simply be upgraded overnight. Most ISPs and websites support both protocols simultaneously — a setup called dual-stack. When you connect to a modern website, your device and the server negotiate which version to use.
Many modern ISPs now assign IPv6 addresses alongside IPv4. Whether you have one depends on your ISP and router. You can check your current IP address — including whether you have an IPv6 — on our home page.