IPv4 and IPv6 do the same job — addressing devices on a network — but at very different scales.
Format
IPv4 uses 32 bits and is written as four decimal blocks, like 203.0.113.42. IPv6 uses 128 bits and hexadecimal in eight groups, like 2001:db8:85a3::8a2e:370:7334. The :: notation compresses runs of zeros.
Capacity
IPv4 offers roughly 4.3 billion addresses, not enough for today's device count. IPv6 offers 2^128 addresses, a number that will not run out in practice.
What changes day to day
| Aspect | IPv4 | IPv6 | | --- | --- | --- | | NAT required | Yes, on most networks | No | | Auto configuration | Via DHCP | Native SLAAC | | Fragmentation | Done by routers | Source only | | Header | Variable | Fixed and simpler |
Why am I still on IPv4
The transition is slow because it requires upgrades across providers, equipment and software. Most networks run dual-stack, with both protocols at once. If your connection has no IPv6, the IPv6 Test says so explicitly — and the reason is almost always your provider, not your computer.