Protocol comparison
IPv4 and IPv6 do the same essential job: they address devices and carry packets between networks. The difference is in the amount of address space, the way networks are operated, and how both protocols coexist while the transition continues.
IPv4
IPv6
Address format
IPv4 uses four decimal numbers separated by dots. IPv6 uses hexadecimal groups separated by colons. A full IPv6 address has eight groups, but zeroes can be shortened, which is why addresses such as 2606:4700:4700::1111 are still manageable in logs and configuration files.
The extra address space changes how networks can be planned. A home, office, or cloud environment can receive a sizeable prefix instead of repeatedly carving a small pool of shared public IPv4 addresses into private subnets.
IPv4 address sharing
Network Address Translation lets many private IPv4 devices share one public address. It has been essential for IPv4 growth, but it also makes inbound connectivity, logging, and troubleshooting more complicated. NAT is separate from a firewall; networks still need deliberate filtering rules in either protocol.
IPv6 routing
IPv6 removes the address-exhaustion reason for NAT. A device can have a globally unique address, while firewalls still decide which traffic is allowed. In practice, providers and organizations choose the routing and security policies that fit their network.
Real-world deployment
IPv6 is not backward-compatible with IPv4 at the packet level, so one protocol cannot simply replace the other overnight. Dual-stack deployments support both. Where that is not possible, translation, proxies, or gateways provide compatibility.
For developers and operators, the practical approach is to test both address families, publish DNS records deliberately, and avoid assuming that an address contains only dots or fits into a 32-bit value.
Technical references: RFC 8200 specifies IPv6; RFC 791 specifies IPv4.