IPv4 and IPv6 addresses differ primarily in their address length, format, and capabilities:

• Address Length and Space : IPv4 uses a 32-bit address format, allowing for about 4.3 billion unique addresses. In contrast, IPv6 uses a 128-bit address format, providing approximately 340 undecillion (3.4×10^38) unique addresses, vastly expanding the address space to accommodate the growing number of internet-connected devices

• Address Format : IPv4 addresses are numeric and written in dot-decimal notation (e.g., 192.168.10.150), consisting of four decimal numbers separated by periods. IPv6 addresses are alphanumeric, written in colon-hexadecimal notation (e.g., 3002:0bd6:0000:0000:0000:ee00:0033:6778), consisting of eight groups of four hexadecimal digits separated by colons

• Header and Packet Structure : IPv6 has a simplified header with fewer fields (8 fields) compared to IPv4 (12 fields), which improves routing efficiency and performance. IPv6 also eliminates the checksum field present in IPv4 and handles fragmentation differently, performing it only at the sender side

• Security : IPv6 was designed with mandatory Internet Protocol Security (IPsec) support for authentication and encryption, enhancing security at the network layer. IPv4 can use IPsec, but it is optional and less commonly implemented

• Network Features : IPv6 supports auto-configuration and eliminates the need for Network Address Translation (NAT), enabling true end-to-end connectivity. It replaces IPv4’s broadcast communication with more efficient multicast and anycast transmissions. IPv6 also includes built-in Quality of Service (QoS) and improved mechanisms to prevent address spoofing and improve privacy

• Compatibility and Adoption : IPv4 is widely supported and simpler to configure, but it faces limitations due to address exhaustion. IPv6 adoption is growing, especially for new devices and networks, but it is more complex to configure and not yet universally supported by all websites and services

In summary, IPv6 addresses are longer, more complex, and designed to overcome IPv4's limitations by providing a vastly larger address space, enhanced security, and improved network efficiency