IPv6 format: eight hextets, leading-zero and :: compression, prefix length (usually /64)

IPv6 was created because IPv4's 32-bit address space ran out. An IPv6 address is 128 bits long, which gives a practically unlimited number of addresses and removes the need for NAT to conserve addresses. The 128 bits are written as eight groups of four hexadecimal digits separated by colons. Each group is 16 bits and is often called a hextet (or quartet). A full example: 2001:0db8:0000:0000:0000:ff00:0042:8329. Hexadecimal uses the digits 0 to 9 and letters a to f, and letters are case-insensitive, though lowercase is standard.