IPv6 Addresses

IPv6 is the newer version of Internet Protocol (IP) addressing, and IPv4 is the older version that it replaces. An IPv6 address is 128 bits long, which gives a vastly larger supply of unique addresses than IPv4.

How an IPv6 address is written

An IPv6 address is written as eight groups of hexadecimal digits, with a colon between each group, and each group is four hex digits long. A hexadecimal digit can be 0–9 or A–F, so each digit stores 4 bits and each group stores 16 bits.

For example, 2f7a:0041:9c3d:0000:5b8e:00d2:7a10:3f66 has eight groups. Eight groups × 16 bits = 128 bits. Hexadecimal is used rather than denary because it is far more compact: one hex digit stands for 4 bits, so a group of four digits replaces 16 binary digits.

Why IPv6 was introduced

IPv4 uses 32-bit addresses, so the total number of possible IPv4 addresses is limited to about 4.3 billion (2 to the power of 32). As more phones, laptops, games consoles and other devices connect to networks, the available IPv4 addresses can run out. IPv6 has about 340 trillion trillion trillion possible addresses (2 to the power of 128), so there is plenty of room for every device to have its own unique address and for the internet to keep growing.