In computing, a nibble (often spelled nybble) is 4 bits, or half an octet (an 8-bit byte). Being four bits, there are sixteen (24) possible values, so a nibble corresponds to a single hexadecimal digit (thus, it is often referred to as a "hex digit"). A full byte is represented by two hexadecimal digits; therefore, it is common to display a byte of information as two nibbles.
The term nibble originates from the fact that the term byte is a pun on the English word bite. A nibble is a small bite, or half a bite. The nybble spelling parallels the spelling of byte.
In earlier times, when computer storage was at a premium, the practice of optimizing memory at the expense of processing speed was known as nybble byting or byte nybbling.
See also
Nibbles is the name of a video game that is present on many modern mobile phones.