A nibble is a four-bit aggregation, or half an octet, in computing. It's sometimes referred to as a half-byte or a tetrade. The nibble is also known as a semi-octet, quadbit, or quartet in networking and telecommunications. A nibble can have up to twenty-four (24) different values. A hex digit is a single hexadecimal digit (0–F) that can be used to represent a nibble.

When chatting to a programmer at Los Alamos Scientific Laboratory in 1958, David B. Benson, a professor emeritus at Washington State University, remembers using the phrase nibble as 'half a byte' and the amount of storage necessary to keep a binary-coded decimal digit. As observed in early 1980s editorials of Kilobaud and Byte, the alternate spelling nybble mirrors the spelling of byte. The term nybble was first used in 1977 by Citibank'sconsumer-banking technology group. It developed a pre-ISO 8583 transactional communication standard using the NABBLE basic informational unit between cash machines and Citibank's data centers.

The nibble is a term used to indicate the amount of memory utilized by an IBM mainframe to retain a digit of a number written in packed decimal format (BCD). This method is used to speed up computations and make debugging easier. A single 8-bit byte is divided in half, with each nibble storing one decimal digit. The variable's last (rightmost) nibble is set aside for the sign. As a result, a variable that can store up to nine numbers is 'packed' into five bytes.