Cracking is a broad term that refers to any process that results in the breaking down of larger hydrocarbon molecules into smaller molecules.

Most of the major conversion units in a refinery perform some type of cracking.

Cracking can be achieved through the use of heat (thermal cracking) or hydrogen addition (hydrocracking), often in the presence of a catalyst (catalytic cracking/hydrocracking).

Cracking in its various forms is the primary means of improving the product yield of a refinery to include more of the high-value light products and less of the low value heavy products.