A cracker consists of a segmented cardboard tube wrapped in a brightly decorated twist of paper with a prize in the middle, making it resemble an oversized sweet-wrapper. The cracker is pulled apart by two people, each holding an outer chamber, causing the cracker to split unevenly and leaving one person holding the central chamber and prize. The split is accompanied by a mild bang or snapping sound produced by the effect of friction on a shock-sensitive, chemically impregnated card strip (similar to that used in a cap gun). One chemical used for the friction strip is silver fulminate.
Assembled crackers are typically sold in boxes of three to twelve. These typically have different designs usually with red, green, and gold colours. Making crackers from scratch using tissue paper and the tubes from toilet rolls is a common activity for children.
Crackers are typically pulled at the Christmas dinner table or at parties. In one version of the cracker tradition, the person with the larger portion of cracker empties the contents from the tube and keeps them. In another, each person has their own cracker and keeps its contents regardless of whose end they were in. Typically these contents are a coloured paper hat, a small toy, a small plastic model or other trinket, and a motto, a joke, a riddle or piece of trivia on a small strip of paper. The paper hats, with the appearance of crowns, are usually worn when eating Christmas dinner. The tradition of wearing festive hats is believed to date back to Roman times and the Saturnalia celebrations, which also involved decorative headgear.
Christmas crackers are also associated with Knut's parties, held in Sweden at the end of the Christmas season.