Card counting is a mathematical strategy used primarily in blackjack to determine the probability of favorable outcomes by tracking the ratio of high to low cards remaining in the deck. The technique emerged in the 1960s when Edward Thorp published "Beat the Dealer," demonstrating that the house edge could be overcome through systematic card tracking. This revolutionary approach transformed blackjack from a pure chance game into one where mathematical skill could provide an advantage.
The basic premise of card counting rests on the principle that casinos use multiple decks and that cards dealt cannot be replayed. By monitoring which cards have been dealt, a skilled player can estimate the composition of remaining cards and adjust their betting strategy accordingly. High cards (10s, face cards, and Aces) favor the player in blackjack, while low cards (2-6) favor the dealer. Card counters maintain a "running count" that increases when low cards are dealt and decreases when high cards appear.