Typically, blackjack is played using one to eight decks of standard playing cards, with most casinos favoring multiple decks for various reasons. Single-deck games are less common and often found in specific venues, while multi-deck games, such as those using six or eight decks, are prevalent in many casinos. The use of multiple decks can make card counting more difficult for players, increasing the house edge. The specific number of decks used can vary based on the casino's house rules and the particular variation of blackjack being played.