Blackjack, also known as Twenty-one or Vingt-et-un (French: “twenty-one”), is the most widely played casino banking game in the world. Blackjack is a comparing card game between a player and dealer and played with one or more French decks of 52 cards.
The player is dealt an initial two card hand with the option of drawing cards to bring the total value to 21 or less without exceeding it, so that the dealer will lose by having a lesser hand than the player or by exceeding 21. Many rule variations of blackjack exist. Since the 1960s, blackjack has been a high profile target of advantage players, particularly card counters, who track the profile of cards yet to be dealt, and adapt their wager and playing strategy accordingly.
Each blackjack game has a “basic strategy”, which is the way of playing a hand with any total value against any dealer upcard which will lose least money to the house in the long term with strictly average luck.
The bulk of basic strategy is common to all blackjack games, with most rule variations calling for changes in only a few situations. For example, if the above game used the hit soft 17 rule, common in Las Vegas Strip casinos, only 5 cells of the table would need to be changed: double on 11 vs. A, double on A/7 vs. 2, double on A/8 vs. 6 and surrender 15 or 17 vs. A.
Estimates of the house edge for blackjack games quoted by casinos and gaming regulators are generally based on the assumption that the players follow basic strategy and do not systematically change their bet size. Most blackjack games have a house edge of between 0.5% and 1%, making blackjack the cheapest casino table game. Casino promotions such as complimentary matchplay vouchers or 2:1 blackjack payouts allow the player to acquire an advantage without deviating from basic strategy.