Blackjack one of the most popular casino card games in the world. The popularity of blackjack is due to a mix of chance with elements of skill and the publicity that surrounds card counting. Blackjacks predecessor was vingt-et-un (twenty-one) which originated in French casinos around 1700 and did not off the 3:2 bonus for a two-card 21.

Blackjack when first introduced to the US was not very popular so gambling houses tried offering various bonus payouts to get the players to the tables. One such bonus was a 10 to 1 payout if the player's hand consisted of the ace of spades and a black jack (either the jack of clubs or spades). This hand was called blackjack and the name stuck to the game even thought the bonus payout was soon abolished. The way the game is currently played a "blackjack" may not necessarily contain a jack or any black cards at all.

Rules

Each player is dealt two cards and is then offered the opportunity to take more. The hand with the highest total wins as long as it doesn't exceed 21; a hand with a higher total than 21 is said to bust or have too many. Cards 2 through 10 are worth their face value, and face cards (jack, queen, king) are also worth 10. An ace's value is 11 unless this would cause the player to bust, in which case it is worth 1. A hand in which an ace's value is counted as 11 is called a soft hand, because it cannot be busted if the player draws another card.

The goal of each player is to beat the dealer by having the higher, unbusted hand. Note that if the player busts he loses, even if the dealer also busts (therefore Blackjack favors the dealer). If both the player and the dealer have the same point value, it is called a "push", and neither player nor dealer wins the hand. Each player has an independent game with the dealer, so it is possible for the dealer to lose to one player, but still beat the other players in the same round.

The minimum bet is printed on a sign on the table and varies from casino to casino and table to table. After initial bets are placed, the dealer deals the cards, either from one or two hand-held decks of cards, known as a "pitch" game, or more commonly from a shoe containing four or more decks. The dealer gives two cards to each player, including himself. One of the dealer's two cards is face-up so all the players can see it, and the other is face down. (The face-down card is known as the "hole card". In European blackjack, the hole card is not actually dealt until the players all play their hands.) The cards are dealt face up from a shoe, or face down if it is a pitch game.

In American blackjack, if the dealer's face-up card is an ace or a ten-value, the dealer checks his hole card to see if he has blackjack. This check occurs before any of the players play, but after they have been offered insurance (if the face-up card is an ace). If the dealer has blackjack, all players lose their initial bets, except players who also have blackjack, who push. (In some American casinos, the dealer does not actually check the hole card until after the players have all played. At that time, if the dealer turns out to have blackjack, all players who did not have blackjack lose their bets, and players who increased their bets by doubling or splitting lose only the original bet, and have the additional bets returned to them; thus, the end result is precisely as if the dealer had checked the hole card before playing.)

A two-card hand of 21 (an ace plus a ten-value card) is called a "blackjack" or a "natural", and is an automatic winner (unless the dealer has blackjack as well, in which case the hand is a push). A player with a natural is usually paid 3:2 on his bet. Some casinos pay only 6:5 on blackjacks; although this reduced payout has generally been restricted to single-deck games where card counting would otherwise be a viable strategy. The move was decried by longtime blackjack players.

The player's options for playing his or her hand are: Hit: Take another card. Stand: Take no more cards. Double down: Double the wager, take exactly one more card, and then stand. Split: Double the wager and have each card be the first card in a new hand. This option is available only when both cards have the same value. Surrender: Forfeit half the bet and give up the hand. Surrender was common during the early- and mid-20th century, but is no longer offered at most casinos.

The player's turn is over after deciding to stand, doubling down to take a single card, or busting. If the player busts, he or she loses the bet even if the dealer goes on to bust.

After all the players have finished making their decisions, the dealer then reveals his or her hidden hole card and plays the hand. House rules say that the dealer must hit until he or she has at least 17, regardless of what the players have. In some casinos a dealer must also hit a soft 17 (a combination of cards adding up to either 7 or 17, such as an ace and a 6).

If the dealer busts then all remaining players win. Bets are normally paid out at the odds of 1:1. Players who push (tie) with the dealer receive their original bet back.

Some common rules variations include:

Each blackjack variation has its own set of rules, strategies and odds. It is advised to take a look at the rules of the specific variation before playing. Many countries have legal acts and laws, which determine how a casino game of Blackjack must be played.

Insurance

If the dealer's upcard is an Ace, the player is offered the option of taking Insurance before the dealer checks his 'hole card'.

The player who wishes to take Insurance can bet an amount up to half his original bet. The Insurance bet is placed separately on a special portion of the table, which usually carries the words "Insurance Pays 2:1". The player who is taking Insurance is betting that the dealer was dealt a natural, i.e. a two-card 21 (a blackjack), and this bet by the player pays off 2:1 if it wins. It is called insurance since if the dealer has a blackjack, the bet wins the same amount of the player's Blackjack wager, such that if insurance is taken and the player doesn't have blackjack but dealer does, no money is lost. Of course the dealer can end up not having blackjack and the player can still win or lose the blackjack bet.

Insurance is a bad bet for the non-counting player who has no knowledge of the hole card because it has a house edge of 2 to 15%, depending on number of decks used and visible 10-cards. Essentially, taking insurance amounts to betting that the dealer's hole card is a ten or face card. Since in an infinite deck, 4/13 of the cards are tens or face cards, an unbiased insurance wager would actually pay 9:4, or 2.25:1; since the bet only pays 2:1, the house has a strong advantage. However, if the player has been counting cards, he may know that more than a third of the deck is ten-value cards, in which case insurance becomes a good bet.

If a player has a natural (an ace and a ten or face-card) and the dealer is showing an ace, the dealer usually asks the player "Even money?" instead of offering insurance. If the player accepts the offer, he is immediately paid 1:1 for his natural, regardless of whether the dealer has blackjack. Thus, accepting "even money" has exactly the same payout as buying insurance: if the dealer does not have blackjack, the player would forfeit the insurance bet and win 3:2 on the natural, thus receiving a net payout equal to the original bet; if the dealer does have blackjack, the player would push on the natural and win 2:1 on the insurance wager, again receiving a net payout equal to the original bet. Since taking "even money" is equivalent to buying insurance, it is likewise a bad choice for the player, unless he has been counting cards and knows the deck has an unusually high proportion of ten-value cards.

In casinos where a hole card is dealt, a dealer who is showing a card with a value of Ace or 10 may slide the corner of his or her facedown card over a small mirror or electronic sensor on the tabletop in order to check whether he has a natural. This practice minimizes the risk of inadvertently revealing the hole card, which would give the sharp-eyed player a considerable advantage.

Variants

Pontoon is an English variation of Blackjack with large rule and strategy differences. In Australia, however, Pontoon is exactly the same as the American game Spanish 21 but played without a hole card.

Spanish 21 provides players with many liberal blackjack rules, such as doubling down any number of cards (with the option to 'rescue', or surrender only one wager to the house), payout bonuses for five or more card 21's, 6-7-8 21's, 7-7-7 21's, late surrender, and player blackjacks always winning and player 21's always winning, at the cost of having no 10 cards in the deck (though there are jacks, queens, and kings).

21st Century Blackjack (also known as "Vegas Style" Blackjack) is commonly found in many California card rooms. In this form of the game, a player bust does not always result in an automatic loss; there are a handful of situations where the player can still push if the dealer busts as well, provided that the dealer busts with a higher total.

Certain rules changes are employed to create new variant games. These changes, while attracting the novice player, actually increase the house edge in these games. Double Exposure Blackjack is a variant in which the dealer's cards are both face-up. This game increases house edge by paying even money on blackjacks and players losing ties. Double Attack Blackjack has very liberal blackjack rules and the option of increasing one's wager after seeing the dealer's up card. This game is dealt from a Spanish shoe, and blackjacks only pay even money.

The French and German variant "Vingt-et-un" (Twenty-one) and "Siebzehn und Vier" (Seventeen and Four) don't include splitting. An ace can only count as eleven, but two aces count as a Blackjack. This variant is seldom found in casinos, but in private circles and barracks.

Chinese Blackjack is played by many in Asia, having no splitting of cards, but with other card combination regulations.

Another variant is Blackjack Switch, a version of blackjack in which a player is dealt two hands and is allowed to switch cards. For example, if the player is dealt 10-6 and 10-5, then the player can switch two cards to make hands of 10-10 and 6-5. Natural blackjacks are paid 1:1 instead of the standard 3:2, and a dealer 22 is a push.

Recently, thanks to the popularity of poker, Elimination Blackjack has begun to gain a following. Elimination Blackjack is a tournament format of blackjack.

Many casinos offer optional side bets at standard blackjack tables. For example, one common side-bet is "Royal Match", in which the player is paid if his first two cards are in the same suit, and receives a higher payout if they are a suited queen and king (and a jackpot payout if both the player and the dealer have a suited queen-king hand). These side bets invariably offer worse odds than well-played blackjack.