Blackjack is one of the most widely played casino games in the world. Also known as twenty-one, it is a card game that compares the hand values of the dealer and one or more players. While it is not known where the game originated, there do exist references to similar games as far back as the seventeenth century. The goal of the game is to reach as close to a point value of 21 as possible, without going over. Players that go over, or bust, automatically lose. Winners are determined by comparing each player hand to the dealer's hand, with each player hand able to win or lose against the dealer independent of the others. Hand values are determined by adding up the point values of each card in the hand. Face cards count as ten points, while number cards use their number value. Aces count as either 1 or 11, whichever is more beneficial to the hand. A hand that consists of an ace and a card with a point value of 10 is called a blackjack, and beats any other hand except another blackjack.


Blackjack is played with at least one standard deck of 52 cards, though in casinos up to eight decks may be shuffled together. A dealer starts by dealing a card, face up, to each player, starting with the player to the dealer's right, including the dealer. A second face up card is dealt to each player to complete their initial hands, and the dealer receives a second card face down as well. Starting from the player to the dealer's right, each player then takes a turn, where they can choose a number of actions. Players may either hit, stand, surrender or double down. If a player's first two cards are the same, players may also choose to split.


When all players are done, the dealer then may hit or stand, depending on the rules set by the casino. If the dealer busts, all players who did not previously bust automatically win. Each player's hand is then compared to the dealer's hand, with the higher value winning the round. In the case of a tie, the round is considered a “push” and the player's wager is typically returned. On each player's turn, they may choose to hit, stand, double down or surrender, or if the conditions are met, they may split. Players may audibly declare their choice, or use hand signals that are generally accepted in most casinos. Hand signals take priority over verbal instructions, and disputes with dealer actions will consider hand signals over other forms. If a player hits, another card is dealt to that player, increasing the value of the hand by the point value of the added card.


If the total is not 21 or the player does not bust, the player may choose to hit again or stand. Players may either scrape their cards on the table if holding their hand, or if the hand is on the table, may wave hand towards themselves or tap the table to declare a hit. A player who stands or stays chooses to keep their current hand and accept no more cards. The next player then takes their turn. If holding the hand, players may slide cards under their chips to denote a stand, or if cards are face up on the table, may wave their hand horizontally. A double down is only available as a choice for the player's first action. This increases the bet by one hundred percent, and the player is dealt one more card. The player is then forced to stand on their current hand. The action for this is to place additional chips to match the current bet beside the original bet, then to point with one finger.


A player may choose to split if the first two cards in the hand have the same value. This splits the two cards into two separate hands, and the player must place additional chips equal to the original wager so that each hand has the same bet amount. The dealer then deals one additional card to each new hand, and the player plays each hand separately from the other. In the case of a split, however, blackjacks are usually treated as non-blackjack 21's. Players may signal this choice by placing additional chips beside the original bet, and pointing with two fingers in a V. A surrender is available only as the first choice in a hand, and is not a valid choice in all casinos. The house takes half the player's bet and returns the rest, and the hand is no longer played. There is no recognized hand signal to surrender.


Players place their bets before the cards are dealt, a sign that they desire to play this round. While the size of the table limits the number of players, casinos typically allow others watching the game to also place their bets on any player's hand. A winning hand receives a payout equivalent to the size of the bet, though in some casinos blackjacks are paid higher. As with most other games, casino tables have a minimum and maximum bet, and as mentioned previously, may allow players to surrender instead of continue play with their hand. Many casinos also allow side bets, which are placed in designated areas. Insurance is a commonly accepted side bet offered by most casinos as well. The option is made available to players when the dealer's face up card is an ace, and is a wager that the dealer has a blackjack. It pays 2:1, and the player is typically allowed to wager up to half the value of their original bet.