History
Blackjack's immediate precursor was the English version of '' twenty-one'' called ''Vingt-Un'', a game of unknown (but likely Spanish) provenance. The first written reference is found in a book by the Spanish author Miguel de Cervantes. Cervantes was aRules of play at casinos
At a blackjack table, the dealer faces five to nine playing positions from behind a semicircular table. Between one and eightPlayer decisions
After the initial two cards, the player has up to five options: "hit", "stand", "double down", "split", or "surrender". Each option has a corresponding hand signal. * Hit: Take another card. : ''Signal'': Scrape cards against the table (in handheld games); tap the table with a finger or wave a hand toward the body (in games dealt face up). * Stand: Take no more cards; also known as "stand pat", "sit", "stick", or "stay". : ''Signal'': Slide cards under chips (in handheld games); wave hand horizontally (in games dealt face up). * Double down: Increase the initial bet by 100% and take exactly one more card. The additional bet is placed next to the original bet. Some games permit the player to increase the bet by amounts smaller than 100% which is known as "double for less." Non-controlling players may or may not double their wager, but they still only take one card. : ''Signal'': Place additional chips beside the original bet outside the betting box and point with one finger. * Split: Create two hands from a starting hand where both cards are the same value. Each new hand gets another card so that the player has two starting hands. This requires an additional bet on the second hand. The two hands are played out independently, and the wager on each hand is won or lost independently. In the case of cards worth 10 points, some casinos only allow splitting when the cards rank the same. For example, 10-10 could be split, but K-10 could not. Doubling and re-splitting after splitting are often restricted. A 10-valued card and an ace resulting from a split usually isn't considered a blackjack. Hitting split aces is often not allowed. Non-controlling players can opt to put up a second bet or not. If they do not, they only get paid or lose on one of the two post-split hands. : ''Signal'': Place additional chips next to the original bet outside the betting box and point with two fingers spread into a V formation. * Surrender: Forfeit half the bet and end the hand immediately. This option is only available at some tables in some casinos, and the option is only available as the first decision. : ''Signal'': Spoken; there are no standard signals. Hand signals help the " eye in the sky" make a video recording of the table, which resolves disputes and identifies dealer mistakes. It is also used to protect the casino against dealers who steal chips or players who cheat. Recordings can also identifyInsurance
If the dealer shows an ace, an "insurance" bet is allowed. Insurance is a side bet that the dealer has a blackjack. The dealer asks for insurance bets before the first player plays. Insurance bets of up to half the player's current bet are placed on the "insurance bar" above the player's cards. If the dealer has a blackjack, insurance pays 2 to 1. In most casinos, the dealer looks at the down card and pays off or takes the insurance bet immediately. In other casinos, the payoff waits until the end of the play. In face-down games, if a player has more than one hand, they can look at all their hands before deciding. This is the only condition where a player can look at multiple hands. Players with blackjack can also take insurance. Insurance bets lose money in the long run. The dealer has a blackjack less than one-third of the time. In some games, players can also take insurance when a 10-valued card shows, but the dealer has an ace in the hole less than one-tenth of the time. The insurance bet is susceptible to advantage play. It is advantageous to make an insurance bet whenever the hole card has more than a one in three chance of being a ten. Card counting techniques can identify such situations.Rule variations and effects on house edge
''Note: where changes in the house edge due to changes in the rules are stated in percentage terms, the difference is usually stated here in percentage points, not a percentage. For example, if an edge of 10% is reduced to 9%, it is reduced by one percentage point, not reduced by ten percent.'' Blackjack rules are generally set by regulations that establish permissible rule variations at the casino's discretion. Blackjack comes with a "house edge"; the casino's statistical advantage is built into the game. Most of the house's edge comes from the fact that the player loses when both the player and dealer bust. Blackjack players using basic strategy lose on average less than 1% of their action over the long run, giving blackjack one of the lowest edges in the casino. The house edge for games where blackjack pays 6 to 5 instead of 3 to 2 increases by about 1.4%, though. Player deviations from basic strategy also increase the house edge. ;Dealer hits soft 17 Each game has a rule about whether the dealer must hit or stand on soft 17, which is generally printed on the table surface. The variation where the dealer must hit soft 17 is abbreviated "H17" in blackjack literature, with "S17" used for the stand-on-soft-17 variation. Substituting an "H17" rule with an "S17" rule in a game benefits the player, decreasing the house edge by about 0.2%. ;Number of decks All things being equal, using fewer decks decreases the house edge. This mainly reflects an increased likelihood of player blackjack, since if the player draws a ten on their first card, the subsequent probability of drawing an ace is higher with fewer decks. It also reflects the decreased likelihood of a blackjack-blackjack push in a game with fewer decks. Casinos generally compensate by tightening other rules in games with fewer decks, to preserve the house edge or discourage play altogether. When offering single-deck blackjack games, casinos are more likely to disallow doubling on soft hands or after splitting, restrict resplitting, require higher minimum bets, and to pay the player less than 3:2 for a winning blackjack. The following table illustrates the mathematical effect on the house edge of the number of decks, by considering games with various deck counts under the following ruleset: double after split allowed, resplit to four hands allowed, no hitting split aces, no surrendering, double on any two cards, original bets only lost on dealer blackjack, dealer hits soft 17, and cut-card used. The increase in house edge per unit increase in the number of decks is most dramatic when comparing the single-deck game to the two-deck game, and becomes progressively smaller as more decks are added. ;Late/early surrender: Surrender, for those games that allow it, is usually not permitted against a dealer blackjack; if the dealer's first card is an ace or ten, the hole card is checked to make sure there is no blackjack before surrender is offered. This rule protocol is consequently known as "late" surrender. The alternative, "early" surrender, gives the player the option to surrender ''before'' the dealer checks for blackjack, or in a no-hole card game. Early surrender is much more favorable to the player than late surrender. For late surrender, however, while it is tempting to opt for surrender on any hand which will probably lose, the correct strategy is to only surrender on the very worst hands, because having even a one-in-four chance of winning the full bet is better than losing half the bet and pushing the other half, as entailed by surrendering. ;Resplitting: If the cards of a post-split hand have the same value, most games allow the player to split again, or "resplit". The player places a further wager, and the dealer separates the new pair dealing a further card to each as before. Some games allow unlimited resplitting, while others may limit it to a certain number of hands, such as four hands (for example, "resplit to 4"). ;Hit/resplit split aces: After splitting aces, the common rule is that only one card will be dealt to each ace; the player cannot split, double, or take another hit on either hand. Rule variants include allowing resplitting aces or allowing the player to hit split aces. Games allowing aces to be resplit are not uncommon, but those allowing the player to hit split aces are extremely rare. Allowing the player to hit hands resulting from split aces reduces the house edge by about 0.13%; allowing resplitting of aces reduces the house edge by about 0.03%. Note that a ten-value card dealt on a split ace (or vice versa) will not be counted as a blackjack but as a soft 21. ;No double after split: After a split, most games allow doubling down on the new two-card hands. Disallowing doubling after a split increases the house edge by about 0.12%. ;Double on 9/10/11 or 10/11 only: Under the "Blackjack strategy
Basic strategy
Each blackjack game has a basic strategy, the optimal method of playing any hand. When using basic strategy, the long-term house advantage (the expected loss of the player) is minimized. An example of a basic strategy is shown in the table below, which applies to a game with the following specifications: * Four to eight decks * The dealer hits on a soft 17 * A double is allowed after a split * Only original bets are lost on dealer blackjack Key: :S = Stand :H = Hit :Dh = Double (if not allowed, then hit) :Ds = Double (if not allowed, then stand) :SP = Split :Uh = Surrender (if not allowed, then hit) :Us = Surrender (if not allowed, then stand) :Usp = Surrender (if not allowed, then split) Most basic strategy decisions are the same for all blackjack games. Rule variations call for changes in only a few situations. For example, to use the table above on a game with the stand-on soft 17 rule (which favors the player, and is typically found only at higher-limit tables today) only 6 cells would need to be changed: hit on 11 ''vs.'' A, hit on 15 ''vs.'' A, stand on 17 ''vs.'' A, stand on A,7 ''vs.'' 2, stand on A,8 ''vs.'' 6, and split on 8,8 ''vs.'' A. Regardless of the specific rule variations, taking insurance or "even money" is never the correct play under a basic strategy. Estimates of the house edge for blackjack games quoted by casinos and gaming regulators are based on the assumption that the players follow basic strategy. Most blackjack games have a house edge of between 0.5% and 1%, placing blackjack among the cheapest casino table games for the player. Casino promotions such as complimentary matchplay vouchers or 2:1 blackjack payouts allow players to acquire an advantage without deviating from basic strategy.Composition-dependent strategy
The basic strategy is based on a player's point total and the dealer's visible card. Players can sometimes improve on this decision by considering the composition of their hand, not just the point total. For example, players should ordinarily stand when holding 12 against a dealer 4. But in a single deck game, players should hit if their 12 consists of a 10 and a 2. The presence of a 10 in the player's hand has two consequences: * It makes the player's 12 a worse hand to stand on (since the only way to avoid losing is for the dealer to go bust, which is less likely if there are fewer 10s left in the shoe). * It makes hitting safer, since the only way of going bust is to draw a 10, and this is less likely with a 10 already in the hand. Even when basic and composition-dependent strategies lead to different actions, the difference in expected reward is small, and it becomes smaller with more decks. Using a composition-dependent strategy rather than a basic strategy in a single-deck game reduces the house edge by 4 in 10,000, which falls to 3 in 100,000 for a six-deck game.Advantage play
Blackjack has been a high-profile target for advantage players since the 1960s. Advantage play attempts to win more using skills such as memory, computation, and observation. While these techniques are legal, they can give players a mathematical edge in the game, taking advantage of players' unwanted customers for casinos. Advantage play can lead to ejection or blacklisting. Some advantageous play techniques in blackjack include:Card counting
During the course of a blackjack shoe, the dealer exposes the dealt cards. Players can infer from their accounting of the exposed cards which cards remain. These inferences can be used in the following ways: * Players can make larger bets when they have an advantage. For example, the players can increase the starting bet if many aces and tens are left in the deck, in the hope of hitting a blackjack. * Players can deviate from basic strategy according to the composition of their undealt cards. For example, with many tens left in the deck, players might double down in more situations since there is a better chance of getting a good hand. A card counting system assigns a point score to each card rank (e.g., 1 point for 2–6, 0 points for 7–9, and −1 point for 10–A). When a card is exposed, a counter adds the score of that card to a running total, the 'count'. A card counter uses this count to make betting and playing decisions. The count starts at 0 for a freshly shuffled deck for "balanced" counting systems. Unbalanced counts are often started at a value that depends on the number of decks used in the game. Blackjack's house edge is usually between 0.5%–1% when players use basic strategy. Card counting can give the player a house edge over up to minus 2%. Card counting works best when a few cards remain. This makes single-deck games better for counters. As a result, casinos are more likely to insist that players do not reveal their cards to one another in single-deck games. In games with more decks, casinos limit penetration by ending the shoe and reshuffling when one or more decks remain undealt. Casinos also sometimes use a shuffling machine to reintroduce the cards whenever a deck has been played. Card counting is legal unless the counter is using an external device, but a casino might inform counters that they are no longer welcome to play blackjack. Sometimes a casino might ban a card counter from the property. The use of external devices to help count cards is illegal throughout the United States.Shuffle tracking
Another advantage play technique, mainly applicable in multi-deck games, involves tracking groups of cards (also known as slugs, clumps, or packs) through the shuffle and then playing and betting according to when those cards come into play from a new shoe. Shuffle tracking requires excellent eyesight and powers of visual estimation but is harder to detect; shuffle trackers' actions are largely unrelated to the composition of the cards in the shoe. Arnold Snyder's articles in '' Blackjack Forum'' magazine brought shuffle tracking to the general public. His book, ''The Shuffle Tracker's Cookbook'', mathematically analyzed the player edge available from shuffle tracking based on the actual size of the tracked slug. Jerry L. Patterson also developed and published a shuffle-tracking method for tracking favorable clumps of cards and cutting them into play and tracking unfavorable clumps of cards and cutting them out of play.Identifying concealed cards
The player can also gain an advantage by identifying cards from distinctive wear markings on their backs, or by hole carding (observing during the dealing process the front of a card dealt face down). These methods are generally legal although their status in particular jurisdictions may vary.Side bets
Many blackjack tables offer side bets on various outcomes including: *Player hand and dealer's up card total 19, 20, or 21 ("Lucky Lucky") *Player initial hand is a pair ("Perfect pairs") *Player initial hand is suited, suited, and connected, or a suited K-Q ("Royal match") *Player initial hand plus dealer's card makes a flush, straight, or three-of-a-kind poker hand ("21+3") *Player initial hand totals 20 ("Lucky Ladies") *Dealer upcard is in between the value of the player's two cards ("In Bet") *First card drawn to the dealer will result in a dealer bust ("Bust It!") *One or both of the player's cards is the same as the dealer's card ("Match the Dealer") The side wager is typically placed in a designated area next to the box for the main wager. A player wishing to wager on a side bet usually must place a wager on blackjack. Some games require that the blackjack wager should equal or exceed any side bet wager. A non-controlling player of a blackjack hand is usually permitted to place a side bet regardless of whether the controlling player does so. The house edge for side bets is generally higher than for the blackjack game itself. Nonetheless, side bets can be susceptible to card counting. A side count designed specifically for a particular side bet can improve the player's edge. Only a few side bets, like "Insurance" and "Lucky Ladies", offer a sufficient win rate to justify the effort of advantage play. In team play, it is common for team members to be dedicated to only counting a side bet using a specialized count.Blackjack tournaments
Blackjack can be played in tournament form. Players start with an equal number of chips; the goal is to finish among the top chip holders. Depending on the number of competitors, tournaments may be held over several rounds, with one or two players qualifying from each table after a set number of deals to meet the qualifiers from the other tables in the next round. Another tournament format, Elimination Blackjack, drops the lowest-stacked player from the table at pre-determined points in the tournament. A good strategy for blackjack tournaments can differ from a non-tournament strategy because of the added dimension of choosing the amount to be wagered. As in poker tournaments, players pay the casino an initial entry fee to participate in a tournament, and re-buys are sometimes permitted.Video blackjack
Some casinos, as well as general betting outlets, provide blackjack among a selection of casino-style games at electronic consoles. Video blackjack game rules are generally more favorable to the house; e.g., paying out only even money for winning blackjacks. Video and online blackjack games generally deal each round from a fresh shoe (i.e., use an RNG for each deal), rendering card counting ineffective in most situations.Variants and related games
Blackjack is a member of the family of traditional card games played recreationally worldwide. Most of these games have not been adapted for casino play. Furthermore, the casino game development industry actively produces blackjack variants, most of which are ultimately not adopted by casinos. The following are the most prominent and established variants in casinos. * Spanish 21 provides players with liberal 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 21s, 6–7–8 21s, 7–7–7 21s, late surrender, and player blackjacks and player 21s always winning. The trade-off is having no 10s in the deck, although the jacks, queens, and kings are still there. An unlicensed version of Spanish 21 played without a hole card is found in Australian casinos under the name "Pontoon". *21st-Century Blackjack (or "Vegas Style" Blackjack) is found in California card rooms. In variations, a player bust does not always result in an automatic loss; depending on the casino, the player can still push if the dealer also busts. The dealer has to bust with a higher total, though. * Double Exposure Blackjack deals the first two cards of the dealer's hand face up. Blackjacks pay even money, and players lose on ties. Also, players can neither buy insurance nor surrender. * Double Attack Blackjack has 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. * Blackjack Switch is played over two hands, and the second card can be switched between hands. For example, if the player is dealt 10–6 and 5–10, 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. *Blackjack Hall of Fame
In 2002, professional gamblers worldwide were invited to nominate great blackjack players for admission into the Blackjack Hall of Fame. Seven members were inducted in 2002, with new people inducted every year after. The Hall of Fame is at the Barona Casino inReferences
Further reading
General literature
* * * * Parlett, David (1990). ''A History of Card Games'', OUP, Oxford.Blackjack literature
* ''Beat the Dealer: A Winning Strategy for the Game of Twenty-One'', Edward O. Thorp, 1966, * ''Blackbelt in Blackjack'', Arnold Snyder, 1998 (1980), * ''Blackjack and the Law'', I. Nelson Rose and Robert A. Loeb, 1998, * ''Blackjack: A Winner's Handbook'', Jerry L. Patterson, 2001, (1978), * ''Encyclopedia of Casino Twenty-One'', Michael Dalton, 2016, (1993), * ''Ken Uston on Blackjack'', Ken Uston, 1986, * ''Knock-Out Blackjack'', Olaf Vancura and Ken Fuchs, 1998, * ''Million Dollar Blackjack'', Ken Uston, 1994 (1981), * ''Playing Blackjack as a Business'',Mathematics of blackjack
* ''Luck, Logic, and White Lies: The Mathematics of Games'', Jörg Bewersdorff, 2004, , , 121–134, online supplementExternal links
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