Editing Blackjack (section)

==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:<ref name="wizardofodds.com">{{Cite web |title=4-Deck to 8-Deck Blackjack Strategy - Wizard of Odds |url=http://wizardofodds.com/games/blackjack/strategy/4-decks/ |access-date=30 April 2014 |publisher=Wizard of Odds Consulting, Inc}}</ref> 
* 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

{| border="1" class="wikitable" style="text-align:center;margin:1em auto;"
|-
! rowspan="2" | Player hand
! colspan="10" | Dealer's face-up card
|-
| 2
| 3
| 4
| 5
| 6
| 7
| 8
| 9
| 10
| A
|-
! colspan="11" | Hard totals (excluding pairs)
|-
! 18–21
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
|-
! 17
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:white; color:black" | Us
|-
! 16
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:white; color:black" | Uh
| style="background:white; color:black" | Uh
| style="background:white; color:black" | Uh
|-
! 15
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:white; color:black" | Uh
| style="background:white; color:black" | Uh
|-
! 13–14
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-

! 12
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! 11
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
|-
! 10
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! 9
| style="background:lime; color:black" | H
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! 5–8
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! colspan="11" | Soft totals
|-
|
| 2
| 3
| 4
| 5
| 6
| 7
| 8
| 9
| 10
| A
|-
! A,9
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
|-
! A,8
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:cyan; color:black" | Ds
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
|-
! A,7
| style="background:cyan; color:black" | Ds
| style="background:cyan; color:black" | Ds
| style="background:cyan; color:black" | Ds
| style="background:cyan; color:black" | Ds
| style="background:cyan; color:black" | Ds
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! A,6
| style="background:lime; color:black" | H
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! A,4–A,5
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! A,2–A,3
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! A,A{{efn|group=nb|For the specific circumstance where the player has a pair of aces and is forbidden to split but permitted to hit.}}
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:cyan; color:black" | Dh
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! colspan="11" | Pairs
|-
|
| 2
| 3
| 4
| 5
| 6
| 7
| 8
| 9
| 10
| A
|-
! A, A
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
|-
! 10,10
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
| style="background:red; color:black" | S
|-
! 9,9
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:red; color:black" | S
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:red; color:black" | S
| style="background:red; color:black" | S
|-
! 8,8
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:white; color:black" | Usp
|-
! 7,7
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! 6,6
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! 5,5
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:cyan; color:black" | Dh
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! 4,4
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|-
! 2,2–3,3
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:yellow; color:black" | SP
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
| style="background:lime; color:black" | H
|}

Key:
:<span style="background:red; color:black">'''S'''</span> = Stand
:<span style="background:lime; color:black">'''H'''</span> = Hit
:<span style="background:cyan; color:black">'''Dh'''</span> = Double (if not allowed, then hit)
:<span style="background:cyan; color:black">'''Ds'''</span> = Double (if not allowed, then stand)
:<span style="background:yellow; color:black">'''SP'''</span> = Split
:<span style="background:white; color:black">'''Uh'''</span> = Surrender (if not allowed, then hit)
:<span style="background:white; color:black">'''Us'''</span> = Surrender (if not allowed, then stand)
:<span style="background:white; color:black">'''Usp'''</span> = 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.<ref name="wizardofodds.com" />

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.<ref>{{Cite web |year=2021 |title=How to Win at Blackjack – Strategies 2021 |url=https://veritop.com/casino-games/blackjack/strategies |url-status=live |archive-url=https://web.archive.org/web/20210513010325/https://veritop.com/casino-games/blackjack/strategies |archive-date=May 13, 2021 |website=Veritop}}</ref>

===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:<ref name="wizard">{{Cite web |title=The Wizard of Odds |url=http://wizardofodds.com/blackjack/appendix3c.html |access-date=December 8, 2006 |website=Fine points of basic strategy in single-deck blackjack}}</ref>
* 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 0.04%, which falls to 0.003% for a six-deck game.<ref name="wizard2">{{Cite web |title=The Wizard of Odds |url=http://wizardofodds.com/blackjack/appendix15.html |access-date=December 19, 2006 |website=Total Dependent and Composition Dependent Basic Strategy in Blackjack}}</ref>

===Advantage play===
{{Main|Advantage player}}
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, making advantage players unwanted customers for casinos. Advantage play can lead to ejection or [[Black Book (gambling)|blacklisting]]. Some advantageous play techniques in blackjack include:

====Card counting====
{{Main|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 around 0.5–1% when players use basic strategy.<ref>{{Cite web |title=Blackjack - Beating Bonuses |url=http://www.beatingbonuses.com/blackjack.htm#table |website=beatingbonuses.com}}</ref> Card counting can give the player an edge of up to about 2%.<ref name="TOB">{{Cite book |last=Griffin |first=Peter |title=The theory of blackjack: the compleat card counter's guide to the casino game of 21 |date=March 1, 1999 |publisher=Huntington Press |isbn=978-0929712130 |edition=6th}}</ref>{{rp|5}}

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,<ref name="TOB" />{{rp|6–7}} 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.<ref>{{Cite book |last=Thorp |first=Edward O. |url=https://www.worldcat.org/oclc/655875 |title=Beat the dealer: a winning strategy for the game of twenty-one: a scientific analysis of the world-wide game known variously as blackjack, twenty-one, vingt-et-un, pontoon, or van-john |date=1966 |publisher=Random House |isbn=0-394-70310-3 |edition=revised |location=New York |pages=132–136 |oclc=655875}}</ref> The use of external devices to assist in card counting is illegal in [[Nevada]].

====Shuffle tracking====
{{main|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.<ref>{{Cite web |title=Blackjack in Color |url=http://www.blackjackincolor.com/Shuffletracking2.htm |website=Shuffle Tracking Counts}}</ref>

[[Arnold Snyder|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.<ref>{{Cite book |last=Roberts |first=Stanley |url=https://www.worldcat.org/oclc/12568192 |title=The Gambling Times guide to blackjack |publisher=Gambling Times |year=1984 |isbn=0-89746-015-4 |editor-last=Thorp |editor-first=Edward O. |location=Hollywood |oclc=12568192}}</ref><ref>{{Cite book |last=Patterson |first=Jerry L. |url=https://www.worldcat.org/oclc/13395266 |title=Break the dealer : winning strategies for today's blackjack |date=1986 |publisher=Putnam |others=Eddie Olsen |isbn=0-399-51233-0 |location=New York, NY |page=83 |oclc=13395266}}</ref><ref>{{Cite book |last=Patterson |first=Jerry L. |url=https://www.worldcat.org/oclc/21444382 |title=Blackjack, a winner's handbook |date=1990 |publisher=Perigee Books |isbn=0-399-51598-4 |edition=Completely rev. and updated |location=New York, NY |page=51 |oclc=21444382}}</ref>

====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.<ref>{{Cite book |last=Sfetcu |first=Nicolae |title=Play Blackjack |publisher=Nicolae Sfetcu |year=2014 |pages=20}}</ref>