'''Edge sorting''' is a technique used in [[advantage gambling]] where a player determines whether a face-down [[playing card]] is likely to be low or high at [[casino]] table games by observing and exploiting subtle unintentional differences on the backs of some types of card, after persuading a croupier to cooperate by unwittingly sorting the cards into low and high.<ref>{{cite web|url=http://www.ibtimes.com/what-edge-sorting-phil-ivey-sued-borgata-casino-allegedly-cheated-win-96-million-baccarat-1571442 |title=What Is Edge Sorting? Phil Ivey Sued By Borgata Casino, Allegedly Cheated To Win $9.6 Million In Baccarat |publisher=[[International Business Times]] |author=Thomas Barrabi |date=2014-04-14 |accessdate=2014-04-19}}</ref> Some packs of cards produced by some manufacturers have an unintentional regularityirregularity. Typically all the backs of the cards in such a pack are identical, but the two long edges of each card are consistently distinguishable: the pattern is not symmetrical to a 180° rotation (half a full turn). During the course of a game, a player will ask the [[Croupier|dealer]], a casino employee, to rotate some face-up cards, perhaps saying they feel it will bring them luck. The dealer does not realise that cards are being turned so that low cards, typically, 6, 7, 8, or 9 are one way round, high cards the other way round, and that the edges are different. The dealer is also asked to shuffle the cards with an automatic shuffler, which does not change the orientation as a manual shuffle may do. The dealer is not obliged to comply with these requests, but will usually do so if thought to be due to gamblers' superstition or mistrust. Over the course of a game, low cards will tend to be oriented one way, high cards the other.<ref>{{cite web|url=http://www.dailymail.co.uk/news/article-2420796/I-read-cards-Im-cheat-U-S-poker-ace-suing-Britains-oldest-casino-denied-8million-win-admits-using-controversial-edge-sorting-technique.html |title='I read the cards but I'm no cheat': U.S. poker ace suing Britain's oldest casino after being denied £8million win admits using controversial 'edge sorting' technique |publisher=[[Daily Mail]] |author=Ian Gallagher |date=2013-09-14 |accessdate=2014-04-19}}</ref> Once a significant proportion of cards have been rotated, any player who knows this can gain a statistical edge more than outweighing [[house edge]] by using the knowledge whether the card to be turned is likely to be low or high.<ref name=PAMAG>{{cite web|url=http://www.phillymag.com/news/2014/04/14/borgata-poker-star-phil-ivey-cheated-edge-sorting/ |title=Borgata: Poker Star Phil Ivey Cheated Us Out of $10 Million Using Edge Sorting |publisher=Philly Mag |author=Victor Fiorillo |date=2014-04-14 |accessdate=2014-04-19}}</ref>
A UK High Court judgement ruled that the technique, which requires the player to trick the croupier into rotating cards, is cheating in civil law, and that a casino was justified in refusing payment of winnings; this ruling would not be applicable if the player simply took advantage of an observed error or anomaly for which he was not responsible in, say, the backs of the cards.
