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Online casinos, also known as virtual casinos or Internet casinos, are online versions of traditional ("brick and mortar") casinos. Online casinos enable gamblers to play and wager on casino games through the Internet.
Online casinos generally offer odds and payback percentages that are comparable to land-based casinos. Some online casinos claim higher payback percentages for slot machine games, and some publish payout percentage audits on their websites. Assuming that the online casino is using an appropriately programmed random number generator, table games like blackjack have an established house edge. The payout percentage for these games are established by the rules of the game.
Online casino types 
Online casinos can be divided into two groups based on their interface: web-based and download-only casinos. Some casinos offer both interfaces.
Web-based online casinos 
Web-based online casinos (also known as flash casinos) are websites where users may play casino games without downloading software to the local computer. Games are mainly represented in the browser plugins Macromedia Flash, Macromedia Shockwave, or Java and require browser support for these plugins. Also, bandwidth is needed since all graphics, sounds and animations are loaded through the web via the plugin. Some online casinos also allow gameplay through a plain HTML interface. Apple devices such as iPod, iPad and iPhone cannot play Flash games as the technology is not supported.
Download-based online casinos 
Download-based online casinos require the download of the software client in order to play and wager on the casino games offered. The online casino software connects to the casino service provider and handles contact without browser support. Download-based online casinos generally run faster than web-based online casinos since the graphics and sound programs are located within the software client, rather than having to be loaded from the Internet. On the other hand, the initial download and installation of a download-based online casino client does take time. As with any download from the Internet, the risk of the program containing malware does exist. Still the graphics and sounds at download-based online casinos are most of the time much better than those at web-based online casinos.
Online casino game variants 
The game types through the online casino interface can also be divided into two categories: live casinos, which offer live interactive casino gaming via video link, and virtual casinos, which provide computer simulations of popular casino games. However, there is a great deal of crossover between the two, as most of the major virtual casinos now offer live gaming, and websites that are predominantly marketed as live casinos usually tend to offer virtual gaming in addition to live dealer games.
Virtual casino games 
In a virtual casino game, the outcome of each game is dependent on the data produced by a pseudorandom number generator (PRNG). This determines the order of the cards in card games, the outcome of a dice throw, or the results produced by the spinning of a slot machine or roulette wheel. PRNGs use a set of mathematical instructions known as an algorithm to generate a long stream of numbers that give the impression of true randomness. While this is not the same as true random number generation (computers are incapable of this without an external input source), it provides results that satisfy all but the most stringent requirements for true randomness.
When implemented correctly, a PRNG algorithm such as the Mersenne Twister will ensure that the games are both fair and unpredictable. However, the player has to take it on trust that the software has not been rigged to increase the house edge, as its inner workings are invisible to the user. Properly regulated online casinos are audited externally by independent regulators such as eCOGRA to ensure that their win percentages are in line with the stated odds, and this provides a degree of assurance to the player that the games are fair.
Live dealer casino games 
In a live casino game, a human dealer runs the game in real time from a casino gaming table, which can be seen via a live streaming video link. Players can make betting decisions via a console on their computer screen, and can communicate with the dealer using a text chat function.
The results of the physical transactions by the dealer, such as the outcome of the roulette wheel spin or the dealing of cards, are translated into data that can be utilized by the software by means of optical character recognition (OCR) technology. This enables the player to interact with the game in much the same way as they would with a virtual casino game, except for the fact that the results are determined by real-life actions rather than automated processes.
These games are a lot more expensive for websites to host than virtual games, as they involve a heavier investment in technology and staffing. A live casino studio typically employs one or more cameramen, several croupiers running the various games, an IT manager to ensure that any technical hitches are dealt with swiftly, and a pit boss that acts as an adjudicator in case of disputes between players and croupiers.
In most cases, this requires at least a three room setup, comprising a live studio, a server/software room, and an analyst’s room. The configuration of these rooms varies from casino to casino, with some having several gaming tables in one room, and some having a single table in each room.
The high running costs involved with operating live dealer games is the reason why online casinos only tend to offer a handful of the most popular games in this format, such as roulette, blackjack, sic bo, baccarat, and poker. In comparison, the running costs associated with virtual games are very low, and it is not uncommon for online casinos to offer hundreds of different virtual casino games to players on their site.
Online casinos vary in their approach to the hosting of live games, with some providing live games via their own television channel, and others offering the games exclusively via their website. In the case of televised games, players can often use their mobile phone or television remote controls to place bets instead of doing so via a computer connected to the internet.
Games offered 
A typical selection of gambling games offered at an online casino might include:
Many online casinos offer sign-up bonuses to new players making their first deposit, and often on subsequent play as well. These bonuses are a form of marketing that may incur a cost (potentially justifiable in order to attract a new player who may return and deposit many more times), since the casino is essentially giving away money in return for a commitment from the player to wager a certain minimum amount before they are allowed to withdraw. Since all casino games have a house edge, the wagering requirements ensure that the player cannot simply walk away with the casino's money immediately after claiming the bonus. These wagering requirements are commonly set to be sufficiently high that the player has a negative expectation, exactly as if they had deposited and not claimed a bonus.
Casinos may choose to restrict certain games from fulfilling the wagering requirements, either to restrict players from playing low-edge games or to restrict 'risk-free' play (betting for instance both red and black on roulette), thereby completing the wagering requirement with a guaranteed profit after the bonus is taken into account.
No deposit bonuses 
The most popular form of bonus is one that can be claimed without the need to deposit any of the player's own money - known as a no deposit bonus. These bonuses are used as acquisition tools by casinos wishing to attract new players. No deposit bonuses don't always take the form of real cash, as exemplified below.
Non-cashable bonuses 
Non-cashable bonuses may be called "sticky" or "phantom" bonuses. In both cases, the bonus forms a part of the player's balance, but cannot be cashed out. The difference comes at cashout time. A phantom bonus disappears when the player cashes out, while the sticky bonus 'sticks' to the player's account until it is lost.
Comp points 
Comps are commonly available at land-based casinos, but also exist online. Comp points can usually be exchanged for cash, prizes, or other comps. The amount of cash given per wager is usually very small and often varies with game selection. A casino might offer three comp points for each $10 wagered on slots and one comp point for each $10 wagered on blackjack. The casino might give $1 for each 100 comp points. This example is equivalent to returning 0.3% of wagers on slots and 0.1% of wagers on blackjack. In addition online casinos may offer comps such as free tickets to online tournaments, tickets to other special events, extra bonuses, souvenirs and pay back.
Bonus hunting 
Bonus hunting (also known as bonus bagging or bonus whoring) is a type of advantage gambling where turning a profit from casino, sportsbook and poker room bonus situations is mathematically possible. For example, the house edge in blackjack is roughly 0.5%. If a player is offered a $100 cashable bonus requiring $5000 in wagering on blackjack with a house edge of 0.5%, the expected loss is $25. Therefore the player has an expected gain of $75 after claiming the $100 bonus.
Bonus disputes 
A large portion of online casino disputes relate to bonuses. Casinos may label players who win using bonuses as "bonus abusers." Both players and casinos may commit fraud. An example of player fraud is creating multiple accounts and using the accounts to claim a sign-up bonus several times. An example of casino fraud is changing terms of a bonus after a player has completed the wagering requirements, then requiring the player to meet the new bonus terms.
Fraudulent online casino operator behaviour 
Fraudulent behaviour on the part of online casinos has been documented, almost exclusively by player advocacy websites and forums. The most commonly reported behaviour is a refusal to pay withdrawals to legitimate winners. An online casino with multiple confirmed cases of fraudulent behavior is often called a rogue casino by the online casino player community.
Some casino software has been mathematically proven to cheat, such as Elka System/Oyster Gaming and Casino Bar. Other examples of cheating software have been proven by leaked screenshots of the back-end administrative interface availablle only to the casino operator. For example Casino Web Scripts software allows the casino to bank a proportion of every bet placed by the player, and set the chances of winning to be higher in fun play mode than in real money play.
Many casino gambling portals and player forums maintain blacklists of rogue casinos. While some carry more authority than others, all blacklists constitute individual webmaster and player opinions rather than an official list from any type of regulating body.
Online gambling legislation often has loopholes that result from the rapid development of the technology underpinning the development of the industry. Such countries as Belgium, Canada, Finland, Sweden have state gambling monopolies and do not grant licenses to foreign casino operators. According to their law, operators licensed on the territory of these countries can only be considered legal. At the same time, they can't prosecute foreign casino operators and only block their sites. Players in these countries can't be punished and can gamble at any site they can access.
The Australian Interactive Gambling Act 2001 (IGA) criminalises the supply of online casino games by an operator anywhere in the world to persons located in Australia. It only targets operators of online gambling sites, resulting in the curious situation that it is not illegal for a player in Australia to access and gamble at an online casino. No operator has even been charged with an offence under the IGA and many online casinos accept Australian customers.
Gambling online has never been a crime in Canada, as international casino operators can provide their services to residents so long as they are regulated in their own jurisdictions. Recently, however, local gaming commissions have decided to launch their own online gambling commission, providing residents with the opportunity to play at online casinos that are regulated by their own provincial governments. The British Columbia Lottery Corporation and Loto Quebec were the first two provincial entities to launch these types of online casinos.
United States 
In the United States, the legality of online gambling is debated and can vary from state to state. The Unlawful Internet Gambling Enforcement Act of 2006 (UIGEA) limits the ability of banks and payment processors to transact with internet gambling sites that are unlawful under any federal or state law. However it does not define the legality or otherwise of an internet based gambling site. It was commonly assumed that the Federal Wire Act prohibited all forms of online gambling. However in December 2011, the United States Department of Justice released a statement clarifying that the Wire Act applied only to sports betting sites and not to online casinos, poker, or lottery sites, leaving the definition of legality up to individual states. Certain states such as Nevada, Delaware, and New Jersey have started the process of legalising and regulating online gambling and it is expected that regulation will continue on a state by state basis.
See also 
- Roulette.co.uk: Understanding Random Number Generation
- Liveroulette.co.uk: Live Dealer Casinos, how the technology works
- WizardOfOdds.com Ask The Wizard May 8, 2002
- Wizard of Odds.com glossary See "sticky bonus" and "phantom bonus"
- eCOGRA Casino Dispute Report
- Casinomeister's Rogue Pit
- Casinobar evidence by Michael Shackleford
- Casino Web Scripts evidence at Casino Listings forum.
- WizardofOdds.com: Blacklist
- Cowie, Tom. "Last Bets: around the world in online casinos — first stop, Gibraltar". Crikey.
- Gaming Act
- Controversial New Gambling Legislation
- Canadian Gambling Insight Infographic
- Vardi, Nathan. "Department Of Justice Flip-Flops On Internet Gambling". Forbes.
- 888 Legal online casino in Nevada