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What is a Random Number Generator (RNG) and is it really the key to a fair game?

A Random Number Generator (RNG) is the engine that drives the vast majority of online casino games. Every spin of a slot machine, shuffle of a virtual deck, and any other gameplay outcome is almost always determined by an RNG algorithm. This article investigates what an RNG is, how it works, and the importance of the RNG in giving players a fair gaming experience.

What is a Random Number Generator (RNG)?

A Random Number Generator is simply a computer program designed to generate numbers that do not form a pattern. Simple RNG programs have been in existence for decades, but as the years have gone by, the algorithms used by an RNG have become increasingly effective at generating unpredictable numbers. Online casinos today seek Random Number Generators that offer the most statistically sound, normally distributed outcomes possible.

How does an RNG work?

To understand how a modern online casino’s Random Number Generator works, it helps to consider how real live table games work. In roulette, the croupier spins the wheel and launches the ball in the opposite direction along the wheel track. The properties of motion cause the ball to eventually slow to a stop, and gravity pulls the ball into one of the pockets on the wheel.


If a player or croupier could analyze every tiny detail of the ball and the wheel, monitor even the slightest irregularities that would change the ball’s trajectory, and analyze that information with the proper formulas, they could know exactly where the ball would land each time. But because this kind of analysis is impossible, there is no way of knowing which pocket the ball will finish in after each spin. The game is effectively random as a result.

The same principle is in play with online casino games powered by a Random Number Generator. The RNG simply takes a number (known as the ‘seed’) and runs it through a complex series of formulas to generate an outcome. This seed is usually time: specifically, the fraction of a second at which the player initiated the game round. If that seed was used again, the exact same result would occur. But because the casino can never know the exact moment the player will begin the next round, and because the player does not know the randomization algorithm, the games are effectively random.

Are all Random Number Generators fair?

Most online casinos use a Random Number Generator that provides players with unbiased outcomes. However, there are still a few on the market that have been shown to be unfair and cheat players out of their money.

Independent audits are the primary means by which online casinos and software developers can show players that their games are fair. Auditing companies conduct millions of tests on the games to verify that outcomes are normally distributed in the long run, do not have unusual patterns, and are consistent with the expected returns for each game. A faulty RNG designed to scam players would cause the games to fail at least one of these tests.

Some newer casinos (particularly Bitcoin casinos) choose instead to use provably fair technology. This allows players to know for certain that the games are fair and can save online casinos money on auditing costs. However, not all sites that claim to be provably fair really are. More information about RNG audits and provably fair can be found in the article, “How can I be sure the casino odds are fair?

Is the RNG the most important part of getting a fair game?

Even if the RNG is genuine, online casinos could still technically deliver unfair outcomes to players by altering the games themselves. As a simple example, a dishonest virtual blackjack game could be designed to ‘draw seconds’. The blackjack game could be programmed to draw a card, and if it was advantageous to the player, be told to ignore that card and draw a second one instead. This would put the odds heavily in favour of the casino. 

However, reputable auditing companies would be able to detect this by testing, and such a cheat would simply be impossible in any real provably fair system. Ultimately, all well-known software platforms have been tested more than enough times to show that they offer a fair game.

As years of complaints show, it is far more common for online casinos to cheat players by simply not paying them when they do win. Players should use resources like the AskGamblers casino reviews to choose sites that have a history of paying players fairly and without hesitation.

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