RNG - Random Number Generator

Anyone who truly wants to understand how an online casino works has to begin by understanding the basic workings of the Random Number Generator or RNG.

We usually think of the RNG as the technology that runs slot machines.  That’s true but tells only a part of the story.  The original slot machines were entirely mechanical.  The players pulled the “arm” and the reels spun until they ran out of strength and stopped. 

A Non-Physical Microchip

Modern slot machines run on vastly more complex technology.  When we “spin” the reels of the slot game, we activate a microchip that spins the reels until it decides to stop.  That’s what makes the RNG random.  In slots, the RNG doesn’t actually choose a number; it chooses a random moment to stop.

Land based casinos, in theory, do not need slots that are run by a RNG.  Since the casino itself is a physical entity, there is no reason not to have a physical machine running the popular slots games.  However, online casinos cannot exist without an RNG.  Since the online casino is not physical in the same sense that the term physical has meant for the past many millennia, it needs a non-physical means to determine the outcomes of every game.  This is the RNG.

Land based casinos have long known that people felt that their slots were somehow not on the up and up so they embraced the RNG run video slots that were first developed for online casinos.


There are a specific number of symbols and characters on a video slots machine’s reels.  There is a much larger number of “numbers” or stops that the RNG reads.  When you push “spin” in theory, the RNG follows your command and determines the result of that spin.  The casino can set the payout rate for its slots and the “hit” rate as well but the RNG decides where the reels stop on each spin.

For that reason, a slots game can go for a long time with few big hits and then it might have a run of hits in a short time.  Conversely, it could simply follow the predetermined hit rate and payout rates and show no skewed pattern of hits and misses.

The RNG Never Rests

The RNG is always at work just as the inner workings of a computer are always working as long as the computer is on.  Since someone somewhere is always playing any given slot at all times, the RNG is working all the time.  It’s as if you catch a ride on the permanent vehicle that is the RNG every time you spin the reels.

Let’s see how the RNG works in one specific type of slots game: progressive slots.  The RNG continuously runs all the combinations at very high speed.  That means that the combination for winning the progressive jackpot comes up within the RNG very often but the chances that you or any other player will win the jackpot are fairly long simply because you have to press “spin” at the exact millisecond from which moment the jackpot winning combination is destined to come up.

Ironically, it can happen that the jackpot winning combination will land soon after it has already been won by someone somewhere in the world.  It’s all a matter of hitting “spin” at the exact right moment divided into milliseconds or less.

Other Casino Games

At a land based casino, the craps, poker, roulette, blackjack, and baccarat tables are all entirely physical.  Bingo and keno have their little corners and are also physical games.  Only video poker and slots run on a RNG.

At an online casino, all the games mentioned above and all other games not mentioned are run by the RNG.  That is why when we talk about gaming strategy, we mean only the games that require thought and analysis.  These are generally poker, video poker, and blackjack.  Strategy in these games refers to making the best decisions based entirely on statistics.  The RNG decides the way the cards will fall.

The reason blackjack and video poker are so player friendly—since the house’s edge may be less than 1%—is because statistics can tell us what the best paly is at any given moment.  In an online blackjack game, when you deliberate on your next move even for a few seconds, you and you alone have determined the next card because the RNG continues to run through all the available cards.  However, since you can’t see into the RNG, you have no idea when it is the best moment to make your decision.  That’s why deliberation in the analytical games is so important.  It is the only way you can lower the house’s edge to near zero.

In roulette, it true both that 0 and 00 might come up much more frequently than the players would like or much less frequently than the house would like.  Neither has any functional control over the frequency of the times the ball lands in 0 or 00.

Payback Rate

This is the percentage of all money wagered that will make its way back to players at the end of time.  The house can calibrate the RNG to return any percentage to players.  Online casinos normally set return to player rates at about 96-97%. 

In some games, especially slots, the majority of the money returned to payers comes in big wins, either as jackpots or as big wins in the bonus rounds.  It is still luck that determines who will win the most money in any gaming session.  Slots players who play progressive slots need to know that the majority of money returned to players will come from the jackpots.

Players should decide beforehand whether they want to play a game not only with a high return to player rate but also the frequency with which money is calibrated to be returned to players.

Land based casino’s set the RNG in their digital games lower than online casinos do because land based casinos are so much more expensive to run.

Bottom Line

No system outside of statistical analysis can work in a casino game that is run by a RNG.