How slots are programmed – Are slots really random

Slot machines are the most popular games in online casinos. BetandSlots presents a closer look at how slots are programmed.

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Slot machines are the most popular games in online casinos. And in Las Vegas of course! Here e want to take a closer look at how slots are programmed. If you look at the range of casino games, you will find that the slot games area of casinos always offers the largest selection of games to play online.

We hope that in this BetandSlots article we can show you how an online slot works technically.

How slots are programmed – The random number generator

The heart of every slot machine is the so-called random number generator. This generator is part of every machine and is activated whenever you click the spin button and wish for winning money.

Each random number generator number represents a symbol on the slot machine. Depending on which combination of numbers the generator spits out when the reel stops, you see a combination of symbols. If these symbols are on the same payline, you win. If this is not the case, it is an unsuccessful spin.

The most important point on the Random Number Generator is the fact that this system has no memory or history. This means that every result of the random number generator does not depend on previous results.

Every result of the generator is therefore purely coincidental. You can compare it to the game results in roulette. Again, each game result is completely independent of the result of the previous game round.

Are slots really random

Large software manufacturers invest a lot of money to ensure that the random number generator is correctly and correctly programmed. 

These manufacturers and online casinos themselves commission external companies to test the slot machines for correct functionality and that the payback percentage is according to standards in the long run.

These third-party companies periodically test all slot machines. This ensures that the random number generator works properly and without errors in the respective mobile casino.

How slots are programmed – Probabilities of winning and RTP

However, there is a probability that a certain symbol will appear at a certain point, which can be calculated. Assuming that a slot has three reels, three rows, and three different symbols, of which only one is a winning symbol and also that there is only one winning line, the number of possible combinations on the monitor would be exactly 3x3x3, i.e. 27 be. 

Since only one combination, namely three winning symbols on a winning line, wins, the probability of winning is 1/27 = 0.037 or 3.37%.

In other words, if the game was long enough, the winning combination would appear on average in every 27th game. If the winnings were exactly 27 coins, this would also correspond to a payout ratio of 100%. 

However, as usual, the payout ratio is reduced by the so-called “House edge”, or the casino advantage. In the example, a payout of 26 euros would correspond to a payout ratio of 96.3%. This number is the RTP, meaning Return To Player.

Another option would be to insert zero profit symbols or symbols with a very low value. Most of these are the well-known playing card symbols or the lemons in the “fruit” machines.

What should I do if I think a slot machine is incorrectly programmed?

While it is unlikely, a slot machine may malfunction. If you are affected by such a malfunction, it is important that slots players act correctly.

First of all, while playing slot you should take a screenshot of the game the moment the malfunction occurred. With this screenshot, you should then contact the customer service of the online casino operator immediately. 

Here you have the so-called log files of each spin available and the casino can understand whether it is actually a bug in the game.

Such a scenario is rather unlikely, but if it does occur, the most important thing is that you have a screenshot of the malfunction, otherwise it can be difficult to prove this malfunction.

How slots are programmed – Slot variants

The slot machines have the modern 3D video slots with some very many paylines, classic slots such as the “fruit” and “diamond” slots and the so-called jackpots. 

But video poker, as well as table and card games, are fundamentally not programmed differently, only that additional rules of the game sometimes apply. In video poker, if the game is skillful and there is a paytable that fits the perfect game, payout ratios of over 100% are possible.

Many slots also have so-called gamble features. There is a chance to double, triple or even quintuple a win by playing another 50:50 game with guessing cards or colors. So-called multipliers, multiply your winnings, are also in the latest slot machines versions. In addition, many slots have a free spin mode, in which players can make winnings without straining their own bankroll when spinning.

Other games, including progressive jackpots, where the amount of the jackpot increases, the more players play the game also have bonus rounds. If several bonus symbols appear, there is a chance within the bonus rounds to achieve high winnings or even hit the jackpot.

The best-known game programmers include NetEnt, Novomatic, Merkur, Microgaming, Evolution, Yggdrasil, Bally or PLAY’n GO, etc.


Of course, there are many different types of slot machines. Some have five reels and 100 paylines and some have only three reels and five paylines. In principle, however, all slot machines work the same.

The center of every slot machine is the so-called random number generator. This always determines when you click the spin button the outcome of the game and whether you win in a game round or not.

It is also important to be aware that a previous game round cannot influence the outcome of the next shoot. It is therefore completely irrelevant whether you won or lost in the previous shoots. Your chances of winning are always the same.

We hope that this article has given you an understanding of how slot machines are programmed. Now it is up to you whether you are lucky and become a slot winner at the numerous slot machines in the various online casinos.

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