The Algorithm and Operation System of Slot Machines — 2021 Update

Jan 30, 2021 Artyom Ustinov
How do online slots work? This question can appear in a player’s mind when deciding which casino to choose to play. This is quite logical since the work of slot machines is surrounded by various myths, for example, that playing at a certain time increases the chances of winning. In order to dispel them and generally enhance the credibility of your online casino, it is useful to know how online slots actually work. The present article is meant to clarify this issue.


Before the Internet era, slot machines were electromechanical and featured a special braking system as well as sensors that analyzed the combination to befall.

Later electromechanical devices were replaced by electric ones. They had an electric built-in engine, so players no longer had to pull the handle to play. However, sensors followed the old principle of work.

Now physical slot machines are computerized, and certain combinations occur at the expense of Random Number Generator or RNG. The same system is also used in online slots.

What is Random Number Generator (RNG)

Random Number Generator is a program that works by a certain algorithm and determines which combination will appear on the screen. This is an absolutely random process whose result neither the casino operator, nor the player or the creator of the game can know.

Even though the progress advanced a lot since the first gaming devices were tailored, the principles and reliability of Random Number Generator remain unchanged. The mechanism is regularly updated taking into account the features of modern gaming software.

Mathematicians, programmers and even psychologists took part in the creation of Random Number Generator, and similar generators have existed for a long time due to their time-proven reliability.

The generator used today is the project of a professor at the Massachusetts Institute of Technology which represents a 128-bit md5 algorithm. It is used not only in online slots, but also in security systems and personal computers.

Can RNG be trusted?

On the Internet, one can find programs that can supposedly foresee future combinations, but in fact they do not work. What such programs can actually do is steal players’ data, so you’d better avoid them.

Do not abstain from testing software. All responsible game manufacturers adopt the tactics of providing software for testing to well-known and reliable laboratories: iTech Labs, eCOGRA, GLI and NMi. Software passes serious tests during which any manipulation is excluded. This means that it is safe to play slots that have passed such a check:

  • iTech Labs
  • eCOGRA
  • GLI
  • NMi

The software is going through serious check, during which the use of any manipulations is prevented, so that it would be safe to say playing slots is reliable.

RNG logics

The first thing to note is that slot mechanisms have no memory. The computer does not know whether the player has won or lost, whether he started playing 5 minutes ago or has played for several hours. All combinations are determined by mathematical algorithms.

It is important that game results are not planned or “logical”: they are just a sequence of combinations. A person might win two jackpots almost in a row, although this might look implausible. However, this is unlikely because the number of possible combinations generated by the program is huge and each consists of 32 hex characters.

When a player starts a game, the mechanism gives out one hundred random numbers per minute which make a certain combination. The numbers selected by the generator at the time of the button click determine the characters to appear on the screen. Thus, the only way a player can “influence” the outcome of a game is to choose the time to press the button. In fact, it is pure luck. When the result appears on the screen, the system immediately calculates how much the player has won or lost and updates the information on his balance. During free spins and bonus rounds the same principle applies.

2020 Update

Even in 2020, scientists and researchers are looking for new ways to update the RNG. One of the newest methods comes from a paper written by professor David Zuckerman and Eshan Chattopadhyay published in 2015; it involves combining two ‘weak’ sources to generate a single high-quality random number.

Not only will this method enable us to implement ‘natural’ randomness to the RNG, but it will also use a lot less processing power, allowing the equipment of poorer quality to achieve better results.

2021 Update

In 2021, we can expect to see a further rise of cryptocurrency gambling worldwide. One of the biggest advantages that blockchain technology brought to the casino world is provably fair gambling. It runs on a special algorithm in slots that lets players see how the outcome of the spin came to be and verify that the operator did not tamper with it in any way. This is extremely important for slots which remain the most widely played casino game.


So far, the logics of online slots is based on the fact that there is no logic. Random Number Generator is called so due to random chances of winning and the frequency of the winnings depending on the rules of a particular game, which can be learned from the operator.

Artyom Ustinov

Artyom is Head of White Label & Turnkey Solutions and has been working in complex B2B/B2C sales, as well as business development and management consulting in iGaming for more than 10 years.

Together with the Key Account Management Team, he has helped over 100 start-ups and experienced gaming companies to launch their projects with SoftGamings.

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