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How Slots Work – What is the RNG Mechanic?

  • Written By Kevin Parker
  • Edited
  • Reading 7 minutes

Online casinos are without a doubt one of the hottest trends in entertainment right now. It might have taken us nearly two decades to get here but it has certainly been worth it.

When looking at the history of online gambling, one of the verticals that always comes to mind is the slots games that are a staple on nearly all gambling platforms and spaces.

[slots are] responsible for up to over half of all gambling revenue …

In fact, they have been proven to be responsible for up to over half of all gambling revenue which essentially makes them the most popular type of casino game on the planet.

Even so, when slot lovers fire up their favorite slot machines either online or at retail spaces, they do not necessarily have what goes on behind the scenes in mind.

Enjoying these games does not require explicit knowledge about the technologies that make them possible but it is important to acknowledge their role in bringing us so much fun, joy and, sometimes, huge wins.

The Conception: Early Slot Machines and How They Worked

Slots were first conceptualized towards the end of the 19th century and for a better part of the next century, they remained unchanged – or did they?

In reality, while slot players may have noticed only subtle changes on their end, the technology that powers slot machines changed tremendously since the game was invented.

early slot machines liberty bell
One of the first Slot machines was called the Liberty Bell

The first slot machines, otherwise known as classic machines – such as the Liberty Bell and Operator Bell, made use of some rather intricate gear and lever systems. There was a shaft at the center of the machine which connected to the reels and in turn lead to a handle that players could interact with.

To get started, a player has to insert a coin. There is a coin detector for this job – it releases the braking system when the coin is detected. The handle triggers the movement of the machine and the included braking system brings it back to a stop after which other equally intricate sensors detect and communicate the position of the machine’s reels to the payout system. All this is random and not predetermined.

The Arrival of Modern Slots

Unlike classic slot machines which were entirely mechanical, modern slots are essentially electrical machines. Instead of using mechanical levers and gears, the electrical slot machines used solenoids (electromagnetic coils) to activate the stoppers. The even more modern slot machines use software to do all that.

Still, as interesting as the working mechanism of the entire machine may be, there is one thing that every gambler is usually interested in knowing.

Modern slot machines
Enter the digital stage for slots!

That is, how does a gaming machine decide whether you win or lose?

Gambling is mostly about luck, or probability, and maybe a tiny bit of skill. Slot machines are clearly the most popular luck-based games which makes them one of the areas where randomness is needed most.

Enter the Random Number Generator (RNG) Mechanics

In modern slot machines, Random Number Generators (RNGs) are used to ensure that the outcome of any casino game you are playing is essentially random.

Now, all online casinos offering slot games assure their customer that they are using the best RNGs in the industry. However, it is easy to dismiss this as the usual gambling tech jargon. Well, knowing about them is not critical for one to enjoy the games, but it is very important especially for people who are playing with real money and are very concerned about fairness.

How RNG’s Work

Now that we have established that RNGs are simply software that determines the outcome of online slot games and other online casino games, we can dive a little deeper.

All casinos have RNGs built into the online gaming platforms and games making them a critical component of the gaming experience. In essence, an RNG is a computational device or software that is tasked with generating random symbols in slot machines.

How does RNG work Mathematical
How does Random Number Generators work in Slot machines

The generation of these random numbers is in itself separate from the game as it happens even when the game is not being played. Since it operates round the clock, all it has to do is supply the slot game with the symbols or numbers it has generated.

All this is made possible through complex mathematical formulas and algorithms. On reputable online casinos, the software is audited regularly to ensure the operators do not tamper with them in order to get an edge.

Besides, they never have to do that because the math is usually working in their favor to some extent and it is extremely difficult to make RNGs generate predetermined outcomes.

[this is why slots are] the most popular type of casino game on the planet….

Furthermore, it is important to note that Random Number Generators work independently, and this is what makes the reel-spinning experience fair. That means that your previous wins or losses will not affect your next game.

The Types of RNGs In Use Today

Slot machines and several other sectors that require randomized data have benefitted immensely from advancements in RNG technology. All these applications require tremendous amounts of random numbers or symbols and this has led to improvements in the computational techniques used to generate them.

As it stands, in your reel spinning endeavors you are likely to have come across either of two types of RNGs. These are:

Pseudo-RNGs (PRNGs)

This is a type of RNG that is entirely based on software. That is, they make use of mathematical algorithms to generate random numbers. In this case, a value known as a ‘seed’ is required to kick things off. This is perhaps its most notable flaw but it is still quite sufficient for most applications.

Check our minute based pseudo number generator below:


True RNGs (TRNGs)

Unlike PRNG’s these True Random Number Generators do not need to seed values. Instead, they make use of digital snapshots of natural noises such as those from a semi-conductor or a resistor. No algorithm determines its operations. In other words, they are non-deterministic which makes them perfect for slot machines.

For slot machine lovers, you can rest assured that the slot games you will have access to are an improvement over previous versions. All the reputable gaming operators have certified RNGs that are tamper-proof.

Thankfully, there are several organizations that are dedicated to auditing and certifying the RNGs used on gaming sites so as to ensure customers are treated fairly.

Some of the most reputable companies in this regard include:

So long as the site you are playing online slots on has any of these certifications you can be sure that the RNG that determines the outcome of your games is fair. Most operators will have seals or certifications from these companies on the sites so you should keep an eye out for them.

Can You Beat a Random Number Generator?

In all honesty, as mentioned above, the chances of getting a random number generator (RNG) to produce a predetermined outcome is quite the task. It is, in fact, much easier to acknowledge that it is impossible.

However online gambling operators provide little incentives as required by law and ethics to ensure that the players get to enjoy the gaming experience while at the same time maximizing profitability. These are determined are related to:

Return to Player (RTP)

This is the theoretical amount of money that the slot machine needs to return to the players – this does not refer to individual players but the casino’s customers as a collective. It is basically what the lucky players get to win.

Hit Rate

This refers to the frequency of spins that result in a win. Games or casinos with higher hit rate percentages, therefore, be the most attractive to players.

That is all you need to get started. There is no clear-cut strategy that will assure you of a win but the uncertainty is what makes slot machines so thrilling and exciting to play.

Kevin was raised on sports since a young teen and following a (fortunate) injury pursued new hobbies in table games such as Blackjack and Poker. Since 2009 Kevin has been writing for casino sites for various big names in the industry and CasinoSites.us is but one of his latest passion projects.