Understanding How Online Slots Work Before Playing

If you go to any online casino, you will quickly discover that online slots are by far the most popular casino game. How could you have known? When compared to other types of casino games, by the sheer number of them that are available to play. Some top online casinos list thousands of different online slots versus only a few dozens of table games – a simple case of supply and demand.

In terms of how they work, the fundamentals of online slots are not much different from how they have always been. A player places his bet, spins the wheels, and waits for the reels to stop before seeing if he has won. If the reels have stopped in such a way that a line of the same symbols is visible, you will win. Of course, the more rare a symbol is, the more money a player will win.

While mechanical slot machines date back to the late 1890s, the fundamentals have always remained constant. However, the machines’ randomness was determined mechanically back then, whereas in recent years, slots have moved online and their randomness is now determined by random number generators.

Because the randomness of a slot machine will always play a large role in determining your chances of winning, it is critical for all players to have a basic understanding of how it all works. This is what we will be discussing in this article, so sit back, relax, and enjoy learning about how online slots work.

How Do Online Slot Machines Work?

When you look at an online slot, you’ll notice that it still looks like something you’d find in a local casino. They still, in general, have three to five sets of reels that spin before stopping to determine whether or not you have won. While a physical machine cannot have some of the modern features found in online slots, such as expanding wilds and animated bonus rounds, it will still function in the same manner.

As previously stated, the only difference is the method by which that outcome is determined. To ensure the randomness of their results, licensed casino game providers use RNG software that is regulated by online gambling authorities.

While the idea of a piece of software determining their outcome is unsettling for many, the fact that online casinos are required to allow their RNG to be tested by regulators as part of their license agreement should reassure them that someone is ensuring some fairness.

Random Number Generator (RNG)

So, what is RNG and how does it work? In the backend of every single online slot machine, there is software that is constantly selecting random numbers. In fact, the RNG generates thousands of numbers between 0 and 4 billion every second (approximately). For each spin, each of those numbers will be linked to a different outcome on the reels, and the number generated at the exact moment you press’spin’ will be the outcome.

To make it easier to understand, here is how a spin works:

– When a player presses the spin button, a random number is generated.

– The mathematical module in the game software converts that number and determines where the reels should stop.

– The reels stop exactly where they should, and the game computes the outcome of the spin.

– The outcome is then communicated to the player.

Because RNG software is completely random, your previous wins and losses will have no bearing on your next spin. Yes, if you had pressed the spin button a second earlier or later than you did, the outcome would have been different, but as you know, there’s no way of knowing whether you would have fared any better or worse.

So, how do casinos make a profit?

Many of you are probably wondering how an online casino makes money when its online slots are completely random. Simply put, a casino has an advantage in the long run with each and every game that it hosts for players.

Let’s pretend we’re playing a game of flipping a coin. You pay me $1 for the flip, and if you’re lucky enough to win, I’ll give you $1.50, but if you lose, I’ll take your entire bet. As you can see, you will either win $0.50 or lose $1 in each game, and while the outcome is completely random, and there is a chance that you will get extremely lucky and beat me, the odds are heavily stacked in my favor in the long run.

This is essentially how all casino games are designed, albeit in a more complicated manner. The math behind online slots ensures that, despite being completely random, the online casino will always have a slight advantage over its players in the long run. The following are just a few examples of how a slot’s math is defined:

– The number and types of symbols on the reels – The sizes of wins discovered in the paytable

– The likelihood of bonus features being activated

– Bonus feature chances and win sizes

The math behind the game will determine how much money the casino makes, not the RNG, which is completely random. Essentially, a casino will always make a profit over a long period of time. Some players will be lucky and win, while others will be unlucky and lose, but the end result for a casino is always the same.

Dispelling Popular Slot Myths

We thought it would be a good idea to dispel some of the more common misconceptions about slots now that you have a better understanding of how online slots determine their results and that they are fair and random in doing so.

Slot machines operate in cycles of wins and losses

This is completely false because each and every spin is completely random from one another. It is just as likely to win after five consecutive spins as it is to lose after five consecutive spins. You could win two large payouts in a row or go 10 spins without winning anything. You will, of course, have good and bad streaks, but this is simply due to being lucky with the complete randomness that RNG provides.

Slot machines will pay out large amounts of money and then stop paying out large amounts of money until they have recouped their losses. While this myth may have persisted due to older slot machines in casinos not having enough money inside to pay out, this is not the case with online slots that do not pay out directly to the player. In any case, the original myth about physical machines is just that: a myth. It is well known that if a machine does not have enough money, players are directed to casino staff to be reimbursed if they win on an empty machine.

Using autoplay for your spins always results in a lower payout

Some people believe that machines will take advantage of a player’s failure to look at the screen and leaving the slot to spin on its own for a set period of time by rewarding them with fewer wins. This is simply not the case because both autoplay and manual spins use the same math. Gambling regulators constantly test the RNGs in casinos and on slots to ensure that things like this do not occur.

These are just three of the many myths about slot machines and their random number generators, but there are many more. Some people don’t seem to believe that computer software can be trusted to be fair, but we can assure you that online slots are completely random and fair.

Understanding the House Edge in a Slot Machine

The first thing to realize is that no online slot is the same as another; each will have its own set of variables that will determine how likely you are to win. RTP and volatility/variance in slots are two mathematical characteristics of a slot that you should be aware of.

RTP (Return to Player)

The RTP of an online slot indicates how much money players should expect to receive from a slot after a long period of play, as well as how much of a house edge that slot has over its players.

Let’s start with a simple example. Assume an online slot has an RTP of 95% and you spend $1 billion playing it over a long period of time. With that RTP, you should expect to receive approximately $950 million in winnings. The remaining $50 million is estimated to be the profit from the slot machine. That 5% is also known as the house edge, or the advantage that the slot machine has over you in the long run.

We used such a large amount of money because RTP is calculated over such a large sample size. Initially, your first few hundred spins could yield returns ranging from 30 percent to 1000 percent. However, the longer you play, the closer you will get to the RTP figures.

This is why you should try to play slots with a high RTP because you will have a better chance of winning or minimizing your losses over time. Slots have an RTP of around 96 percent on average, but some have as high as 98 or 99 percent. Because not all slots will have their RTP declared, we recommend that you stick to those that do.


Another factor to consider is the volatility of a casino game, which is more difficult to explain. Using Roulette as an example is the simplest way to gain a basic understanding.

If you bet on red, you have a 50/50 chance of winning, but you won’t win much. According to statistics, you should win half of the time and double your bet.

On the other hand, if you bet on a single number, you will only win once in 37 tries, but you will win 36 times your bet.

So, what does this have to do with online slots?

In terms of volatility, each slot will have its own classification (otherwise known as variance). They are generally classified as low, medium, or high, with low implying that you can expect regular small wins with the occasional big win thrown in, high implying that you will not win very often but will be rewarded well when you do, and medium implying that you will be rewarded well when you do.

If you wanted our advice on which slots to play, we would always recommend high volatility slots with as high an RTP as possible. While you will not win as frequently, there is always the possibility of bringing in some game-changing wins – just a few of these will put you well ahead. Consistently winning smaller amounts never seems to get you anywhere, even if you do have a chance of eventually winning larger amounts.

Furthermore, because of the larger payouts, playing high variance slots gives you a good chance of beating the declared RTP of a slot. Imagine playing a few spins and winning a large sum of money – you could call it a day right then and there. It will take far more effort on a low variance slot because you will have to get lucky on a far more consistent basis just to gradually increase your credits. RTP will eventually triumph over long-term play.

High variance slots typically have a lower RTP to balance them out, but even with that lower RTP, it is possible to beat if you are in the right place at the right time. Just make sure to leave once you’ve found a good path ahead of you.


Online slots are the most popular type of game found at online casinos, but many players have never fully grasped how they operate. Hopefully, this article has helped you gain a better understanding of how online slots generate their results and what your chances of beating them are.

The takeaway is that online slots are completely random, and that the math behind the games will determine your chances of profiting in the long run. Forget the common myths about slots and start enjoying them for what they are: a casino game that allows you to win large sums of money but will ultimately win out against the player base over a long period of time.

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