How Slots Work

Slots are without a doubt the most popular game genre in the online gambling industry. With dozens of software providers hard at work creating new titles for us to enjoy and with thousands of games already available, maybe it is a good idea to take a more comprehensive look at how they actually work. Slots may be fun to play and simple enough for anyone to enjoy, but do not let looks deceive you. There are many factors to take into consideration in any given slot and in this article, we will cover all important bases on how slots work.

History of Slots

History of SlotsThe history of slots is not as long as other traditional casino games like blackjack, roulette or baccarat, but it is no less important. The first record of a slot machine dates back to the late 19th century, developed in New York. It featured 50 different card faces, 5 reels and worked more what we now know as video poker. The machine was placed in bars and it did not pay out money, rather rewards came in the form of what the establishment had to offer, for example, drinks, cigars, etc.

A few years later, Charles Fey created in San Francisco what we now know as a slot machine. Unlike its predecessor, this version of the game came with only 3 reels and it did away with the poker cards, adding in their place five unique symbols. It was done so that an easy and convenient payout system may be designed, a task which proved impossible with the poker machine. The new machine was called ‘Liberty Bell’, named after one of the five symbols.

Over the years, slot machines become more advanced and more complex to design. It wasn’t until the 1970s when the first video slot games were created and after being approved by the Nevada State Gambling Commission, they become a real hit in casinos all over Las Vegas. Of course, with the rise of the Internet, also came online gambling and the slot format carried over perfectly in the new online casinos. Nowadays, we have thousands of unique and memorable slots at our disposal and fans of the genre will have a great time exploring all the different titles.

How Slots Work

Slots rngMany people are under the impression that slots gaming is a simple concept. After all, you pull down a level or press a button, the reels spin and you see whether you win or lose. Granted, this does sound incredibly simple, but there are important factors to consider when playing slots. Before you can actually get down to exploring the genre, you should have a rough idea of how the game works and what are the driving forces behind it.

Whereas once fruit machines were entirely mechanical, modern day slots are software-based and the visuals serve only to be pleasing to the player. As soon as you press the button, the game decides whether you win or lose. This is done via RNG (Random Number Generation) systems embedded in the core of the game. Every time that you place a bet, the game generates a bunch of numbers which signify whether the spin was a winning one. This process is entirely up to chance and every time that you spin the reels, a unique combination is formed each time.

Watch Video about How Slots Work

To verify the integrity of the RNG systems, software providers and online casinos alike have to pass government inspections and audits. Slots are the ultimate game of chance, as everything is random and there is nothing you can do circumvent that. This, in turn, means that anything can happen in the short team, with winning and losing streak being among the few possibilities.


Slots SymbolsNaturally, we cannot ignore the symbols in a slot game; they are one of the most attractive aspects of the genre. The symbols that adorn the reels are what we watch out for when spinning the same reels. They make the difference between winning or losing, with certain combinations of symbols being more rewarding than others.

Symbols in slot games are generally separated into two categories – basic and special. The basic type are simple to understand and they carry no interesting features. You simply have to line up several of them to win a smaller prize. They come in different tiers, with some symbols being more rewarding than others, though the lower the symbol pays, the more often it will appear on the reels. Essentially, there is nothing too interesting about the basic symbols, except when they line up just like you want them to.

The special category of symbols, on the other hand, is there to spice up the general gameplay and introduce new features in the game that basic symbols would otherwise be unable to. There are generally three symbols in this category – Wild, Scatter and Bonus. The Wild symbol has the ability to stand in for any basic symbol when needed, allowing you to complete winning combinations.


Slots PaylinesEarlier, we mentioned paylines and it is time to give you some idea what we mean by that. Payline refers to the combination of symbols that you can form when playing slots. In the early slot machines, a payline was formed as a straight horizontal line in the middle of the reels. In present day, paylines can be just about any form that you want, with various zigzag lines covering your reels. Granted, the addition of more reel also allowed for more paylines to be added, though the exact number of them is entirely dependant on the game in question.

Classic slots typically come with 1 to 3 paylines, whereas modern video slots feature anywhere between 25 to 50, on average. For each payline that you activate, you also have to increase the size of your bet by a certain threshold. While this increases your chances of forming winning combinations, it also increases the risk of playing as you are wagering more money.

The direction in which the symbols line up is also important. The vast majority of slots only reward you if your combination starts on the leftmost reel and continues along the adjacent ones on an active payline. Certain games do away with this rule, but those are few and far between. The Scatter symbols are traditionally not affected by the direction in which they are formed, as long as they go along the payline.

X-Ways to Win

X-Ways to WinAn alternative to traditional paylines is the X-ways To Win system. Whereas paylines require you to spin symbols along a designated pattern, this system will reward you for hit the same symbol on adjacent reels regardless of its position. This system does appear to be friendlier on the surface and you will likely experience more wins with it. The trade-off is that you have less control over the game. Since there are no paylines to activate or disable, the game’s minimum bet will be somewhat higher than on a more traditional title. We are talking about pennies here, so keep that in mind.

Whether this system is better than old-fashioned paylines is up to debate, but it mostly boils down to personal preference. There is no clear-cut answer to this and you should give both a shot to see which suits you better.

Types of Slots

Types of SlotsAs is the case with most casino games, there are multiple different variations of the traditional slots formula. While there are certainly different types of slots that you can play, the number of different variations is not as large as in blackjack or roulette. Slots are certainly a diverse genre, though this diversity is established through a variety of theme and aesthetics rather than drastic changes in the gameplay. Despite that, it is still important to cover the different types of slots that you will encounter during your visit to an online casino.

Classic Slots

Classic SlotsClassic slots are sub-genre of slots which try to emulate the look and feel of old-school fruit machines. They feature 3 reels and usually come with up to 3 paylines, though this is not set in stone. The gameplay is rather simple, making them perfect for players new to the world of slots. As such, there is not much to classic titles and you spin the reels.

The symbols are usually in the style of the old machines, with cherries, sevens, jokers and diamonds adorning the reels. Some games do include Wild symbols in the mix, allowing you to easily form winning combinations. All in all, there is not much to say about these games since they rarely come with bonus rounds, free spins or other such features. They are rather basic and you can easily get the hang of them after a few minutes. Though, if you do not like the classic format, odds are that you will become bored with them pretty quickly.

Video Slots

Progressive SlotsThe video slots sub-genre is the most common type of slots that you will find in the modern-day gambling industry. These are much more complex than the classic slots of days gone by and offer a more exciting and unpredictable casino experience. Whereas classic slots offer mostly the base gameplay loop, video slots have a tendency to pack more features altogether. You will likely find free spins rounds, bonus mini-games, more symbols – both basic and special – and much more paylines in the average video slot title as opposed to any classic game.

Moreover, video slots also go much deeper into specific themes and aesthetics than classic ones do. Whereas traditional titles mostly feature a single picture and a few basic symbols in the same vein to form a theme, video slots go out of their way to make the aesthetic be felt. This includes more emphasis on the symbol art, the background music, the bonus features and more.

As for the gameplay itself, video slots feature many paylines and reels than classic slots. The average video slot has between 25 and 40 paylines, though that number can up to 50 or 60 easily. What this means is that you can form winning combinations in ways that you would not even expect, though at the cost of higher bets.

Progressive Slots

Video SlotsThe progressive slots category is one of the most popular in the online gambling industry and the titles that make it up often receive a lot of attention. This is due to the jackpot attached to the particular game. Unlike standard jackpots, the progressive type only increases in value until it is won by a lucky player, after which, it resets to a set minimum value. Furthermore, the progressive jackpot is offered by the software provider, rather than the casino and this has some significant implications.

For one, the jackpot is pooled from all casinos that feature the game, instead of each website having its own unique pool. A small percentage of each bet made on the game across all online casinos that offer it is added to the jackpot. As you can imagine, this can cause the jackpot to rise to incredible values, especially on more popular titles. Seven-figure sums are not uncommon and some go even higher. At the moment of writing, Microgaming’s Mega Moolah title has just amassed over $18 million and currently rising.

House Edge and RTP

Return to playerAnother important factor in playing slots – and any other casino game for that matter – is the house edge and the return-to-player percentage. These are vital for you to understand how fair a game really is and whether is it worth playing in the long run. When we say house edge, we refer to the statistical advantage that the casino has over its players. It is what makes a gambling operation worth it and it is the primary way to generate revenue. The house edge is the total amount of money that the casino gets to keep as profits in the long run.

In most games, it is a few percent of the total turnover. For example, in a game with a house edge of 5%, the casino will pay out 95% of all money that enters the slot as winnings. This hypothetical 95% is the return-to-player percentage. The other 5% will be kept as profit for the house, hence the term house edge. The house edge is realized as the statistical difference between the payout ratios for a winning outcome and the probability of you receiving that outcome. Imagine the following situation, an outcome has odds of 1 in 100 to happen, while the payout for you getting that outcome is 95:1. That difference constitutes the house edge and it is the metric by which we judge the fairness of a given game. Granted, no game with a house edge is ‘fair’, strictly speaking, but the closer we get to equilibrium, the more worthwhile it is for players and the higher the house edge, the more we should avoid it.

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Find the answers of questions people asked so far:

Dan Georgina

How to determine which slot paying mechanic is the best?

Asked by: Georgina | Asked on: 2023-05-26
Answered by: Dan | Answered on: 2023-05-26

Choosing the right slot to play is often based on various factors rather than simply on the paying mechanic of the game. When you wish to choose which slot may potentially bring you the best return in the long run, you might want to consider the game’s RTP and volatility level. When you combine these two elements, you are able to get a somewhat accurate assumption of what you can expect from the slot in a longer gaming session.

That is why we suggest comparing slots not simply by their paying mechanics but also consider their RTP and volatility. That being said, if you prefer simpler gameplay with paylines or you enjoy ways-to-win or cluster-pay mechanics, you should consider which slots offering your favorite paying mechanic have the best combination of RTP and volatility.

Dan Thomas

Are slot results generated through RNG really random?

Asked by: Thomas | Asked on: 2023-06-05
Answered by: Dan | Answered on: 2023-06-05

Yes. The Random Number Generators (RNG) used by online casinos ensure that each result in a slot or any other casino game is random and cannot be predicted. That way, all slot players are guaranteed a fair gaming experience, letting luck decide the outcome of each spin. By using natural entropy, the RNG ensures that each spin on the slot provides players with a real probability of five identical high-paying symbols aligning in a winning line or triggering the jackpot prize. Just as in real life, the results in the slots you play at online casinos cannot be predicted by anyone and you will simply rely on your luck to end up a winner.

Dan Melanie

Where can I see the RTP of a slot game I am about to play at an online casino?

Asked by: Melanie | Asked on: 2023-09-11
Answered by: Dan | Answered on: 2023-09-12

You can easily find the RTP of any slot that you wish to play for real money by checking different reviews of the game available online. There is also the opportunity to check the official page of the provider who has created any particular slot to see if there is any public information about the game’s RTP. Many online casinos will also provide such information on their official websites, with casinos’ slot libraries often listing the RTP of each game they offer.

One thing to keep in mind when checking reviews to discover a slot’s RTP is that some providers allow operators to adjust the RTP rates of the slots they will offer to their patrons. That is why you may discover that the same slot may offer a different RTP across different online casinos. This is why it is best to try and find each slot’s potential long-term return on the official website of the casino.