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Complete Guide to Online and Land-Based Slots

Slot machines are by far the most popular games both at online casinos and at land casinos. The games are easy to play, can provide hours of entertainment, and also offer the chance of enormous winnings. In this guide, we will teach you all you need to know about slot machines so that you can have as much fun as possible when playing.

History of Slot Machines

Slot machines have a history going back more than a century. The first machines appeared towards the end of the 19th century and it isn’t entirely clear which was the first. One of the very earliest machines was created by the New York company Sittman and Pitt in 1891. The slot had 5 drums and 50 playing cards and players would win a payout if a poker hand landed on the reels. It was hugely popular in bars and cost a nickel to play. In order to increase the house edge two cards were removed, the 10 spades and the jack of hearts. However, the machine didn’t pay out money and players would receive their winnings in the form of free drinks and cigars at the bar.

One of the earliest machines that is recognisable as a slot is the Liberty Bell, which was created by Charles Augustus Fey around 1895. The game featured three spinning reels, a handle on the side, and a slot in which to insert money. Furthermore, he did not use cards; rather he used five different symbols, hearts, diamonds, spades, horseshoes and a liberty bell. Its top payout was awarded for landing three bell symbols, and that is where the machine got its name.

One of the most successful developers of early slot machines was Herbert Mills. His game, the Operator Bell, was found in many shops and tobacconists across the United States. He also introduced fruit symbols, such as lemons and cherries, and the machines would payout chewing gum and sweets of a matching flavour. It was also the first machine to use the BAR symbol, which was based upon the logo of the Bell-Fruit company. The games were so successful that until this day many people refer to slots as “fruit machines”.

Slot machines did not change in any fundamental way for a very long time. Players pulled a lever to start the reels and won payouts for landing matching symbols. It was Bally Technology that released the first fully electric machine in 1964, Money Honey. However, despite having electronic reels, the game still made use of a lever to ensure that players would recognise what it was, and the machine could make automatic payouts of up to 500 coins.

Fortune Coin developed the first proper video slot in 1976. The machine made use of a modified 19-inch Sony television for its display and the game was first rolled out at the Las Vegas Hilton Hotel. The Nevada State Gaming Commission soon approved the game and it was not long before it was a popular game along the Las Vegas Strip.

With time, the technology behind video slots continued to progress. The development of the virtual reel in 1984 by Inge Telnaes was a major milestone. He developed the way of mapping symbols and spaces from a physical reel onto a virtual reel. This increased the number of possible combinations of symbols and spaces, which allowed game designers to offer bigger jackpots.

Another big milestone was the release of the game Reel ‘Em by WMS Industries Inc. in 1996. It was the first slot to have a second screen bonus game, which was an instant hit with players. Since then, slots and bonus features have only become more advanced. With the advent of online slots, developers have more freedom than ever before to produce games that will appeal to a wide range of players. With online casinos unrestricted by physical space, slot players now have more choice than ever before.

Playing Land-Casino Slot Machines

When you visit a casino, you will find many different types of slot machines on the casino floor, and it is important that you understand the difference between them. Here is a brief guide to the most common of them.


This form of slot machine was first a hit in Australia but over the last few decades, it has become extremely popular in casinos around the world. It allows players to choose how many paylines they want active and how many coins they wish to bet per payline. In general, it is advised to bet at least one coin per payline, so that they are all active, and players should also check the paytable to ensure that there are no betting conditions for activating bonus features.


These games were the predecessors to those described above. They give players the ability to choose how many paylines they want active, but the betting is limited to one coin per payline, as a result of which they have declined in popularity.


In this type of game, each extra coin that is bet unlocks more winning combinations. The number of available winning combinations has a big impact on the hit frequency of a slot. As a result, it is always recommended to bet the maximum number of coins on these machines.

Hidden Buy-A-Pays

This refers to any slot machine where the bonus features are only accessible when betting the maximum number of coins. By doing so, the machine’s payback percentage will receive a big boost and make them far more profitable. Because of this, it is always necessary to check a game’s paytable before playing to look for any bonuses that require maximum coins to activate.

Straight Multipliers

This type of slot machine gives players the ability to activate all winning combinations by betting a single coin and any extra coins bet will increase the payout multiplier. It means that betting three coins offers three times the winnings of a single coin.

Bonus Multipliers

These slot machines also have all combinations active with a single coin and additional coins will multiply any winnings. However, these slot machines offer a bonus payout that can only be won by betting the maximum number of coins.


When playing a progressive slot, a portion of every bet is contributed to the jackpot pool. The jackpot continues to grow until it is won and it then resets to the base amount. It is nearly always necessary to bet the maximum number of coins to be eligible for the progressive jackpot.

Combination Slots

These are simply slots that combine two or more of the machines described above. You may find a multiplier with a buy-a-pay, or a multi-line progressive with a hidden buy-a-pay.

A Note on Land Casino Slot Etiquette

If the casino you are visiting is largely empty, then there is no reason why you can’t play on multiple machines simultaneously. However, if the casino is busy it is important that you limit yourself to just one machine, and the casino may even have a policy dictating this.

Similarly, slot machines normally come with one seat attached and if you take that seat without playing, then you are preventing others from playing the game. Not only may this annoy other players, but also it is likely to anger the casino, as you will be preventing it from making money. In other words, don’t use gaming seats unless you are intent on playing.

If you need a break while playing a slot machine but want to return to it soon after, then there are a number of ways of signalling your intent. A common way used to be leaving a coin cup on top of the machine. However, today not many casinos use coin cups. As such, players will often tilt the chair so that the back rests against the machine. As long as you are not gone for too long, then this should be fine.

Essentially, if you remain friendly and considerate of the needs of both the casino and the other players, then you should be able to have fun at the slot machines for hours on end.

Understanding Online Slots

There is not a huge difference between land-based slots and online slots, but the games are not quite the same. Both types of games use random number generators to determine the results, both types of games use reels and paylines, and both offer a variety of bonus features. However, you will notice a number of differences. Online you will find fewer progressive jackpot games and fewer games with bonus wheels, while online slots often offer more wagering options.

At some land casinos, progressive slots can occupy a third of the casino floor, or even more. This is particularly true of games that offer multilevel jackpots, as their bright displays and sound effects attract players from across the casino. While there are plenty of progressive jackpot slots online, they are not used to attract players in the same was as at land casinos.

The same is true of bonus wheels. In land casinos, these are big bright attractions that can be seen from a great distance. Online they are not going to draw in players in the same way, and that is why developers tend to stick to bonus features such as free spins and picking games.

A major advantage of online slots is the flexibility in betting. Land casino slot machines are often linked to a specific coin denomination, for example, you will find $0.01 machines that allow bets of 1 cent per payline, $0.25 machines, $1 machines, and so on. Even on games that offer multiple denominations, the options are normally limited. Online slots are far more flexible and players will most likely be able to play any game in denominations that fit their budget.

Randomness in Online Slots

A major concern of slot players is that the games they are playing are truly random and fair. Players are aware that the games are programmed and that there is a fixed RTP, which often leads to questions about how the games can be fair.

However, the games use Random Number Generators (RNG). They use advanced algorithms to calculate their numbers, which ensure that the results are truly fair. In order to understand the programmed aspect, it is possible to make an analogy with Roulette. An American Roulette wheel has 38 numbers, which means that the odds of any specific number coming up are 37:1. However, casinos pay 35:1 for a winning straight up bet. The difference between these two figures is kept by the casino, which translates to a 5.26% house edge. In that way, Roulette can be said to be programmed in the same way as a slot machine. The results are random, but the casino knows that over time it will have a consistent house edge.

In licensed jurisdictions, developers of online slots must submit their RNG for vigorous testing to ensure that it is truly random and fair. There are a number of independent testing laboratories that undertake this work, and very often, you will be able to find the certificates of randomness on the casino website or the developer website.

RTPs, Volatility and Hit Frequency

You will often hear people talking about games’ RTPs, volatility and the hit frequency. These concepts are all important to understand and will help you choose which games to play.

The RTP, or Return to Player, (also known as the payback percentage), is the proportion of bets that are returned to players as winnings. For example, if a slot has an RTP of 90% then ultimately it will payout $90 for every $100 bet on it. However, this is calculated over a vast number of spins, and it is impossible to predict whether a player will win 5%, 10%, 70%, 110% of their money, or any other amount.

The hit frequency refers to how often a machine will award a payout. For example, if a machine has a hit frequency of 8% it means that 8% of spins will result in a winning combination. It may be tempting to look for machines that have very high hit frequencies, but it is important to remember that a “win” may only cover the bet per spin or be even less.

This is where the concept of volatility or variance comes in. A low volatility slot will have a high hit frequency of small wins, in other words, you can expect to win small payouts very regularly. A high volatility slot will have a low hit frequency of larger wins, i.e. it will award larger payouts but not very often. It is important to be aware of this when playing as on a high volatility game, you may have to go through many spins before winning anything, and this may eat through your bankroll.

Slot Machine Bonus Features

Whether you are playing online or offline, slot machines offer a huge number of different bonus features. Here is a guide to the most common of them.

Wheel Spinning Bonuses

Originally, these bonuses involved a mechanical wheel that was fixed on top of the machine. Today, the wheel may be virtual, but it works in the same way. When you trigger the bonus round you then get to spin the wheel and it can award a cash payout. Bonus wheels do not only award cash prizes, they may also award free spins, multipliers, jackpots, or trigger additional bonus events.

Pick’em Bonuses

This is a very common form of bonus game both online and offline. Essentially players are asked to choose from objects on the screen to reveal prizes. The objects will normally relate to the slot’s theme, for example in a nature themed slot the objects could be different animals or plants. Sometimes the games can be multilevel with players advancing towards bigger prizes until they uncover ‘collect’. Players may also reveal other prizes such as additional picks or special multipliers.

Free Spin Bonuses

Free spins have become the most common form of bonus feature. Essentially players are awarded a certain amount of spins that they do not have to pay for but that can award real money winnings. Very often, the free spins will come with additional bonuses such as payout multipliers, expanding symbols, extra wild symbols, and so on. Furthermore, it is often possible to retrigger the free spins and that way win a huge number of them.

Mystery and Skill Based Bonuses

A mystery bonus is one that is awarded at random. In other words, it is not triggered by landing certain symbols and there is no way of knowing when it may begin. For example, a mystery bonus may add extra wild symbols to the reels, shuffle the existing symbols around to form a more valuable win, or award a payout multiplier. In some games, there are also mystery bonuses that trigger progressive jackpot games (although often the game will state that the larger the bet, the better the chance of triggering the feature).

Skill based bonuses are rarer, but they are growing in popularity. They are simply bonus features that require some form of skill, such as shooting at a moving target.

Community Style Bonuses

These are features found almost solely in land casinos. They aim to create a social atmosphere around the slot machines with multiple players involved in the bonus event. The bonuses take many different forms, but ultimately, they give slot machine players a chance to chat with those around them and possibly win a bit more.

Slot Machines Are Ultimately Simple

There is a great deal of superstition surrounding slot machines, particularly at land casinos where players talk about hot and cold machines. However, ultimately, they are purely games of luck and there is nothing that you can do to influence the outcome of a spin. As such, they are very simple games and do not require any advanced thinking or strategizing.

That said, it is important that you understand what type of game you are playing and exactly what it has to offer. Having read this guide, you should now be equipped to understand any slot machine you come across, either online or offline, and can start enjoying the excitement of every spin of the reels.

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