How Do Online Slots Work

How Do Online Slots Work

Modern online slot machines have simple principles of operation and do not require you to dive deep and study many rules, so this gambling type is one of the most popular. Moreover, the slots category is the most extensive in most online casinos. Hundreds of providers create many slot machines, their portfolios consist of thousands of titles, and each game has unique features that distinguish it from all the others. Let’s discuss how do online slots work, what guarantees their fairness and how to increase the chances of staying in the black.

Random Number Generator Explained

A random number generator provides the principle of randomness, which creates excitement and makes the game unpredictable. This mathematical algorithm is the basis of any licensed slot machine; it determines which symbols, in what quantity, and in what places will appear on the reels after rotation. Moreover, previous spins do not affect future spins; for example, if you have made 20 unsuccessful bets in a row, it does not increase your chances of getting a payout on the next spin.

How Does RNG Work

A random number generator determines the spin results and does it in a split second, so there is no way to predict the outcome or influence it somehow. As soon as you press the button to spin the reels, RNG takes a random initial number and performs thousands of complex mathematical calculations.

Random factors influence the result, and you cannot predict it; this ensures absolute randomness and game unpredictability.

While working, a random number generator focuses on the parameters set by a slot provider. In particular, that’s about a return-to-player percentage and the level of risk.

What Are RTP, Volatility & House Edge

When creating slot machines, providers develop the design, interface, sound effects, and various mechanics, but this is not all. They also set specific operating parameters, the most important of which are:

  • RTP. This is a theoretical return-to-player percentage, which shows what share of money from the total investment the slot will give to all players. This parameter uses a very long distance of millions of spins to reach a given value; for example, if players invest $100,000 and the RTP is 96%, the total payout they will receive is $96,000. Remember that the slot pays this money randomly, so every player has a chance to stay in the black. The remaining $4,000 is the profit the casino and the slot provider receive.
  • Volatility. All slots have a specific level of risk, which determines the frequency of payouts and their size. The higher the volatility, the more unpredictable the results; long losing streaks are possible, and the potential payout may be less than your initial bet, as well as exceed it tens of thousands of times. Low-volatile slot machines provide prizes very often, but their size is usually small.
  • House Edge. This parameter is valid only in table games and provides a mathematical advantage for the casino, which allows it to get stable profit in the long run. For example, the house edge in European roulette is 2.7%; the Zero sector provides it.

You can check these and other parameters in the slot’s Help section or on the provider’s website.

Guide on How Do Online Casino Slot Machines Work

Now let’s discuss in more detail how do online casino slot machines work and what features of their gameplay exist. This information can come in handy during your gaming sessions and when choosing a slot.

What Are Slot Machines

In simple words, slots are a kind of gambling game that features reels with symbols. You make a bet and press the Start button to spin the reels; after its completion, the results are instantly summed up, and you either lose or get a payout.

Slot machines at online casinos
Reels are a must for any slot machine

Table games are part of the slots section at many casinos; in fact, these are different gambling types. However, table games can also use a random number generator to work.

Basic Rules

As it was said earlier, all slot machines feature different reel types, which is a must; their number may vary from one to more than a dozen, but each has different symbols. The primary condition you have to meet to get a payout is the formation of a combination of identical images. However, many modern slots use additional mechanics that considerably change the gameplay:

  • Megaways. Each spin brings a different number of symbols, which changes the number of paylines.
  • Gigablox. Large symbols that occupy space on multiple reels at the same time can come up.
  • Cascade Spins. Symbols that bring a payout disappear from the playing field, and new ones appear in their place.
  • Clusters. It is not necessary to form a line to get a payout in such slots: you just need to collect the required number of identical symbols next to each other or regardless of their location.

The amount of prize money you can count on depends on the number of lines, symbols that form a combination, and their face value; rarer images are valued higher.

Bonus Rounds & Wager

All online slots work using a large number of mechanics that are responsible for more diverse gameplay. One of them is a bonus round: this is a special game with a higher payout potential.

Providers usually use two ways to implement this round. The first is a series of free spins with additional mechanics: sticky wilds, cumulative multipliers, special symbols, and so on. The second way is a bonus game, which usually takes place in the other location; it may offer to choose items, spin the Wheel of Fortune, open special chests, etc.

Unlike funds received by participating in casino promotions, the money received during a bonus round does not require wagering. After receiving it, you can immediately spend the sum or withdraw it through the cashier.


One of the few parameters you can affect when playing slot machines is the bet size. You can change it using the control panel in the slot’s footer. In some slots, you have to choose an amount from the list, while in others, you can change the number of lines and coins, as well as the coin value.

The bet size must comply with the minimum and maximum limits set by the provider; such restrictions exist in all slot games.

Spin cost does not affect results, so increasing or decreasing a value does not change your chances of winning.

Slot Machine Symbols

Each slot machine has a unique set of symbols that come up on the reels; there can be 5, 7, 10, or even more of them. The primary condition for getting a prize is to collect combinations or a certain number of identical symbols on the reels, and the rarer they are, the bigger your payout.

Symbols in slot machines
You can find a list of all symbols and their value in the slot rules

The most common symbols are card values, but they are usually the lowest paying ones. The appearance of more valuable symbols depends on the game theme: these can be fruits, animals, insects, movie or comic heroes, musicians, mystical creatures, you name it.

Slot Lines

Payline is a sequence formed by identical symbols after a spin. Slot machines with these mechanics use a different number of lines; for example, classic games feature from 1 to 20 paylines, and Megaways slots offer hundreds of thousands of them.

The more active lines there are in the slot, the higher your chances of forming one of them. However, remember that increasing their number means that volatility also grows, and the average payout size, especially for low-paying symbols, decreases.

Wild, Scatter & Multiplier Symbols

In addition to standard symbols, modern slot machines offer several special ones that diversify gameplay greatly. Scatter is one of the greatest examples: this symbol usually activates free spins or triggers a bonus round. You need to collect two to five of these images to unlock the feature.

A multiplier is a symbol that increases the total payout per spin several times; several multipliers can be summed or multiplied by each other.

Wild is a universal symbol that replaces any other image to form a payline; there are different kinds.

Wild TypeFeatures
StandardA simple wild with no additional features
StickyIt gets fixed on the reel for one or several spins
ExpandingA wild increases in size and takes more than one cell
MovingIt can move on the reels

Scatters, multipliers, and wilds can collaborate in many ways; sometimes, one bonus symbol is responsible for several features at once.

Jackpot Odds

Although the chances of winning the jackpot are minimal, and the larger the prize pool, the lower they are, having such an opportunity creates additional excitement. That is why many games offer to fight for fixed or cumulative jackpots. The first has a specific size, which depends on your bet size, and the second constantly grows thanks to all players’ bets.

Free & Real Money Games

Most online slots work in the USA in standard and demo modes. In the first case, you play with real money and risk it, but you can get real payouts, while in the second case, you use virtual chips instead of cash, so there is no risk, but it is also impossible to win.

Free slots
In some casinos, you can choose between two modes of play

You should choose which mode suits you best, depending on your goals and willingness to take risks.

Best Software Providers

Among hundreds of providers who create slots, several dozen of the most popular studios exist. They offer modern games that become extremely popular and introduce progressive mechanics and exciting features. Large studios can also afford to invest more money in game development, so their slots have top-notch graphics and high-quality animations and are perfectly optimized for handheld devices.

The list of most popular providers includes Pragmatic Play, Endorphina, Yggdrasil, Nolimit City, Microgaming, Thunderkick, Big Time Gaming, and many other studios. Be sure to check whether these providers are available in the game catalog of a particular online casino before signing up and making a deposit.

Slot Machine Fairness & Audits

The safety and fairness of online slots work are ensured in several ways: the first is a reliable random number generator, which third parties cannot influence.

Independent auditing companies check RNG work; as a result, if it is fair, they issue appropriate certificates; the most famous gambling auditors are eCOGRA and iTech Labs.

Hashing protocols also provide safety; the results of each spin are recorded by a special code, and you can compare the actual outcome with RNG results.

How to Play Online Slot Machines

Thanks to the active popularization of online casinos and their legalization in the US and dozens of other countries, gambling has become available to many customers all over the world. Once you understand the basic principles of online slot machines, you can start playing, so select an online casino, sign up, and activate your no deposit or welcome bonus if possible. Once the money is credited, you can choose a game and start making bets: just decide on a bet size and spin value and press the Start button to launch the reels.

Bonus bet in slots
In some slots, you can raise your bet to increase the probability of activating the bonus feature

If the game session turns out to be successful, you can withdraw the money through the cashier, but before this, you usually have to complete verification.

Tips on How to Win Slots

You will never know a spin result until you make it, and no strategy can guarantee you a win. That’s why the recommendations rather aim to minimize your risks:

  • Choose slot machines with high RTP.
  • Divide your money into several bets (at least 70).
  • The smaller your bankroll is, the lower the volatility of the selected slot should be.
  • If you face a long losing streak while playing a particular game, it is better to change it.
  • After receiving a large payout, we also recommend changing a slot machine.

If there is such an opportunity, test the game in demo mode before risking your money, so you can understand the mechanics and whether you like the slot machine or not.

How Does Psychology Work in Online Slots

When playing slots, it is crucial to understand how human psychology works regarding gambling in order not to get addicted. Every time you receive a large payout, your body produces the joy hormone. And the longer you play, the stronger the feeling of happiness you associate with gambling. This correlation becomes especially strong after a huge win; as a result, there is a desire to get back and win more. However, the problem is that another big win may never happen.

Losing streaks can last many days, weeks, and even months, so you should not risk money, the loss of which will create problems for you and your family’s daily life.

Remember the principles of responsible gambling, and do not let your emotions rule you. Determine your bankroll in advance, do not borrow money, do not risk funds you are not prepared to lose, and stop playing if you feel intensely hostile and angry.

How Do Casinos Make Money on Slots

Online slot machines work to provide casinos with stable profit with the help of RTP, so remember that casinos always win regardless of your or other players’ results.

This information is public, and no one is hiding it. You can find the RTP of most slot machines on their providers’ websites to understand how profitable it is in the long run.

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No. Online slot machines work for US players just like in any other country.

Yes. All slots are adapted to play on smartphones, and their interface automatically adjusts to any screen size.

No. Usually, two or three symbols are enough, depending on their value, but keep in mind that the longer the line, the bigger the prizes.

You can return to it at any time or instantly know the result after restarting the slot machine.

No. All games are hosted on providers' servers and are only available online. It is not possible to download them to your PC or smartphone.

Publication Author
Donald Peterson
Author of articles
Donald Peterson is an avid gambler from Edmonton, Alberta, who also writes about his experience with casinos. He’s been in the business for over 10 years, following the ever-changing industry landscape. His articles are aimed at helping beginners with choosing casinos, suitable games, and strategies.
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