How Do Slot Machines Work?

by Tim | Mar 24, 2023

How Do Slot Machines Work?

Online slots in the UK are undoubtedly the most popular form of casino game. However, slots weren’t always the belle of the ball and were originally put into brick-and-mortar casinos to entertain the more casual casino-goes.

Unlike casino table games, slot games don’t require any gambling knowledge and are based on luck, which means that anyone can hit the big jackpot. Slot machines soon became the most popular and profitable game in town, and so they made their way from sidepiece to centre stage in most casinos.

You’d be hard-pressed to find an old-school lever-type slot machine these days, but the concept in online and computerised slot machines is still the same. So, if you’re wondering, “How do slots work?” in their modern form, you’ve come to the right place! 

Let’s take a look at what you need to know about slots today.

What to expect with modern slot machines

There are two main types of slot machines that you will find today, and both use the amazing modern technology that we now have on offer.

The first of these is the computerised slot machine. This is the machine that you’ll still find in the hundreds on the casino floor or in pubs and other establishments. They look very similar to old-school slot machines, and you can even still pull the lever to spin the reels, but they are computer controlled rather than mechanical.

The second type of modern-day slot machine you’ll come across are those that you’ll find in online casinos. These are the machines that have truly tapped into technology and offer a huge range of options and possibilities that in-person machines never could. Who knows where the future of slot machines will go?

So, let’s take a look at the way that these two different machines work and the biggest differences between them.

How modern slot machines work

Three red number 7 symbols in a row on a slot machine.

So, how are slot machines programmed? Although computerised and online slot machines look very different, the technology that they use to determine who wins and who doesn’t win is very similar.

Slot machines will have three reels at a minimum, but many modern slot machines will have more. Reels are the vertical lines that spin the symbols when you play slots, while paytables are the horizontal lines across the reels that show the combination of symbols as they land. Old-school physical slot machines had around 20 symbols per reel, but digital technology means that slots today can have as many as 256 virtual symbols with millions of different possible outcomes. 

You may be wondering how the computer determines when the reels will stop spinning and which symbol combination is going to land on the screen. A random number generator is responsible for all of this. It generates thousands of numbers per second, each of which fits into a different combination of symbols. The instant you spin the reel or press the spin button, the random number generator determines whether you win or lose. If you match the identified payline, then you win. 

Contrary to popular belief, slots are certainly not rigged, and these random number generators ensure that each spin is unique and unrelated to any previous future or past spins. This also puts the myth that machines run hot or cold to rest.

Payouts, RTP, and odds of winning

When it comes to payouts, the return to player (RTP) percentage and odds of winning in online slots will vary from game to game and machine to machine. One of the best tips for playing slots is to check out the following information before you give it a whirl.


You should have a look at the paytable of any slot game before deciding to play. They give players vital information about the game, such as the different winning combinations and how the symbols in these combinations should appear in the paylines. The paytable will also give you the value of the symbols. It should also provide you with information about payout when it comes to landing the same symbols across an active payline.


The RTP percentage is one of the most important aspects of online slot games. It is the most likely indicator of the odds that you will get when playing slots. Slot games are pre-programmed to return a specific sum throughout a number of cycles or spins.

For example, if a slot has an RTP of 96,10%, this means that for every £100 wagered, a player should expect a theoretical return of £96.10. However, you must keep the word “theoretical” in mind. This doesn’t mean that every player will get back this £96,10% of the money they spend on the game themselves, but that the machine will pay this back over a certain time span. One big jackpot every few months could mean that no one else makes money back for a period of time.


Of course, then there’s the volatility of a slot machine, and this indicates whether you’ll win smaller prizes more often or bigger prizes less frequently.

A slot machine that has high volatility is less likely to pay players back small sums over a period of play, but if they do win something, it’s likely to be a bigger, more substantial sum.

On the other hand, lower volatility slots will pay out smaller sums to players more frequently. 

Learn more about slots at The Phone Casino

Of course, the best way to learn about something is to experience it firsthand, and that’s why it’s always a good idea to try out a free version of a slot machine before playing. At The Phone Casino, we have hundreds of different online slots for you to choose from. Our free demos allow you to try them out first to find the perfect fit. Register with The Phone Casino to get spinning.

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