Online Slots Guide

Online Slots Guide

Read TheCasinoDB Ultimate Guide to Online Slots and learn about the history of slot machines as well as tips on how to get started playing slots plus find the latest slot games to be released at a casino near you.

Guide 5th July 2019


slot reels bar bar

As a kid, I could never get enough of Southend. Summer days out with Mum and Dad, and then as a teenager venturing there with a couple of friends on the bus, and even on one occasion doing the 20 odd miles each way journey from central Essex on our bikes. On the one hand, it seems a lifetime ago, yet at the same time I can still smell the smells and hear the sounds as if I was there yesterday.

If you think I am talking about the sea air and the sound of waves crashing onto the muddy beach, I’m sorry to have to disappoint you. I’ve never been much of a one for getting sand between my toes. No, I’m talking about Mr B’s, The Happidrome and the Granddaddy of them all, The Kursaal.

Looking back on it, I’m not sure how my parents summoned the patience to drive all the way out there – it took plenty of time in a Vauxhall Victor, believe me – drive up and down Western Esplanade for half an hour searching for a space and then traipse around in my wake for hours on end and I rushed from one amusement arcade to the next. They were probably as excited as I was when I was old enough to take that first bus journey on my own!

Yet for me, there was something magical about stepping through those doors, from the bright light of a summer’s day into momentary darkness as my eyes adjusted to the dim light and my other senses were assailed by the smell of stale cigarette smoke and junk food accompanied by a cacophony of sound from the fruit machines, driving games and even, in one of them, a seemingly never-ending game of bingo at the back of the arcade.

slots arcades

And so it is that I can trace my love of slot machines back to these childhood memories. Of course, back then, they were called fruit machines, or among the sophisticated, one-armed bandits. These days, a 14-year-old would never be able to waltz in and start playing the slots, and the thought of him doing so with a Player’s No. 6 hanging out of his mouth would be cause enough to summon the police, the child protection services and probably the coastguard for good measure.

But these were different times. If you had some coins in your pocket, you were welcome to go in and feed them to the machines.

As the years rolled by, I got to know each and every machine in my local pubs. Not that I was a big drinker – well no more than the average 18-21-year-old – and I would get that same tingle of excitement from the news that a new machine was coming as I used to feel walking into the Happidrome after an absence of months. 

Fast forward to the present day, and the world of slots is bizarrely different. On the one hand, machines are cordoned off in adult only areas in high street arcades and sterile motorway service areas, monitored by CCTV and watchful attendants in case an under-18 tries to get close. No more games on the fruity while we wait for our fish and chips today! 

Yet on the other hand, the advent of online gaming has made the possibility of winning money on slot machines, and winning big, at that, easier and more accessible than it has ever been in history. 

One thing, however, hasn’t changed, and that is the fact that slot machines do not come with an instruction leaflet. I learned my way around them through a combination of observation and trial and error. 

One thing that I soon found out, however, was that once you have mastered the underlying principles, you can soon pick up the finer details of the different machines. It’s probably a little like cake making, in that once you know how to make the perfect sponge, you can easily add different varieties of icing. 

But how to learn those basics? Given that you are here, the chances are you are a little long in the tooth to cycle down to Southend and hang around the Kursaal looking over people’s shoulders, and from what little I heard about the place around the turn of the millennium, that would probably be a bad idea for all sorts of reasons these days. 

So to save you that embarrassment, come with me and I will show you everything you need to know to achieve the slot machine equivalent of the perfect sponge cake. Have you got plenty of 10p pieces? Then let’s begin.

A Short History of Slot Machines

Chapter One

Most people credit the manufacture of the world’s first slot machine to a New York company by the name of Sittman and Pitt. The game contained five drums, containing a total of 50 playing cards. The machines became extremely popular throughout bars in New York, and soon became a common sight.

Players would insert a coin, pull a lever and it would literally deal them a poker hand. There were no cash payouts, but a good hand would be worth some sort of prize – perhaps a free drink or a cigar.

You will notice that there were 50 cards, not 52. What do you think were left out, a couple of 2s, perhaps? No chance, even then, the concept of the house edge was well understood, and the ten of spades and jack of hearts were omitted to halve the likelihood of a royal flush. 

liberty bell slot

The Liberty Bell

That first machine was tremendous fun – indeed it still is, if you’re willing to travel over to the States and pay out around $20,000 for one at an antiques auction – but the next innovation looked much closer to the modern day slot machine. Charles Augustus Fey’s Liberty Bell was simultaneously simpler and more complex than its predecessor.

It was simpler in that instead of the countless combinations presented by a deck of cards, it had just three reels, each of which contained five symbols – hearts, spades, diamonds, horseshoes and the eponymous Liberty Bell. A pull of the lever sent the reels in motion, and here is where the additional complexity came in – the machine would automatically pay out a cash prize for matching three symbols, with the jackpot payable for three Liberty Bells. 

Americans couldn’t get enough of Fey’s machine, and he should, by rights have become an overnight millionaire, but for two factors. The first was that he had neglected to patent his invention, so before you could say three liberty bells there were variations on his theme being manufactured left, right and centre. 

The second problem was America’s usual uncomfortable relationship with gambling. Not to put too fine a point on it, slot machines were banned in 1902. 

slot bars

Fruit machines raise the BAR

Ever wondered why the more logical symbols that are closer to the suits of playing cards suddenly transformed into lemons, plums and that strange BAR sign? It arose during the “slot machine prohibition” period of the early 20th century. You see, having a great idea and then giving up on it just because it becomes illegal is definitely not what the American Dream is all about. 

Specifically, it was the cash prizes that caused the problems with the law. Thus commenced the age of the fruit machine. Fruit symbols were wholesome and did not have the gambling connotations of hearts and spades, while prizes were in the form of sweets and chewing gum of a matching flavour. In 1907, Herbert Mills of Chicago unveiled the Operator Bell. Within 12 months, it was a common sight in shops, tobacconists and bowling alleys far and wide. As well as the fruit symbols, he added the company logo as a clever marketing ploy. That’s right, it was the BAR that we still see today. 

The electronic age and beyond 

It was not till the 1960s that there was any further substantial change in the nature of slot machines, and these came with the invention of the first fully electromechanical devices. Strangely, although the reels operated entirely electrically, the game was still activated by a pull on the lever, as it was felt the world was not quite ready to handle a simple press button instead. 

From there, the evolution follows a familiar path with which we are familiar. The first video slot arrived in the Las Vegas Hilton in 1976. It used a modified 19” Sony television and was hailed as a wonder of the modern age. Within a year, video slots could be seen everywhere you looked up and down the strip, although I can’t remember anything so exotic making it as far as Southend in the late 70s!

In the mid 1990s, WMS Industries brought out a machine called Reel ‘em. This marked just as important a watershed, as it was the first slot machine to feature a bonus game on a secondary screen. It seems strange to think that these sorts of games are such a relatively recent innovation. 

Of course, the mid 90s was also the period when the internet really took off, and it was not long before online casino games started to appear. Initially, these were mostly table games like roulette and blackjack, but before we knew it, slots joined the party. 

This more or less brings us to present day, so enough of the history lesson. You have come here to learn how to become an ace of the slots, so let’s dive on in. 

Playing Slots

Chapter Two

So you want to play slots? Well, you’re in good company. According to apocryphal history, they were originally introduced to the Vegas casinos to give the ladies something to do apart from powder their noses while the menfolk were at the important business of poker, blackjack and roulette.

Yet these days, slot machines take up more than 70 percent of the square feet in the Vegas casinos. There might be some truth in their origins, as it is also fair to say that they have a more universal appeal, not only among both sexes, but across all age groups and demographics.

They are also the first place that novices tend to head when entering the hallowed halls of a casino for the first time.

low stakes slot machines

Why play slots?

So why is it that slots are so popular? Is it because you stand a better chance of winning? We will talk about house edge statistics in a little while, but for the moment, suffice it to say that no, it’s not that. 

Perhaps it is because they seem so unthreatening. As someone who has worked in and around casinos for more than a quarter of a century, I know that first timers often feel nervous about approaching the gaming tables to play blackjack, roulette or craps.

By comparison, the slot machines are a familiar sight and are a solitary activity, so there is less chance of making some social blunder. They are also simple, at least in as much as the basic principle is concerned. You put in your coin, press the button and see whether or not you get a payline.

Slots also involve a far lower financial investment than other casino games. Obviously, it varies from one casino to the next, but typically, the minimum bet on a game of blackjack is going to be £5. Yet there are still slot machines where you can play for as little as 20p per spin, or even less.

A lower wager should mean your bankroll is going to last longer, but bear in mind that a spin on a slot machine is over much faster than a hand of blackjack. To add a little context, if you have a full table of players, each hand will take at least a minute, so that translates to perhaps 50 wagers per hour. I’ve seen people place ten times as many on a slot machine in the same period. 

gambling cash returns

Serious returns

Another big draw of the slots is the possibility of a huge return on investment. Play blackjack, and you are mostly dealing with even money odds, with 3/2 available on a natural. At roulette, you can place a straight up bet and get odds of 35/1, but that is the biggest payout available. And at poker, the prize pot depends on the players. 

Yet with a slot machine, the return can be truly awesome. The highest ever payout happened at the Excalibur Casino in (where else?) Las Vegas back in 2003. This was an eye-watering $39.7 million – and it came from a $3 bet. 

The odds of winning like this are astronomically remote – consider the thousands of people betting on thousands of machines in Vegas every single hour, and we have to go back almost 15 years for such an event. But, like the Euromillions and other Lotto type gambles, even if the odds are unfavourable and the house edge is obscene, the fact that the possibility exists is enough to keep people coming back for more over and over again.

Even if seven figure payouts have a probability with odds similar to those a bookmaker would give on Elvis being alive and well and driving a milkfloat on the moon, there is a good chance that regular slot players will get the odd payout in the hundreds. 

So given the relatively low wager, does that mean slots are a more shrewd gamble than other casino games? To answer that question, we will need to delve into some mathematics and take a look at payback percentages and the house edge. 

About the house edge

A casino needs to earn money. I’ve worked in casinos for many years, and much as I have always enjoyed my job, I have bills to pay like everyone else, so they have salaries and other overheads to pay out. Also, like any other business, they have shareholders who expect to see a profit at the end of the year. 

This is where the concept of the house edge comes in. On a roulette wheel, you will get an even money pay out on black or red. But the odds of a win are actually a little less than 50 percent, due to that green zero slot. The odds of the ball landing there are 37 to one, or 2.7 percent. That is known as the house edge, and it is how casinos make money. 

Some roulette wheels have two zeros, and you do not have to be Stephen Hawking to work out that this equates to a bigger house edge – in this case, it is 5.3 percent.

The house edge is the mathematical basis of the old saw “the house always wins,” and from your perspective as a gambler, you will want either a game with as low a house edge as possible, or a strategy to reduce the house edge as much as you can.

In the above example, the solution is clear – if you have the choice, you should always choose a single zero roulette wheel above a double zero one. In blackjack, the house edge is about 5 percent, but by following some basic strategy guidelines that are based on statistical probabilities, you can reduce that by 1 percent or even more. 

Payback percentages 

So what is the house edge on a slot machine? Here, it is more common to talk about the “payback percentage,” which is essentially the other side of the coin. Let me explain. The payback percentage is the proportion of the money going in that gets paid out. So a payback percentage of 95 percent means a house edge of 5 percent. 

You will probably not be surprised when I tell you that payback percentages vary between machines and locations. In years gone by, slot machines were like the wild west, and payback percentages as low as 70 percent were not uncommon. That is a massive 30 percent house edge! No wonder I used to always return penniless from Southend!

These days, the industry is rigorously regulated and controlled. Over in Vegas, the payback percentages vary depending on the type of slot machine – there, they still have 1-cent slots, and although the wager is miniscule, the payback is only around 82 percent. This rises to 89 percent for 5-cent games, 92 percent for 25-cent games and 94 percent for 1-dollar games. 

Here in the UK, the law states that payout percentages must be 80 percent or higher. The ones at the lower end of the scale are the fixed odds betting terminals that are commonly found in betting shops. Someone once described these things to me as “the crack cocaine of gambling,” and I find that hard to argue. I won’t be talking about them here, beyond advising you that if you are in a betting shop, you’re better off putting your money on a horse. Even a three-legged one. 

Typical slot machines in UK casinos pay out around the 92-93 percent mark, while you will generally find higher payout percentages on online machines – simply because an online casino has far lower overheads than a bricks and mortar one. 

Whichever way you look at it, the house edge is greater on a slot machine than it is on a table game. However, the lure of that outside chance at winning a life changing amount of money, along with the speed, simplicity and anonymity of slot machines still makes them by far the most popular feature in every casino. 

So now we have a better idea of why you might be attracted to the slot machines. It is always nice to know why we are doing something, and I wish someone had explained it to me all those years ago on Southend sea front! 

You also have a better idea of what you stand to win or lose on a slot machine. So now, let’s see how the mechanics of even the most rudimentary slot machine can combine with the mathematics to blend “programming” with random results.

How Slot Machines Work

Chapter Three

low stakes slot machines

“Know your enemy.” – so said Sun Tzu in The Art of War, which he penned more than 2,500 years ago. Calling the slot machine your enemy might sound counter productive to the superstitious amongst you – after all, surely you want it to be your friend and pay out lots of lovely money.

But the point of Sun Tzu’s words is that whether you are going up against the Mongolian Army, the blackjack dealer, the roulette wheel or the slot machine, you stand a better chance of winning if you understand who or what you are facing and what makes it tick.

Programming the reels

One of the questions I am most often asked when it comes to slots is how on the one hand a machine can deliver random results but on the other it is programmed to provide, let’s say, a 90 percent payout.

To find the answer, we need to think about that roulette wheel again. Remember, for a straight up, you are being offered a 35/1 payout on what is actually a 36/1 shot when you play on a single zero table. The reel on a slot machine is not so different to a roulette wheel, and the principle works in exactly the same way, calculating the payout as a function of the actual likelihood, in order to deliver the desired percentage over time.

If you are still scratching your head, let’s start by looking at a basic, old fashioned, mechanical slot machine in its simplest form.

Our hypothetical machine has three reels and four symbols, let’s call them Bell, Bar, Cherry and Orange. Bell is the jackpot, so three bells is the best you can get. Next best payer is the bar, then cherry, then orange.

The probabilities are adjusted by each reel actually having ten symbols on it. So each has one bell, two bars, three cherries and four oranges. 1+2+3+4=10. OK, with me so far? That’s great.

To dip back into the maths again for a moment, you have ten possible positions in which each reel can stop. With three reels, that means the total number of possible positions in which the reels can stop is 10x10x10=1,000.

Of course, with the repeated symbols, that does not mean there are 1,000 different possible outcomes.

Let’s say the machine pays out for three of a kind and nothing else. Here are the probabilities, or odds, if you will, for each:

Three Bells: 1x1x1 = 1 – so there is a one in a thousand chance, or 0.1 percent

Three Bars: 2x2x2 = 8 – so 0.8 percent chance

Three Cherries: 3x3x3 = 27 – 2.7 percent chance

Three Oranges: 4x4x4 = 64 – 6.4 percent chance

Conveniently for our purposes, 1+8+27+64=100, meaning 90 percent of the time, the spin will not result in a win.

All clear so far, I hope. The next question is how to set prizes to get the payout percentage the casino or machine owner wants?

To find the answer, we have to look at how many coins are paid out for every thousand that are put in. I am saying per thousand instead of per hundred to keep the maths easier – you will see why as we work through it.

For every thousand coins fed into the machine, the true odds are that three bells will come up once, three bars will come up eight times, three cherries 27 times and three oranges 64 times. The other 900 times, a mixture of symbols will come up. Let’s say the machine is £1 per spin and we will try plugging some winnings in.

How about a jackpot prize of £150 for three Bells, then £20 for three bars, £10 for three cherries and £5 for three oranges. Would that tempt you to play? Let’s see how that pans out in terms of a payout percentage.

Three of a kind PrizeEvents per 1,000 spins
Total payout per thousand spins


So there you have it – in this scenario, the reels can roll at random, and by having these prize amounts, the machine actually has a payout rate of 90 percent. Or if you prefer, a house edge of 10 percent.

Just to play with the numbers a little more, suppose the jackpot for three bells was raised to £170, and the prize for three bars to £30. In that case, the total payout for every thousand pounds put in would be £170 + £240 + £270 + £380 = £1,060 and the machine would be running at a slight loss.

To go the other way, if the jackpot was £100 instead of £150, and the other prizes remained at £20, £10 and £5, you can see that the payout percentage drops to 85 percent.

Of course, today’s slot machines do not consist of three reels and four symbols, but the principles we have applied above carry through. It is just the maths that gets harder, but that’s what we’ve got computers for, and now that you have the underlying concept nailed down, we can let them worry about the probability theory going forward.

Pause for thought

Let’s just think for a moment about how modern machines differ from the above example – in fact, why don’t you have a little think while I get a cup of tea, and we will see what you’ve come up with. Take a minute, then read on.

low stakes slot machines

Modern slot machines

Ready? OK, here’s what I have on my list of how modern machines differ from the above example. What did you think of?

  • They have more than four symbols
  • They have more than one payline
  • They pay out on more combinations than just three of a kind
  • They have more than three reels
  • Hold and nudge options can alter the odds
  • Bonus events and side games can alter the odds

So let’s see how that affects things by looking at a standard modern day slot machine – nothing over fancy, just something you are likely to see in a casino, a pub or maybe down at Southend seafront.

Super Jackpot Party was one of the first video slots to become widely available, so it holds a special place in many hearts. Let’s use it as a case in point to examine the additional complexities we mentioned.

Here, there are five reels instead of three and eight different reel symbols that can form winning combinations, instead of four. Then, you also have the party guy and noisemaker symbols, which launch the bonus game.

The bonus game in itself has a bearing on the overall odds of winning and therefore needs to factor into the mathematics to get the overall return right.

Prizes are awarded for matching three, four or five symbols, meaning suitable payoff values have to be calculated for a far longer list of potential outcomes than the simple £150, £20, £10, £5 we used above. On top of that, the multiple paylines have the effect that even if there is only one of each jackpot symbol on each reel, they could all match up on any one of the paylines.

Of course, when I talk about numbers per reel, I now mean that figuratively rather than literally. Super jackpot party doesn’t have physical reels rolling around inside it any more than the odometer does in your modern car. The same effect, however, is created digitally, using a random number generator. Let’s look at that next.


Random number generators lie at the heart of almost any online game you might play, be it a slot machine, a game of roulette or even blackjack. But they have been around since before the internet came about and allow machines like Super Jackpot Party to handle the additional levels of complexity we just described.

After all, with a physical reel, you could conceivably have 20 symbols instead of 10. Perhaps even 30. But any more than that, and the reels would look like one of those water wheels in a mill, and the machine would be the size of a house.

With a random number generator, you can have the equivalent of 1,000 symbols per reel if you wish, but let’s imagine a simplified version, just to get the idea across.

We will use the same four symbols, but this time, let’s have a virtual reel with 50 stops instead of 10. We could have one bell, six bars, 15 cherries and 28 oranges. All we need to do is allocate the random numbers of 1-50 accordingly.

So according to our random number generator, it could go like this:>

1 = Bell
2 to 7 = Bar
8 to 22 = Cherry
23 to 50 = Orange

Let’s see how that changes things for the “three of a kind” options. The first thing you will notice is that instead of 1,000 possible outcomes, we now have 125,000, which is what you get if you multiply 50 by 50 by 50.

The second thing you will notice is that the possibility of three Bells is still just one, so the odds have gone from one in 1,000 to one in 125,000. This immediately suggests a potential for a bigger jackpot. Let’s look at the full results, comparing the possibility of three of a kind per 1,000 spins in the original scenario with the possibility per 125,000 spins on our virtual reel.

Three symbols Per 1,000 spins
Per 125,000 spins

Of course, you can also have added complexities worked in, such as blanks and bonus game symbols, but even with the (relatively) simplified representation above, you can see that by having 50 or 100 or 1000 stops on your virtual reel, it gives casinos the possibility to offer a far larger jackpot.


In our 10-stop scenario, we had a jackpot of £150. I’m not saying we wouldn’t like to win that, but now, you start to get an inkling of how that famous machine in Vegas was able to pay out almost £40 million, while staying within the constraints of its programming for the house edge.

In our simplified example, let’s see what kind of jackpot we can offer now. Again, we will keep the payout percentage at 90 percent. Given that the probability of three oranges has almost trebled from 6.4 percent to 17.5 percent, let’s reduce the prize on that from £5 to £3. We will leave the prizes for three bars and three cherries as they were. Let’s see what effect that has on the jackpot.

For a 90 percent payout percentage, we will need to pay £112,500 per 125,000 spins.

10-stop prize 50-stop prizePayout per 125,000 spins
Three bells£150£???£???
Three bars£20£20£4,320
Three cherries  £10£10£33,750
Three oranges  £5£3£65,856


You can pull out your calculator to work it out if you like, but I can tell you that when you do so, you will see that the casino can now offer a jackpot prize of more than £8,500. Drop the prize for three oranges to £2 instead of £3 and the jackpot can be in excess of £30,000.

Immediately, you can see that the relatively minor increase from 10 to 50 has led to a massive increase in the possibilities. Of course, you can change the way the 50 random numbers are allocated, too. Go ahead, get out a sheet of paper and a calculator and play around with it.

The interesting thing to keep in mind is that despite the big difference in the jackpot, both of the scenarios we have been through result in the same 90 percent payout percentage, so a casino could actually have two slot machines set up exactly as we have described, and it will make exactly the same return from both of them in the long run.

Strategic Slotting

Chapter Four

low stakes slot machines

When it comes to slot machines, many supposed experts will tell you that it is all down to luck. They will say that if you are playing poker or blackjack, you can play strategically and improve your chances of success. But aside from some skill based components to the bonus games, there is no skill or strategy that you can follow when playing on a slot machine.

What complete and utter poppycock. If you are playing blackjack, there is more to strategy than knowing whether to hit or stand. There is also the question of how much to wager and whether to play on or walk away, and these are equally important strategic decisions on the slots.

The thought on which we concluded Chapter Three is an interesting one from a strategic perspective, too, and it is worth us chewing it over for a few minutes. Your average casino, amusement arcade or even pub will probably have a whole line of slot machines. Let’s pretend for a moment that it includes the two we imagineered in the last chapter, which both have a payout percentage of 90 percent. And let’s say it has a couple more that pay out at 86 percent, and one that pays out at 92 percent.

The point is, you won’t know that. All you will know about the payout percentage is that it is greater than 80 percent, and probably around 90. You can be sure of that – today’s machines are subject to rigorous checks and audits. Believe me, even if the casino owner was a complete crook, it wouldn’t be worth the risk of doctoring the machine, as the potential consequences could mean the end of his business. 

The other thing you won’t know is the odds. In our examples above, one of the machines has a one in a thousand chance of hitting the jackpot, the other is a one in 125,000. 

But something you do know is the pay table, as that will be written on the machine. This will give you some clues as to machine volatility and that in turn can guide your decision making as to where to place your coins. 

A few words about volatility 

Notice the enormous difference it made to the jackpot potential in the previous chapter when we changed the award for three oranges from £3 to £2 on the second machine. Well, this can be even more pronounced as machines get more complex.

To sum it up into a rule, it is fair to say that when the jackpot is big, the lower prizes are usually smaller, and when the jackpot is smaller, the lower prizes are more generous. These are known as high volatility and low volatility machines respectively.

So if your aim is to win millions and retire to Tierra del Fuego, you will be looking for a high volatility table. But be prepared for the fact that there is a greater likelihood of the machine simply swallowing your bankroll and giving little or nothing back.

If, on the other hand, you are in it for the joy of the game and want your money to last longer, a low volatility game, with a less impressive jackpot but more frequent small paybacks, is just the thing for you.

Frequency versus payback

Looking at our two machines again, which would you choose to put your pound in? All that you would know from looking at them would be that one pays out £150 jackpot and the other pays out £8,500. You might also pay attention to the fact that the second one pays £3 for three oranges compared to the first one paying £5, but that would not be a major factor.

What you would not know is that they both have the same payout percentage. The other thing that you would not know is that the second one has almost double the payout frequency. If you remember, in the case of machine one, 900 times out of 1000, it would not have three of a kind so it would not pay out. In other words, the payout frequency was 10 percent. 

In the case of machine two, thanks to all those oranges, the payout frequency is 20 percent. Observe the two machines for long enough, and you will soon pick up on the fact that the second one spits out a couple of pound coins far more often than the first gives away anything. 

Can you believe the pay table?

Unfortunately, not every machine that has a higher jackpot is also going to be so kind as to give more frequent payouts than its poorer neighbour and at the same time have the same payout percentage.

To illustrate the sort of elephant trap you might come up against, take a look at these two machines I have prepared for you. As usual, they are very simple ones that simply have Bell, Bar, Cherry and Orange. I’ve got the pay table right here. Which one will you put your pound in, A or B?

Prize for three of a kind Machine A Machine B
Bell £1,500 £1,000
Bar  £150    £100
Cherry £20  £10
Orange £2 £1

 Take your time, there’s no trickery here. Which will you choose? 

I know that you are dying to say Machine B, because you know I’ve got something up my sleeve, but you have to agree with me that on the face of it, Machine A looks the more tempting, because for a £1 wager, you have a larger jackpot. In fact, you have larger pries all the way down.

OK, now let’s take the cover off the machines and I will show you the hit frequencies. Both are set at hits per 10,000.

Hit frequency Machine A Machine B
Bell 1   1  
Bar 25 30
Cherry 150 300
Orange 350 2000

This puts a different complexion on things. Let’s finally look at the payoff per £10,000 poured in, by multiplying the prize by the frequency: 

Payoff Machine A  Machine B
Bell  £1,500 £1,000 
 Bar £3,750   £3,000
Cherry   £3,000  £3,000
 Orange  £700  £2,000
Total   £8,950  £9,000

We can see that while Machine B has a payout percentage of 90 percent, just like our first two machines, Machine A has a slightly poorer percentage of 89.5 percent.

So in this case, your instinct not to trust the pay table was absolutely right – you are better playing on Machine B.

Video Slot Machines

Chapter Five

Take a trip to Vegas, and you will still see plenty of the old fashioned slot machines with Bells, Bars and the rest, and nothing else. Some of them even have the traditional “one armed bandit” style lever.

But they will be outnumbered by video slots, like our old friend Super Jackpot Party, and if you walk into a casino or arcade in the UK, this is the sort of machine you are almost certain to encounter today. They bring an added level of complexity to gameplay, but that also makes for a richer experience. Here are some of the features they include. 

Progressive Jackpots

Progressive jackpots

This adds a frisson of excitement to the proceedings. You will see a screen prominently displayed above the machine showing a steadily rising jackpot. Of course, this gives players the mistaken impression that the higher it rises the more likely it is to pay out. From all that has come before, you will realise that things don’t quite work that way, but it still makes for an exciting extra.

Multiple bonus events

We will talk about bonus games in more detail in a little while, but it is worth mentioning here that some video slots include more than one bonus event.

Video Slot Themes

One of the difficulties that marketers have had with slot machines is finding something other than the jackpot amount to differentiate theirs from all the rest in the arcade or casino. We found this to a certain extent earlier – I lined up four machines for you and asked you which one you wanted to put your pound into, but all you had to go on was the pay table. 

video slot machine planet of the apes

If instead I presented you with four machines featuring The Simpsons, The Walking Dead, Sonic the Hedgehog or Escape from Alcatraz, it would give you a little more food for thought. This has become a particularly important differentiating factor with online games. 

Special effects

The themes don’t just involve musical effects, decorated machines and related bonus games. Did you ever see the Top Gun slot machine? It was a remarkable piece of kit, more akin to the cabinet games in arcades where you can sit in a racing car. In this case, it was a fighter jet, and you would take the pilot’s seat and shoot down the bonuses.

Multiple lines

While you might say that some of the above factors are gimmicks, an aspect of video slots that has a fundamental impact on your gameplay is the possibility to play multiple paylines. 

With, for example, three paylines across five reels, there are far more complex combinations possible. Again, this has the potential to cater for both high and low volatility. On the one hand, machines might pay out on three matching symbols, even if they are spread across paylines, providing frequent small payouts.

In fact, many of the most recent machines have a payout frequency of more than 50 percent. However, most of these payouts are very low, even less than the original stake. A typical example of pandering to 21st century attention spans and keeping people interested with the sound of coins dropping? You might well think that, I couldn’t possibly comment.

At the same time, however, the possibility of the elusive jackpot five bells in a row becomes even more improbable, perhaps millions to one, suggesting that awe-inspiring multi million pound payout can realistically be offered. The point is, we have now evolved from three reels of 10 to the electronic equivalent of five reels of 100.

How is your maths? If we keep the ultimate jackpot at five bells, and there is only one per virtual reel, then with one payline, the odds are ten billion to one. Even with ten paylines, that only brings it down to a billion to one. Now do you see how that $40 million payout came about?

The point I want you to understand is that greater complexity, additional paylines and higher random number generations all add up to more choice and flexibility for you. Those frequent small value wins result in a low volatility game that can hold your bankroll intact for longer and keep at the machine for hours. Conversely, putting a higher proportion of your returns into bonus games or making higher value punts on multiple lines can mean higher volatility, leading to a chance of big wins, but also a faster drain on your finances.

Understanding these different nuances puts you in control, and allows you to play the game on your own terms.

Bonus Games

Chapter Six

slot bonus games

Mention bonus events, and you probably think of an impromptu game of snakes and ladders, Play your Cards Right or some bizarre escapade involving Bart Simpson and a radioactive donut on the upper screen. The point is, it is a game within the game that can be accessed by achieving a certain combination on the slots. The concept is older than you think, however. I’ll walk you through some of the most well known ones. 

Winner spinners 

Back in the 1980s, there was an extremely basic slots game for the Spectrum and Amstrad home computers. I think it was imaginatively named Fruit Machine

Even that had a bonus feature, called a “winner spinner,” and the concept derived from the mid 20th century, when mechanical machines would have a wheel (picture the “wheel of fortune” on TV) fixed to the top of the machine. A spin on that would result in you winning the indicated amount.

These days, you still see bonus wheels, although they are more complex, and often you will spin them to win something other than free credits – you might win some time on a bonus event, or perhaps the spin will decide the bonus event you get to play.

Anyway, whatever you are spinning for, the principle behind it is absolutely identical to that of the slot reels. To understand how it works, let’s take a really simple wheel of fortune, split into eight segments. Each segment contains a prize amount of, let’s say, 5, 10, 25, 50, 100, 150, 200 and 500.

With equally sized segments, you might think the probability of hitting each segment is equal, ie one in eight or 12.5 percent. If I asked you to tell me the average payout, you would probably add the eight prize amounts together and divide by eight, arriving at an answer of 130. 

However, the reality is that the machine will be set to pay out the 500 jackpot far less often than the others. Again, it will not be fixed in any dishonest way – it will simply use a random number generator to set the probabilities and odds. 

In this case, let’s say it picks a random number between 1 and 50, where the numbers are allocated as follows:

Random number  Bonus payout Probability 
 500  1 in 50 = 2%
2-3   200  2 in 50 = 4%
 4-6  150   3 in 50 = 6% 
 7-10  100  4 in 50 = 8%
 11-21  50 11 in 50 = 22% 
 22-32  25  11 in 50 = 22%
 33-43  10  11 in 50 = 22%
 44-50  5  7 in 50 = 14%


Here, you can see that the wheel is designed to pay out at the 10, 25 or 50 level two thirds of the time. It will only pay out the 500 on one spin in 50, not one spin in eight as it might appear.

This works out at an average payout of just over 50 per spin, far less than the 130 we initially thought.

It is interesting to note that the weighting will typically go light on the lowest value – the 5 will come up on only seven spins in 50. This is so that players will not get overly discouraged, and will keep playing the game. After all, a 20 or a 50 is pretty good.

The other point worth bearing in mind is that modern digital machines have all sorts of variations on the old wheel of fortune. There are discs you can spin and tumblers you can roll using touch screen effects. You can even dictate the speed of the spin, giving the impression that you are in complete control. In the end, it all comes down to that random number generator, though.

Free spins

An even simpler form of bonus is the free spin. This doesn’t demand any extra screen or complex gameplay, and at its most basic, it simply uses the same reels as the main game. All they require is some extra, or special, symbols incorporated into the reels.

They are often a feature of the lower denomination games. Over the past few years, the 1-cent games in the Vegas casinos have become among the most popular, but substantial payouts are always going to be very few and far between. Free spins are a great way to keep players interested and at the machine for longer.

The beauty of free spins is that they act as a bonus in themselves – as they appear on the machine heralded by a cacophony of light and sound, you already feel you have won, and that you are effectively a pound up, or whatever the spins would have cost you in coins. They also give you the chance to win big, or indeed small, when you take your spins. In general, free spins pay out on winning combinations in exactly the same way as regular spins.

Pick ‘ems 

Another ever-popular bonus type is the pick ‘em bonus. These first appeared in the 90s with the rise of video slots. In our favourite example of Jackpot Party, you can keep picking boxes that contain different prizes. When you select the box with the “party pooper” booby prize, the bonus round ends and you are back to normal gameplay.

Here’s a quick mid-term test for you. How do you suppose the content of the box is dictated? Yes, you’ve got it, it’s another random number generator. However, there is no trickery going on. Some people ask me whether it actually makes any difference which box they choose of balloon they pop or whether the prize they will win is predetermined.

The answer is that it does make a difference. The prizes really are put in the boxes, in a digital sense, and you have a chance to choose the right one, or crash and burn from the start.

Suppose there are ten boxes to choose from, and the possible outcomes are 5, 10, 25, 50, 100, go again and the booby prize. They might be set against a random number set of 1-50 in much the same way as the wheel of fortune in our previous example. The RNG will then randomly pick ten numbers and hide your prizes in each box. The lower wins, along with the go again and the booby prize will be more likely to appear than the high prizes, but it really is down to luck.   

As the years have rolled by, the pick ‘em type bonus events have risen in popularity as they are so versatile for every theme of game. One of the most famous is the “Deal or No Deal” game, based on the TV show. It is immediately evident how well this sort of game, with its briefcases containing different cash amounts, lends itself to this type of format. And not a Noel Edmonds in sight!

Skill based bonuses

While classic bonus games involving spins of one sort or another and pick ‘ems are still a mainstay of slots, take a stroll round any casino and you will see an increasing trend towards more complex bonus events.

There is a regulatory reason behind this, and it all begins in Vegas. Till recently, the Nevada Gaming Commission stated that no more than four percent of a game’s payback could be skill based. That wasn’t enough to give players any meaningful opportunity to nibble away at the house edge through skilful play in the way that you can at, for example, a game of blackjack.

However, in 2015, the rules changed, and fully skills-based gambling was permitted. Why does this affect us at our local UK casino or in the amusement arcades at Southend seafront? Well, Vegas is obviously one of the main markets for slot machine manufacturers. The change in the rules will mean they will be coming up with all sorts of new ideas to make their games more interesting and competitive. You can be sure they will be marketing these globally and not just in the USA. 

So what skills based games do we already have, and where might this sector be heading? The earliest versions featured video versions of simple arcade classics, such as Snake, Pong and so on. The idea was straightforward enough – get a winning score in the game and you get a bigger bonus.

Other examples take a scenario that might give the illusion of being skill based, but is effectively down to luck – variations on the “snakes and ladders” theme that involve the roll of virtual dice are a good example here. Effectively, these are just refinements on the winner spinner theme we discussed at the beginning of this chapter. 

The development of the skill-based side of bonus games in slots is likely to be the biggest change since the introduction of video slots in the 1990s, so there are exciting times ahead. 

Mystery bonuses

In most cases, you know what has to happen in order to get going on the bonus event. Typically, it requires hitting a certain icon on the reels, or perhaps building up some lights on an accumulator.

On some games, though, you never know when the bonus is coming. This makes for a great feature, lending some mystery and excitement to gameplay. As usual, this is also down to those random number generators. Sometimes they have to hit a certain combination that would not be obvious to the player, while other times, it will be either after a preset period of time, or perhaps when a certain amount of money has been paid into the machines.

Impact of bonus events on payout percentages

We have chatted for a while about the bonus games, and I think you will agree that they form one of the most important aspects of slots, and one that is set to become even more significant over the coming years. After all, the nature of the bonus event is one of the biggest differentiating factors between one machine and the next.

Also, judging by the change to the laws in the USA, skill based bonuses could seriously rock our ability to influence the house edge in the years to come, something that has never happened before since those first machines at the end of the 19th century.

With this point in mind, it is worth sparing a moment to think about how bonus events currently influence payout percentages.

At present, the bonus events are almost entirely determined by the random number generators that run every other aspect of the machine. As such, they simply form a part of the complex programming that we simplified and picked apart a little bit in previous chapters. The mathematics are set in stone and everything is optimised to ensure the payback percentages are what they are supposed to be.

Come and talk to me in a couple of years, though, and we will see how the increase in skills-based bonuses has the potential to upset the apple cart. It could be that I will have to add some new chapters to this guide, offering strategic advice on specific bonus games and telling you how the best players can increase the payout percentage from 90 percent to 95. As I said earlier, these are exciting times, so watch this space.

The Rise of Online slots

Chapter Seven

low stakes slot machines

Speaking of technological innovations, there has been another one going on over the past few years that you might just have noticed. These days, everyone has a smartphone, even me. We are constantly online and reachable, which I would have considered a disaster in the 1970s and 80s, but that, as they say, is another story.

What is relevant to our discussion here, however, is that the internet and the dawn of the smartphone generation has given rise to an explosion in online casinos and gambling.

Given everything I said earlier about the sight, smell and atmosphere of a casino or arcade, you might assume I am not a fan of online slots, but nothing could be further from the truth. Physical slot machines are always going to be around, at least for as long as I am, and as far as I can see, the online versions simply provide an extra playing option for enthusiasts.

There is also no doubt that they bring slots to a wider audience. There are some poor souls out there who are not in the habit of visiting casinos, pubs and arcades. Quite what they do with their lives to fill those hours is a mystery to me, but it is up to them. My point is that online spots allow you to have a little wager on your favourite game wherever you are and however much time you have to spare, and that can’t be a bad thing. 

Do online slots differ from real slots?

Conceptually, an online slot machine is going to be exactly the same as a physical one. It uses the same RNG, and probably even exactly the same programming as the machine. The only difference is that it is running on your smartphone or computer instead of inside a physical cabinet, and you put your money in using online transfers from your account.

What about payout percentages?

Here’s an interesting thing. While I have said that the programming is often identical online and in a physical machine, this is not always 100 percent the case. One difference you might encounter surrounds the payout percentage.

I mentioned earlier that casinos have to pay salaries, electricity bills, business rates and all manner of other overheads, and then deliver a tidy set of financial results to their shareholders every year. Online casinos have costs, too. And they want to make money. But their overheads are far lower, meaning they can often operate comfortably with a lower house edge.

It gets better, too. As you might have noticed if you have switched on your television of an evening, the market is incredibly competitive. There are literally hundreds of online casinos out there, and they all want your business. Typically, they also generate advertising revenue from various sponsors, and, understandably, this increases if they have more members and traffic.

For this reason, there have been instances of some online casinos operating with a negligible or even zero house edge. Will this prove to be sustainable? Time will tell, but my advice to you is to make hay while the sun shines. 

Online games 

In general, you will see the same games online as you see in the arcade or the casino. Our old friend Super Jackpot Party is there, of course, along with games such as Golden Goddess, Cleopatra and Rainbow Riches. These are worthy of mention, as they are specifically aimed at the female market.

Does this mean we are going full circle, and the online casinos are targeting the ladies to “keep them amused?” Not really. It is simply a matter of economics and responding to the reality that well over 50 percent of online gamers are female. If your image of a “gamer” is a spotty teenage lad hiding away in a darkened room playing Dungeons and Dragons, you are clearly as stuck in the 1980s as much as I am – no wonder we are getting along so well!

Any downsides

From what I have said so far, the online option certainly sounds like a winner, doesn’t it? You don’t have to venture out, the house edge is lower, oh, and all of them will offer you a pile of free spins of bonus credits on your account as a welcome offer. 

So what’s the catch, you might ask. To be frank with you, there isn’t one. Years ago, people worried that the games were fixed, or someone was going to hack into their account and steal all their money, or things of that sort. In the 1990s, when the internet was a little like the wild west, they might have had good reason for their concerns. 

Today, though, the online casinos are as carefully monitored and regulated as the physical ones – often more so. Also, they are operated by serious companies that are major players in the industry. These global corporations place integrity and trust above all else. In other words, there is neither the opportunity nor the driver for anyone to seek to fleece, defraud or rob you.

The only potential issues you might encounter are logistical ones. Make sure your internet signal is tip top before you begin – I can’t imagine anything worse than being disconnected mid-spin – and read all the fine print so that you are 100 percent clear on how you put money into, and take it out of, your account. 

Also, be aware of how the joining bonuses work. If a casino adds £10 to your credit, you clearly have to use that for spins. You can’t just withdraw it, that would hardly be fair. Most ask you to reinvest that “free money” a set number of times before you can take it out.

low stakes slot machines

In Conclusion

Slot machines are part of our social landscape in the UK. They are something we have all seen from time to time, and almost every one of us has put the odd 20p or pound coin into one over the years.

For the uninitiated, those “slot machine experts” can look like people with almost mystical skill and knowledge that must have been acquired over many years.

In my case, the “over many years” bit is certainly true, but when my eyes were opened to the truth, the biggest discovery was that there was nothing mystical to it at all – win or lose, bonus spinner or party pooper, it all comes down to mathematics in the end.

We have talked about the earliest slots, the rise of video slots and the impact of the mobile and online revolution. We’ve even taken a peep into the crystal ball to see how slot machines are likely to evolve over the coming years, and the future looks like a very interesting place.

As a parting note, though, I will return for a moment to those childhood days in sunny Southend. I took a drive there last summer, and I’m delighted to be able to tell you that the Kursaal is still standing, and looks like something close to its days of old after falling into disrepair in the late 1990s.

Even better news is that the Happidrome Arcade is not just still there, it is looking better than ever, having undergone some renovations following flood damage in 2015. OK, so the place doesn’t smell of stale cigarettes any more, but you probably won’t think that a bad thing.

Do give it a look if you find yourself in that part of the country, and when you do so, half close your eyes and you might see the ghost of a kid from years gone by, flitting between the old-style fruit machines.

I hope you have enjoyed this affectionate look at the world of slot machines from someone who has been there and done it. Good luck, and enjoy the game.

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