Are Slot Machines Random

  1. Modern slot machines use a random number generator to determine their results. This is a computer program that generates thousands of random numbers per second, each of which is tied to a particular result on the reels.
  2. The gameplay is just as you’d expect for a fruits slot machine but with Random Runners, you don’t just get one set of reels, there are two. And it’s this twin action with synchronised spinning which really sets it apart from the pack. The symbols you’ll be spinning are the fruits which you’ll be very familiar with.
  3. Whenever the slot machine is turned on, the random number generator is spitting out whole numbers (typically between 1 and several billion) hundreds of times a second. The instant you pull the arm back (or press the button), the computer records the next few numbers from the random number generator.
  4. If the results are truly random, people argue, then the payback should be random too. Despite the fact that this governor function does not exist and in all jurisdictions whose regulations I’m familiar with, it is possible for the results on slot machines to be determined at random and for machines to have specific payback percentages.

By John Robison

One of the questions I'm asked most often is - 'how is it possible for a slot machine to be a random device and for a machine to also pay back a certain percentage of the money played throughit?' If the results are truly random, people argue, then the payback should be random too.

The Random Number Generator. All Slot machines contain a 'random number generator' (RNG) is a microchip that constantly (even while the machine is standing idle) generates combinations of numbers.

Despite the fact that this governor function does not exist and in all jurisdictions whose regulations I’m familiar with, it is possible for the results on slot machines to be determined atrandom and for machines to have specific payback percentages.

It’s difficult to reconcile the fact that results on slot machines are random and for us to be able to know what will happen overall on amachine. Let me illustrate how this is possible with my RWB Ping Pong Ball Game.

Suppose I have a basket that contains 100 ping pong balls. Eighty ping pong balls are white, 15 are blue, and five are red. You draw a ball at random from the basket. There’s acover on the basket, so you can’t tell what color ball you’re drawing. Also, you can’t tell the balls apart, so you’re no more likely to draw one ball over any other. After you drawthe ball, you record the color and put the ball back in the basket.

As you repeat this action, you will find that the percentage of draws that were red balls gets closer and closer to 80%, the percentage of draws that were blue balls gets closer and closer to15%, and the percentage of draws that were red balls gets closer and closer to 5%.

We know that this will happen because you draw the balls at random and each ball is equally likely to be drawn by you. But it is not equally likely that you will draw any particularcolor. Eighty percent of the balls are white, so we expect 80% of your draws to be white. Similarly for the blue and red balls.

Even though you drew the balls completely at random, the distribution of colors you recorded will match the distribution of colors in the total population of ping pong balls in thebasket. Random does not mean that everything is completely unpredictable and unknowable.

Now let’s make the game more interesting. You have to pay me $1 each time you want to draw. When you draw a white ball, I keep the dollar. When you draw a blue ball, I return your dollar.And when you draw a red ball, I pay you $16. A nice payoff for drawing the red ball.

Looking at this game from my perspective, I have a 15% chance of paying you $1 and a 5% chance of paying you $16. Calculating this out, we have 0.15(1) + 0.05(16) = 0.15 + 0.80 =0.95. On the average, then, for every $1 you give me to play, I will return 95 cents to you.

The RWB Ping Pong Ball Game is just like a 95% payback slot machine. Even though the outcomes in both games are chosen completely at random, each pays back 95% of the money played in the longrun.

A slot machine works very much like the RWB Ping Pong Ball Game. Conceptually, there is a basket of ping pong balls for each reel. But instead of having different colors on theballs, these balls have symbols representing the different symbols on the reels on them. Some symbols appear on more balls than other symbols.

Let’s set up a basket of ping pong balls for a reel from a real Double Diamond slot machine. Even though there are 22 symbols and blanks on the reel, our basket will have 72 ping pongballs in it. Having more balls in the basket than we have stops on the reel allows us to alter the probability of landing any particular symbol on the payline from what it appears to befrom counting the number of times it appears on the reel and dividing by 22.

The reel has 11 blanks on it, but I’m going to put 31 blank ping pong balls in the basket. Half the stops on the physical reel are blanks, but slightly less than half the ping pong ballsare blank, so it’s actually a little less likely than it appears for a blank to land on the payline on this reel. There’s only one cherry on the reel, but I’m going to put two ping pongballs with cherries in the basket.

All of the other symbols – single bar, double bars, triple bars, 7, and Double Diamond – appear twice on the reel, but the number of ping pong balls with each symbol in the basket is 25,4, 6, 2, and 2, respectively. We need about 6.5 ping pong balls with each of these symbols in the basket to have the probability of drawing a ping pong ball carrying the symbol be thesame as what appears to be the probability of having the symbol land on the payline from looking at the reel, so you can see how different the true probabilities are from what the reel makesyou think they are.

Just as with the RWB Ping Pong Ball Game, the more you play this Double Diamond machine, the closer the distribution of symbols landing on the payline will get to the distribution of ping pongballs with each symbol in the basket.

Even though it sounds like random should mean completely unpredictable, the only thing we can't predict is what color ping pong ball you'll draw next or what symbols will appear on the paylinenext. Because we know the distribution of ping pong balls in our basket and the casino knows the distribution of symbols on the slot machine's reels, we can predict -- no, more than predict, wecan calculate with near certainty -- how much my game and how much a slot machine will pay back in the long run.

The only reason we can't be dead certain of how much a machine will actually pay back is because the outcome of each game is truly chosen at random and there is no function forcing the paybackto a particular number. But given enough draws or spins, my RWB Ping Pong Ball game and a 95% payback slot machine will both pay back very, very, very close to 95%.

To sum up, there's no attempt in the programming of a machine to force it to a particular payback percentage. There’s no need to. Random sampling from a known population takes care ofit automatically.

Send your slot and video poker questions to John Robison, Slot Expert™, at [email protected].
Because of the volume of mail he receives, John regrets that he can't reply to every question.

Synopsis: Are slots really random? Explanation on why slot machines are not quite as random as both land based and online casinos say they are.(1)

Author: Jungle JimContact: Disabled World

Published: 2014-03-11Updated: 2020-06-23

Key Points:

Are slot machine payouts really random?

Are all slot machines rigged as to when they payout to the player?

Main Digest

Please note that the article below is my opinion only, from what I have experienced from playing slots, both at land based casinos, and several different popular online casinos - all of which shall remain nameless.

Playing slots, pokies, fruit machines, one arm-bandits, poker machines, whatever you like to call them, depending on where you come from, is a popular pastime for many seniors and retired singles and couples.

Are Slots Really Random?

What Casinos and Slot Machine Technicians Will Tell You:

Online casino slot games are said to use the same kinds of random number generator programs as land-based casinos. They just serve up your results via animation that is sent to your computer via the Internet.

Casinos will often tell you that slot machines use a computer to generate random numbers, and these determine the outcomes of the game. When players press the 'Play' button, the machines computer generates what is known as a RNG, a gaming term that is an abbreviation for 'random number generator'. Random number generators (or pseudorandom number generators) are special algorithms that are used in computing when an outcome needs to be as random as possible.

  • When the play button is pressed the RNG randomly selects a winning or losing combination from among millions of available combinations.
  • Slots don't get hot or cold - Slot machines are said to have something in common with goldfish: they have no memory. Every spin is independent of the prior and/or following spins.
  • Every spin is considered to be a brand new spin, with any possible symbol combination outcome.
  • Slot players are said to either win or lose; they never 'maybe win' or 'maybe lose', or never 'almost win'.

Slot machines often display a series of spins where players appear to be only one symbol away from a win, therefore leading them to falsely believe that they almost won. Slot games do not work on any kind of cyclical basis - and slot machine jackpots don't become due.

I call BS!

Are Slot Machines Random

Why I Believe Slot Machine Games are Not Random

Slots are not random and I will never be convinced otherwise, I have been playing slots for many years and seen so many different examples of them being NOT random, making it incredibly difficult to believe that slot machines are totally random, here's why:

  • If slot machine games are designed to fit into a maths model, which they are said to be, then they cannot be TRULY unpredictable.
  • I have played certain online slot machines where the 'Payout' or money won amount is displayed BEFORE the bonus game spins end.
  • How is it possible for a slot machine to be a random device and for a machine to also have to pay back a certain percentage of the money played through it?
  • Anyone who's played certain slot machines for example, could not fail to notice how you don't see ANY certain symbols on the reels for ages, then suddenly they are everywhere!
  • It often feels almost as if there is some algorithm at play preventing a certain feature to happen too soon after starting a slot game, and only happening once you've lost enough money to cover the feature's payout.
  • Have you ever been steadily winning playing a certain amount, e.g $1, so you decide to bet more to win more and increase your bet per spin to $2. What happens? The machine 'instantly' stops paying and becomes deader than a Dodo bird! Strange isn't it, considering slots are supposed to be so called 'random' (sarcasm).


Screenshot of the Mad Mad Monkey online slot game.

On some progressive jackpots linked to a bank of slot machines, the jackpot has to be won before a certain amount of money is reached. Now, if this is the case, how are they REALLY random if they have to hit before the jackpot reaches a certain amount? Totally random means they can hit at ANY time. If they have to hit by a certain amount they have to be programed to do that.

I was once asked in an 'anonymous' online casino survey, 'If I felt like I received enough playing time for the amount of money fed to the slot machine!' Now, why ask something like that if it is beyond their control to 'adjust the settings'? Was it because if a player was losing their money too quickly - resulting in a shorter machine play time - then the machine would 'compensate' by paying out more before the end of the playing time? This time of play adjustment would then allow casino patrons, both on and offline, to 'feel' they had value for money due to the adjusted extension of playing time on the machine.

Losing on One Machine - You'll be Losing on All Machines!

Are Slot Machines Programmed Or Random

What I don't get, if you have a win on one particular slot game and then move onto several others, they will all be dead. For every win I have had I then lose constantly until the money I won and some has been played back, no matter what slot I play before I even begin to get above my deposit back again - it is the same pattern each time and that does not appear random to me. It's as if all the online slot machines are linked to a central computer - For example: If you are continually losing, when playing online slots, switching to another slot game doesn't matter as all the games you try do not payout as well. The only so called random thing is if your players account has been deemed worthy of a win for a change. It would be extremely easy, and fast being a computer, for a 'central computer' to check the deposits, as well as wins and losses, your account has had over a certain amount of time and money deposited. Your account is then compensated for the losses with smaller, or medium amount, wins that will always see you losing over the long term.

Have You Noticed

Have you ever noticed that you miss out on a good winning combination because just one reel wasn't in the right position? Then lo-and-behold on the very next spin the symbol you needed is right where you needed it to be on the previous spin! Random? Nah! Teaser? Yes!

When in a bonus game and, for example, you have to select 3 symbols from a group of symbols in order to reveal the bonus money, number of free spins, or number of free spins and the winning combination multplier factor, 'beneath' the symbols. Once you have made your choices and the selections are revealed all the other symbols may be revealed as well - often with a better option than the ones you picked. Rest assured that had you picked the 'better options' you would still have made the EXACT SAME choices - So it's no use saying, 'If only I had picked that symbol...' As you don't know what's 'under' any symbol at the start of the bonus pick, the computer can, and does, calculate the amount of free spins etc. it is going to give you, and then reveals whatever it wants to 'under' those symbols you both did and didn't choose. Nothing is actually ever 'under' those symbols to pick from, the machine simply changes the icon picture to whatever its current calculation amount tells it to reward you.

Have you also noticed that after a modest win, or payout, assuming you keep playing the same slot machine, it almost seems as though the game NEEDS to win that payout back before giving you another, abeit smaller payout.

Have you ever been playing the slot machines, at for example $1 a spin, and you get a reasonable size payout win and wish you had bet $5 like you were a few minutes ago? Well rest assured had you been betting $5 a spin the win would not have been 5 times as much as your $1 spin - the machine would not have been 'ready' to payout that amount at that time.

In my experience it seems quite obvious that slot machines have to have some sort of computer coded system at play to ensure you can't win over and over again - Which is why when you do win big it is always followed by a long cold losing streak.

When bonus round occurs it ALWAYS seems the bonus round happens 2 or 3 more times in a short period after the first bonus round, then no bonuses for ages - and lots of cash gone.

Also in my experience, any big wins I've had in the past have come when I've spent a small fortune on that particular slot - almost as if the slot is forced to bring you back in line with the payout figure percentage rules.

Left to right paying slot machines are designed so high paying symbols are frequently on the 1st reel, slightly less frequent on the 2nd reel, less again on the 3rd reel, less yet on the 4th reel, and very rarely on the last reel. It is another trick by slot manufacturer's to gives you the feeling of possibly winning and missing out on the last couple of reels.

The online casino wants to keep you as a player - when playing you may seldom get any wins - then when you are near your last money in the machine you receive a moderate win - just enough to make you come back to that casino for more.

I've played them long enough to believe that they're not random, but as I said, it's my opinion from my personal observations, and you're entitled to yours. Next time you are playing slots stop and wonder why those top slot symbols and/or scatters mysteriously vanish after a while - short-term random, sure - long-term random, not so much...

Feedback on This Article

1 - A Mathematician Agrees

Recently Disabled World received an email from Dave M. stating his opinion. With his permission we have added the content of his email below:

Hi, I have just been reading an article by Jungle Jim on slot machines that was posted on your site, which was very illuminating, and everything he says seems to be quite accurate. Although the article is from a few years ago I found the contents gave quite a representative appraisal on online slot machines and land based slot machines.

My own area of interest however is the online slot machines.

Over the past few months I have been conducting my own research being a mathematician I was interested to find out if these forms of gambling were in actual fact random number generated as the major casino's , bingo halls and other gambling establishments claim them to be.

Firstly I played an online popular slot machine after joining a popular bingo hall and online company. And low and behold after depositing a modest sum had a virtually immediate win followed by subsequent wins giving me a substantial reward on my investment.

Then as if a button had been pressed to say OK this person has won enough and is now 'hooked' when trying other slot games those wins accrued from a previous slot game was starting to be eroded away quite rapidly with a succession of totally win free blank spells apart from very low denomination pay outs.

So before the 'winning pot' had been exhausted I returned back to the original slot game to try again after a day or two. And low and behold it subsequently eroded the rest of the winnings paying absolutely nothing in the way of substantial wins, only small denominations until it was all gone, this in my opinion is a very systematically heavily controlled form of gambling which also in my opinion is not random at all.

I went on for the next several weeks to play and document all the wins and losses from some free game plays to see if there was any difference between them and the paying games and over a period of time playing the free games found that these games always paid substantial wins consistently.

However in between when switching back to the paying money slot games it was always whittling whatever I deposited away, without any substantial wins whatsoever. This I documented and found over a period of time that the wins I initially procured was taken back three fold.

So my research has concluded and justifiably concurred with Jungle Jim's opinions that online slot machines are not random number generators at all and are in my opinion being governed by the operators and companies that are running them.

2 - RNG is NOT RNG

It seems there are many many people out there who agree completely with the article above. Here is one such email, (permission was obtained to include it on this page), from Lewis T. who wrote in under the heading 'RNG is NOT RNG...'

Hi, I'm a fellow slot machine player at a few of my neighboring casinos and way before I came across your post, I noticed those patterns and it wasn't just with slot machines but also with Roulette when I saw the momentum of the ball slow down, rest in one spot, then started vibrating extremely, then rolled around the metal ring and land in another pocket. From that point on I stayed away from roulette and would always watch closely as to how the ball would do the things it would do - yet no one would notice it but me!

As for the slot machines, I would take videos of how the reels would go into hyper-speed all to avoid the bonus symbol it would, and or should, have landed on. All the casino games are suppose to be regulated but who can you really trust them when money runs the world and the gaming commission is getting their pockets loaded by the casinos that are suppose to be operating fair games.

These places have a operations room that allows them to control the winnings and the losings, from the games all the way to the rewards cards they persuade you to sign up for, all for them to regulate you even further.

It has been too many times that I've sat down, inserted my rewards card, inserted my hard earned money and played until I exhausted my $100 in the machine. Then I would sit and watch someone sit right down behind me and play the same game and hit so many bonuses RIGHT AFTER I FINISHED PLAYING! And it wouldn't be just one instance.

The way my mind works I can focus on the whole game verses just focusing on one reel and see the rhythm on wins and loses, and this is just from me!

How are these establishments, the gaming commission, and all the other 'gaming regulators' able to get away with preying on people and get away with it???

3 - Slot Games are Not Random at All

John V. wrote into Disabled World to give his opinion on the unfairness of slot payouts:

The opinions of Jungle Jim to me are what I have been saying all along as well. The games are not random at all, to me the one thing I notice most is 100% of the time you get free spins or a bonus on one game, win some money, then guaranteed after if you keep playing that game you will not get another free spin or bonuses for a long period of time.

What I do is if I get free spins or a bonus I will spin maybe couple times after knowing I will get nothing, then I will change games right away. You have to be very focused when playing and be very patient. When you have low balance bet small as you have to slowly build up your balance, then when you get to around 200 I would say you can start playing the jackpot games, bet more per spin on regular slots etc.

They are definitely not random they try to brainwash you and tell you they are, but when you're an experienced player like myself you play a game for a while give it a chance don't go in thinking I will play till I get free spins or a bonus you could lose a lot of money thinking that. Just play 20 spins or so if theres nothing then move on don't get lazy and stick with the one game, be focused take your time if you feel like your getting very frustrated and angry turn the casino off take break if you don't you will lose it all with in minutes.

It's a game between you and the casino. You can win once in a while, but don't go in expecting to win and wonder why a game paid out so well yesterday and today there is nothing at all. Emotions are key, be relaxed, be alert, and take your time be smart, and you have a good Chance in winning. I have done it 7 times. I have withdrawn money in the last few months that's pretty good so it can be done. Good luck to you all.

Let's Keep the Discussion Going!

So, are slots really random? What do you think? Can you add to the above lists on how you think slot machines may be cheating? If so contact us, as we'd be interested in more opinions.

Are slot machines really random
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  • If you are planning a trip to the gambling capital of the world, Las Vegas, then you'll find some interesting facts in our article - Visiting Las Vegas to Play Slots.

It has been said; Slot players don't lose because they never win, they lose because they don't quit when they're ahead...

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