When most people talk about slot machines being rigged, they generally are querying if the machine has been illegally tampered with. This is rarely the case and slot machines go through masses of rigorous testing to make sure they are fair based on the data that’s been submitted with them.

However, technically slot machines are rigged. They are set up in a way that the casino, over a massive period of time/spins, will make money from that machine.

Throughout this article, we want to break down how this works and why they are still the most popular game at any land-based or top online casino.

How Do Online Slots Machines work?

When you look at a slot machine you generally see a game that host several reels, usually ranging from 3 to 5, although online slots have seen them vary even more than this. On each reel is a series of numbers or symbols and to win, the player needs to spin the reels and hope they land in a sequence that will return a payout.

Most slot games look or feel different from each other. This might be to do with the theme, music, payouts, features or functions of how the game works. The reality is that this is all for show and actually, all slot machines work in the same way.

Before we dive in a little deeper, it’s worth noting that slot machines are extremely complex mathematical machines. It’s common for people to talk about when a slot might be due to drop or how likely a certain feature might occur based on previous results, but this is virtually impossible to tell and you’d need millions of spins worth of data to even try to start predicting.

There are two key elements that every slot machine has. This is an RTP (Return to Player) and an RNG (Random Number Generator). Let’s kick things off with the RNG. The RNG is designed to make the slot machine as random as possible. This makes hacking and predicting outcomes almost impossible. However, the games aren’t actually random, instead, they are known as pseudo-random.

Pseudo-random is where a physical event has to take place to get the outcome for that game. A good example of how this works would be a roulette wheel. When the ball travels around the wheel it does so at speed. The wheel spins in a counter-direction to the ball and it would be impossible to know the reaction it would have once it makes contact with the wheel and then lands in its final resting spot.

But it is actually possible to work it out, technically speaking. To do this you would need to know the exact force that the ball has been released at, along with countless other data such as weight of the ball, size of the number slots, the resistance of the wheel etc. Basically, things you’re never going to know or be able to work out without an incredible amount of research.

This makes a roulette wheel as random as it can be. However, it’s not fully “random”. Slots work in much the same way. They are incredibly complex, but they are not uncertain. The RNG goes a huge way to give these games an erratic sequence of numbers, but they aren’t truly random.

How the Random Number Generator Works (RNG)

The goal for the RNG is to create a sequence of numbers that then converts into how the reels on your screen will appear. There are billions of possibilities that are created from a unique algorithm applied to each game. In fact, these algorithms can be changed to create different games types, adjusting features like volatility to make the slot play differently.

The algorithm starts with a seed number. This can be taken from anything but can be as random as the time of day, as an example. Three equations then take place. A multiplication, an addition and a division. The seed number has then been taken, calculated and then spat out to create the first random number. This continues for each reel to create a range. The seed for the next reel is then taken from this range and so on for each reel.

Let’s say, for example, we took the time-of-day quarter past two in the afternoon. The seed number is 1415. Say we randomly multiply this by 5, add 10 and divide by 20. This gives us a number of 354.25. This number would then have some reference to a symbol which then appears on your screen.

As the time-of-day changes for the seed number, along with random number appearing at each point for the equations, it becomes almost impossible to track, unless of course, you’re a computer. We mentioned that the numbers aren’t totally random, and this is true. But it would take billions of spins to get to a point where the sequence would start to repeat itself.

To put this into some context, if you assumed a sequence would take 4 billion spins until it started to repeat itself, this would mean that, on a 90% RTP slot, someone betting 25c per spin, would spend $33 million waiting for the cycle to then start again.

The next spanner in the works is that of the RTP (Return to Player). Each slot comes with an RTP which is represented as a percentage. This has been designed so the casino is guaranteed to make money on that specific game, something important to note if you like playing at real-money slots.

For example, a game that has a 95% RTP means that for every $1 staked, 95c of that money would be returned to the player and 5c would go to the casino. RTP rates differ from game to game but usually hover around the 95% mark for the most part. Anything less than 90% in the modern-day casino is considered very low and likely should be avoided.

It’s worth noting that when you stake $1 on a 95% RTP you aren’t going to lose 5c with each spin. This would make the game pointless. The RTP is designed so that it lets the punter win sometimes but over a massive range of spins, the casino will make a profit. This is called variance, which is sometimes referred to as volatility for slots.

To surmise, slots are basically just computerised algorithms which are slightly in favour of the casino. They allow players to win sometimes and make the casino a slight favourite overall, which makes them exciting to play as a result.

Inside a Mechanical Slot Machine

Before diving into the nitty and gritty, you should understand the difference between virtual and mechanical slots, if the topic is unfamiliar to you. A mechanical slot might seem relatively straightforward, but it’s actually a complex bit of kit to understand how it fully works. They have been around for a lot of years and whilst they have evolved, for the most part, the process is the same.

Mechanical machines are made up of the following components:

• Coin slot
• Lever
• Reels
• Brakes
• Payout trigger
• Winning paylines

All of these components need to come into play at some point before a winnings combination can be created. Just like online play, games are random, and they create their sequences based on pins within the machine adjusting to certain lengths to trigger a payout.

Let’s take a look at the full process.

 Mechanical slots have plenty of moving parts (Credit: Alamy)

Once the coin has been inserted into the machine and the lever has been pulled, a hook mechanism inside the machine pulls the kicker forward in the direction of the player.

Gears inside the machine start to move quite quickly as they latch onto a control cam. Once the spring returns (lever released by the player) the gears start to slow down, which causes a mechanical delay.

In the back of the machine is a cam plate and this cam plate stops the kicker, which in turn allows the discs and the plates to rotate. This happens with each of the reels in the machine and they stop one at a time to create suspense in the game. What the game is doing once the reels stop is feel for the length of the pin on each reel. This then works across each reel before creating a winning or losing combination.

Can Casinos Adjust the Slot Machine Algorithm?

The short answer to this is no, a casino cannot change the algorithm on a slot machine. The only people that can get access to this are the game developers.

However, the algorithms of games can be changes. It’s not uncommon for developers to go back and change how they work, change the seed numbers or change the range of numbers it can land on it to suit any updates in the game.

The problem that they then have with this is that they need to resubmit the game to the appropriate governing body so they can check the game is still true and fair, meeting the numbers that are linked with it.

One of the best things about online slots is that there are so many now that a casino can pick and choose which games they want to promote. The need to change or adjust anything like an algorithm is almost zero given there is likely already an option that fills their brief, should they be looking for a specific type of game to promote.

How to Find the RTP of a Slot Machine

All slot machines have to come with an RTP by law. It also has to be accessible for the players to find this number as it does change how a game would play out.

One of the easiest ways to check the RTP is to open the game file (paytable) for the slot once you load it up. In here you will see info on how the game works, what the symbols are worth, any info on bonus/feature rounds, bonus buy slots option, and any other info you need. The RTP will be highlighted here along with the company who made the slot.

If for whatever reason the RTP is not there, then we would be inclined to contact the casino directly. They should have this sort of information on file or at least be able to access this pretty quickly.

Failing that, you can contact the game developer as they will also have this info. It’s essentially the game developer that sets the RTP anyway, with the casino having no say over how it works. Most of the bigger slot’s developers are pretty easy to get a hold of and this sort of information is easy to obtain.

Progressive Slots

Progressive slots are some of the most popular games in any casino. They allow players to win incredible sums of money for what is a relatively small investment. No games in any online casino payout bigger than progressive jackpot games.

To make the huge sums of money, the games need to work a little differently than your classic slot. They take money from each spin in the game and then pool this money to create the jackpot.

For example, it may be set at 10% of each spin goes into the jackpot. This means that if you were to make a spin of C$10, then C$1 of that spin would go into the jackpot. As more people spin, more money goes into the jackpot and it progressively grows. Hence the name.

It’s also worth noting that with these games, a lot of them are hosted by the game developers and not the casino. This means that if the developer has this game in 10 different casinos, players from each of the 10 casinos would all contribute to the same jackpot. This is the main reason why the biggest jackpots get as big as they do, given they have huge numbers of players across multiple casinos all contributing.

You can generally see when a progressive jackpot was recently won by checking the jackpot total. If it’s low for that game, then it’s likely been recently won. Historical results for most of the progressive games can be found online for reference.

How to Pick the right Slot Machine to Improve Your Winning Chances

It’s not easy to win at slots long term. The odds are literally stacked against you, but then, that’s true of any casino game. You just need a bit of luck.

However, there are always that you improve your chances of winning. The first and probably the easiest is to play games that have a high RTP.

We’ve already spoken about RTP and how that works, but you need to choose games where this number is as high as possible. This means that the casino is taking the least possible amount of money over a huge selection of spins.

It is worth noting that with RTP you need to take into account sample size. If you play 10 spins and lose each one on a 98% RTP slot, then the game is not rigged, you’ve just not hit a sample size that negates any variance in the game. The more you play, the more it will even out.

The next thing we want to note is that of volatility. Each slot comes with a volatility rating, usually of low, medium and high. Volatility is often referred to as variance and this is in relation to the frequency of when slots payout.

A game that has a low volatility rating means that you’re going to get paid smaller amounts, but more often. Games that have higher volatility ratings mean that you’re getting paid less often, but when you hit, you get higher winnings. If you’re wanting to improve chances of winning, then you need to be targeting games that have low volatility rating. Read our full overview on slot volatility to gain a better knowledge on which will suit your playing needs best.

Can You Improve Your Odds of Winning Online Slots?

Your odds of winning on a slot are fixed and about as random as you’re ever going to find. Some will state that you can implement strategies or a classic on fruit machines was the brightness of the lights would signify when games were going to drop, but this is not the case.

The only thing that you can control is how much variance affects your game. The more you play, the lower the variance will be. Technically if you play millions of spins, you’re likely going to be somewhere near the RTP and if you’re lucky, you might be up a little. That's why many players take advantage of free spins bonuses available at top casinos.