Are Online Slots Rigged?

FACT: When gambling in casinos far more players lose than win. Yes, everyone who plays is hoping to hit a nice win and cashout with some extra walking-around money. No-one would gamble if they were not hoping to win. Winning is the incentive to gamble. But the reality is that whether online or offline, any gambling operator is a business. They ply you with free drinks or bonuses, buffets or comp points, but they could not offer players these things if someone was not paying for them. As the saying goes ‘someone has to pay for all those lights’ and it should come as no surprise that it is not the casino.

This means that far more players walk away from their gambling experience disappointed than elated. It is completely understandable then that after losing many players end up questioning whether the games that they were playing were fair. To answer this question we put together an extensive article on the subject ‘Are Online Casinos Rigged’. This article explores the safeguards that are in place generally to ensure that the games offered by online casinos can reasonably be called ‘fair’. However, slots games are unique in the way that they work as opposed to other casino games and are worth an exploration in their own rights.

What is fair?

Fair has a different meaning when we engage in gambling than it does elsewhere in life. Ordinarily to be “fair” means that all involved parties are treated equitably.

treating someone in a way that is right or reasonable, or treating a group of people equally

So a fair game would be a game where all participants are equal – i.e. everyone has the same chance of winning.

However, when we are gambling fair takes on a different meaning entirely. It is common knowledge that the games are not “fair”, they are weighted in favour of the house. This means that in the long run the house is expected to win. So these games do not meet the ordinary standards to be considered fair.

What do we mean when we describe a casino game as fair?

Generally when a casino game is described as fair it does not mean that both parties have an equal chance of winning. There are some rare exceptions, but as a rule, it is very unlikely you have played a game where you had the same chance of winning as the casino. So what does fair mean in the gambling context?

The generally accepted meaning is that the game behaves in a manner which the player would naturally expect it to behave. This means that if a game uses a deck of cards, each of the cards should have an equal chance of being drawn. If a game uses 6-sided dice, the die must each have an equal chance on landing on each of the 6 numbers. If it is a Roulette game, each of the 37/38 numbers must have an equal chance of coming up.

You can see this requirement built into the technical standards of some of the more commonly used licenses below:


RTS 7C. a

Where a virtual event simulates a physical device, the theoretical game probabilities should match the probabilities of the real device (for example, the probability of a coin landing heads must be 0.5 every time the coin is tossed).

Gibraltar Gambling Commission

(5) A licence holder should not implement game designs or features that may reasonably be expected to mislead the customer about the likelihood of particular results occurring. This includes, but is not limited to the following:

(a) Where a game simulates a physical device the theoretical probabilities and visual representation of the device should correspond to the features and actions of the physical device (e.g. roulette wheel).

(b) Where multiple physical devices are simulated the probabilities of each outcome should be independent of the other simulated devices (e.g. dice games).

(c) Where the game simulates physical devices that have no memory of previous events, the behaviour of the simulations should reflect the behaviour of the physical devices (e.g. roulette wheel, cards, dice games).

While the above gives us a good idea of what is accepted as “fair” in terms of the function of many casino games, where slots games are concerned these standards would not seem to apply. Why? Unlike other online casino games, which are all simulations of a real-world device where the probabilities of different outcomes are reasonably intuitive to the average person, slot games all function with a hidden mechanic that in most cases prevents anyone other than the developer from knowing what the probability of any event is. There is no ‘real-world’ equivalent to compare slots games to in order to establish whether they are misleading players or not.

The Slots Conundrum

Because slots games are not simulating real-world devices, game developers have far greater freedoms in what they can do. This can be a good thing for players – recent years have seen an influx of imaginative and creative slots games, with original bonus features that make for a far more engaging experience. However, it also means that slots games fall outside of the classic criteria that are required to call a game “fair”.

We need a new set of standards to understand what “fair” means when discussing slots games.

Standards of fairness for slots games

First and foremost, the most basic standard that must exist before any slot game can be considered fair is a definition of the cost that the game should charge the player. As slot games cannot be compared to a real-world counterpart, and therefore there is no equivalent real-world house edge that would be implied by the nature of the game, a slot game must include information detailing the specific house edge that the game is intended to conform to (or more likely, the Return to Player information). Without this information, there can be no reasonable assertion of the fair function of a game.

Return to Player vs House Edge

The Return to Player (RTP) figures provided by most well-licensed slot developers are an industry-standard figure. This figure tells you how much will – on average - be returned to the player from every 100 credits wagered.

So, if a game has an RTP of 95%, for every 100 credits wagered players will receive 95 credits back in the form of winnings and the house will retain 5 credits.

House Edge is the reverse of this figure. It tells you how much it costs you to wager 100 credits. To work out the House edge simply subtract the RTP from 100. To use the example above, the House Edge would be 100 – 95 = 5%.

In our opinion, by choosing to present RTP figures rather than House Edge figures, the industry has played a psychological trick on players. Much like pricing items at a cent below a round number has been shown to make shoppers more inclined to buy due to the feeling that the price is lower, by displaying the higher figure RTP rather than the actual cost (House Edge), it is our opinion that the industry has created a situation where the player has a weaker context to comprehend what the games they are playing are actually costing them. The difference between an RTP figure of 94% and 97% does not at first look appear that significant. But when expressed as House Edge – 6% and 3% - it is quickly apparent that the first game is twice as expensive as the second!

It is likely too late to change this practice now as the industry has educated consumers to look for RTP figures.

Why is RTP so important?

So why is it so important to have an RTP figure in order to have a fair game? In the first instance, cost. If you went into a shop and saw a bottle of wine on the shelf with no price and when you ask a shop assistant how much it cost, they refused to tell you, would you be comfortable buying the bottle of wine? If they are refusing to give you a price how do you know if you have enough money? It is entirely the same with RTP figures. If the game does not give this information they are refusing to tell you how much you a being charged for your entertainment!

That is more of an advertising standards issue than a true game fairness issue.

In terms of game fairness, without an RTP figure, there is no standard that the game has to conform to in order to be considered to be functioning correctly. Part of what allows us to agree to terms of ‘fairness’ within a gambling contract is consistency in expectation of results. When you are playing roulette, you know that each of the numbers has the same chance of coming up. You also know that the odds do not change from spin to spin. It is the same with Baccarat, Craps, Video Poker or Blackjack (with the caveat that for Blackjack, Baccarat and Craps, the odds may change as the game progresses, but with each shuffle/new shooter they revert to a known point). There are fixed odds of any specific payout occurring and these are consistent regardless of when you play. Without an RTP figure the same cannot be assured of slot games.

With a published RTP figure that the game has to adhere to, it would be very challenging to alter the frequencies of the payouts of a slot game while conforming to the published RTP. Where this was attempted it would only change the variance of the game, without impacting the cost to players (as any reduction in size or frequency of one payout would have to be balanced by increasing another payout to balance the change).

Without a published RTP figure, it would be entirely possible for the frequency of payouts to be altered from day to day, session to session or even between one spin and the next. The chances of you receiving any particular win could be changed at will by the operator at any time and there would be no possibility of challenging the operator about this action as there was no agreed-upon ‘price’ that the player was being charged for playing.

Without a published RTP figure, there is no such thing as a ‘fair’ slots game. Full stop.

Regulatory Requirements

Sadly, to date, only a single regulatory authority that we are aware of has mandated that RTP information for every game has to be provided to players – the UKGC:


For each virtual event, game (including bingo), or lottery, information that may reasonably be expected to enable the customer to make an informed decision about his or her chances of winning must be easily available before the customer commits to gamble.

Information must include:

i. a description of the way the game works and the way in which winners are determined and prizes allocated

ii. house edge (or margin)

iii. the return to player (RTP) percentage or

iv. the probability (likelihood) of winning events occurring.

The Gibraltar Gambling Commission has come close to making a similar commitment with the following license requirement:

7.1 Game fairness

(3) Games should be implemented and operate fairly and strictly in accordance with the published rules and prevailing RTP where applicable.

However, while the above does require the games to conform to an RTP configuration, it does not go as far as requiring the RTP information to be published or made available to players! Many of the slot developers who offer games under the Gibraltian license are also subject to UKGC licenses. Consequently, most of these developers are already publishing their RTP figures. That being the case, by grace of the UKGC license the GGC license offers a similar degree of protection to the UKGC license by requiring games to adhere to these published figures.

Until other regulatory bodies insist on the publication of this information, there is no genuine way to hold any software provider or operator accountable for the function of their slots games.

Beware of variable RTPs!

While most well-regulated slot developers do now include RTP figures in their game information, there are a number of developers that offer operators a range of possible RTP settings for their games – to our knowledge the most notable are IGT and Play n Go. This means that the operator can choose an RTP setting that suits their business model (normally low, mid or high). It also means that the same game may be different at different operator sites. It also means that the same game could be altered to function differently between playing sessions. For this reason, it is important to check the RTP information at the start of each playing session, to ensure that the game has not been changed since the last time you played.

Other Standards that are required for a fair slots game

The other significant standard that is placed on well-licensed slots developers is that the games they release may not be “adaptive” in nature. This means that the game cannot change the likelihood of a specific outcome depending on the bet you place. So, for instance, the developer could not make a game that was more likely to result in a red card being drawn if you bet on black or vice versa.

The UKGC’s requirements in this respect are as follows:

RTS 7A. d

Restricting adaptive behaviour prohibits automatic or manual interventions that change the probabilities of game outcomes occurring during play.

Likewise, the Gibraltar Gambling Commission includes the following restrictions:

7.3. Compensated or adaptive games (1) Games should not be “adaptive” or “compensated”, that is, the probability of any particular outcome occurring should be the same every time the game is played, except as provided for in the (fair) rules of the game.

While the definition of “fair” has to be adjusted for slot games to account for the lack of real-world counterparts to slots games, with appropriate regulation standards can be achieved that will ensure that slots games are reasonably understood by players to function in a fashion that all parties can agree on as fair. However, many regulatory jurisdictions will require work on their licensing requirements to meet this obligation.

Regulatory Enforcement - Keeping Slot Games Fair

Based on the above, we now know what standards have been – or should be – put in place to protect players and prevent deceptive games being distributed, but there’s a big difference between simply publishing standards and actually enforcing them. How do regulators ensure that slot developers are adhering to the rules?

The answer to this question has two parts – Random Number Generators and Game Sampling - both of which require the involvement of Testing Labs.

Testing Labs

Testing Labs are independent third parties that are engaged to apply mathematical testing to demonstrate that the games offered at online casinos function in a manner that the regulator has defined as “fair”.

Testing Labs look to check that gambling games are offering results that are both random and in line with the rules as detailed for the game. They do this by sampling the data set of game results and testing the Random Number Generators (RNG).

While Testing Lab certificates are a strong indication of a fair game, there are limitations to the effectiveness of this strategy that we will discuss below.

Random Number Generators

A Random Number Generation (RNG) is, as the name suggests, a piece of computer code intended to create random results. With physical gambling games – like Blackjack or Roulette – the device creates the randomness. The shuffled cards or the spinning wheel serve to create the unpredictable results. When dealing with a digitally simulated game, the randomness has to be introduced digitally – hence the need for a random number generator.

The UKGC Remote Technical Standard impose the following strictures on all RNGs used in games licensed by the regulator:

“Random number generation and game results must be ‘acceptably random’. Acceptably random here means that it is possible to demonstrate to a high degree of confidence that the output of the RNG, game, lottery and virtual event outcomes are random through, for example, statistical analysis using generally accepted tests and methods of analysis. Adaptive behaviour (ie a compensated game) is not permitted.

Where lotteries use the outcome of other events external to the lottery, to determine the result of the lottery the outcome must be unpredictable and externally verifiable.

RTS implementation guidance 7A

a. RNGs should be capable of demonstrating the following qualities:

i. the output from the RNG is uniformly distributed over the entire output range and game, lottery, or virtual event outcomes are distributed in accordance with the expected or theoretical probabilities

ii. the output of the RNG, game, lottery, and virtual event outcomes should be unpredictable, for example, for a software RNG it should be computationally infeasible to predict what the next number will be without complete knowledge of the algorithm and seed value

iii. random number generation does not reproduce the same output stream (cycle), and that two instances of a RNG do not produce the same stream as each other (synchronise)

iv. any forms of seeding and re-seeding used do not introduce predictability

v. any scaling applied to the output of the random number generator maintains the qualities as detailed

Likewise the Gibraltar Gambling Commission includes the following in its Remote Technical and Operating Standards:

11.1 RNG and Game Randomness

(2) The output obtained through the use of the RNG in games shall be proven to:

(a) Be statistically independent.

(b) Be uniformly distributed over their range

(c) Pass various recognised statistical tests intended to demonstrate a) and b) above and the absence of patterns.

(d) Be unpredictable without knowledge of the algorithm, its implementation, and the current seed value (all of which should be secure).

(e) be random and distributed in accordance with the rules and expected probabilities of the game.

These standards are there to ensure that online gambling games, like slot games, produce genuinely random results.

To ensure that the RNGs that are used to power a software developer’s games are functioning to the standards defined above, Testing Labs will subject the RNG to a variety of tests intended to demonstrate that the results being returned are genuinely random and non-predictable. Where this is shown to be the case they will offer certification to certify that the RNG performs correctly.

Fair RNG + Unfair Game = Rig

The sole purpose of an RNG is to produce a random number from a predefined set of numbers. They do not generate the game itself. An RNG is similar to the engine in your car. It facilitates the car moving, but without the car the engine does nothing.

When an RNG is functioning correctly the probability of any number from the set occurring should be exactly the same as any other number occurring. Beyond creating the random number, RNGs do not do anything. And this can be abused.

Let us use the example of a game intended to return the same results as coin flip. As with any fair coin, both heads and tails should have an equal chance of coming up. This game uses a perfect RNG with an output range of between 1 and 50 (so every number between 1 and 50 has an equal chance of occurring). A fair game designer could use the results as follows:

1- 25HEADS
26 - 50Tails

As can be seen above, half of the results from the RNG result in Heads and the other half result in Tails. As long as the RNG functions fairly and all numbers have an equal chance of being selected, the game functions fairly and the coin works as it should.

However, if the game designer instead chose to use the RNG results as follows:

1 - 40HEADS
41 - 50TAILS

The game no longer accurately represents a fair coin. The result will be heads 4 out of every 5 flips.

So despite the fact that the RNG is entirely fair and would pass the tests required of it, by misusing the results of the RNG the game can still be unfair.

What the above shows is that an RNG can function entirely fairly and be certified appropriately by approved Testing Labs, but a dishonest game developer can still take the results of a fair RNG and use them in an unfair fashion. This is not to suggest that RNG certification is not a worthwhile endeavor. Without a properly functioning RNG it is impossible to have any fair online gambling game. As such RNG testing is essential to ensuring that gambling online is fair. We are however saying that RNG certification by itself is only part of the solution and by itself does not demonstrate that a game operates fairly.

Game Sampling

Alongside RNG testing and certification, the other significant safeguard that has to be in place to minimise the risks of unfair games being distributed is game sampling. This is approached in two different ways:

i) Large scale simulation – This is generally required to establish what the RTP of a game is. The Testing Lab generates a data sample of millions of rounds of play. They then divide the total amount paid out in winnings by the total amount wagered and multiple by 100 to get the RTP percentage. We discuss calculating RTPs in greater detail in our article Online Slot RTPs Explained. This type of testing should be engaged by the software developer before the game is released and at any junctures where there are changes to the game.

ii) Game sampling – This process involves the testing lab taking the real results of a casinos games, checking that they are returning within mathematically expected ranges and compiling RTP certification and usually happens on a monthly basis. This process does not tend to look at individual games but rather provides average results for game ‘types’. This type of testing is engaged by some operators.

The problem with Game Sampling is that it is a LOT of work. It is time-consuming and takes a lot of computer resources. Given that – at a rough estimate – there are around 6k slots games online today (probably a lot more), all of which required initial testing for the software provider, and thousands of online operators who could require ongoing testing to ensure that the games are continuing to function correctly, there is more work on this front than we could ever conceivably have the resources to manage.

These two methods do leave gaps. If a software developer were of a mind to, they could change the game after testing and likely no-one would be any the wiser.

So Online Slots do Cheat?

If you have reached this conclusion, you have gone further than we intended. Yes, it is possible that a nefarious developer could change a game after it has been tested. Testing certificates are not an absolute guarantee that there are no cheating games. But there are other factors that have to be taken into consideration before we jump to hasty conclusions. Namely, what are the risks that a license holder would be exposed to by distributing a cheating game and how do these balance against the potential rewards?

Who Controls the Games?

It is commonplace for this service to see players submitting complaints asserting that an operator has manipulated the game/s they were playing to in some manner reduce the winnings the player feels they should have received. Whether they think the game generally is set to never payout (‘I played XXX spins and never received a bonus feature…..’), or they put out a big bet and there was a delay in concluding the round (connection issue), these players conclude that the operator has directly and maliciously intervened to stop them winning. These conclusions are based on a misunderstanding regarding what the operator can actually do.

Gambling operators have very restricted access to the games they offer. They lease their games from software developers. It would be extremely risky for any software developer to allow their clients' sufficient access to change how a game functions. Why? Because if a game is caught cheating, it is not just the gambling operator that risks losing their license. The software provider has to hold a license as well and could be held accountable for the malicious actions of their clients.

Software providers lease their games to a host of different clients. If they were to allow these clients to manipulate the games in a way that was unfair, sooner or later some greedy casino is going to get caught. When that happens the software developer will come under increased regulatory scrutiny and face the very real possibility that they could lose their own license. That means losing not just the cheating operator who got caught, but every licensed operator. The potential risk in allowing gambling operators to manipulate games in any way is so significant and potentially business crippling that the idea that any reputable software developer would even consider doing this is at best described as “outlandish”.

Given this dynamic, it is extremely unlikely that any software provider would ever consider letting any client have any meaningful access to the function of their games. As such, unless the game you are playing has been developed by the casino operator – usually called a ‘proprietary’ game – the likelihood that the casino operator could interfere with the game in any way is vanishingly small.

Loose Lips Sink Ships - How Disgruntled Employees Keep the Gambling Industry Honest

Even acknowledging the significant risks to their business that a software provider would take in allowing their clients to manipulate their games, some players do still believe that the games are cheating them. So let us consider the potential for a software developer to allow an operator to manipulate their games from another angle.

If a software provider were to give a gambling operator enough access to their games to allow the operator to alter the results of the game, how many people would have to know about this?

To begin with, the programmers working for the software developer would need to be aware of this as they would need to build the functionality into the games. The account managers at the software provider would also have to know, as they would have to interact with the clients, choosing which clients were informed of this functionality and training operators on how to use it. Management would certainly have to be aware. On the operator side, how many people would have to know? How many operators would the software provider have to allow to do this to make it worth their while to take such a big risk? So multiple the number of operators by the number of employees at each operator who need to know. Realistically, for a software provider to allow gambling operators to influence their games, scores if not hundreds of people would have to be ‘in the loop’.

The reality here is that it would only take one disgruntled employee to compile some evidence and then release it and huge companies would lose their licenses and many involved parties could end up facing jail time. And given the large number of people that would need to be in the loop, someone eventually doing this would be inevitable.

So Online Slot Games Don’t Cheat?

That is not what this article is saying either. We are not talking in absolutes.

There are a host of reasons that if a software provider holds a license with a reputable regulator, that is it very unlikely that you have played a rigged slot game. However, there are other factors to consider.

Firstly, as detailed at the start of this article, the definition of what “cheating” is with slots games is far more woolly than for any game that is based on a real-world device. If no RTP settings are published for the game then the developer could either change from day to day the settings of the game (simply having ensured that each RTP setting had been tested by a Testing Lab in advance) or allow individual operators to select the RTP settings and this would not be considered cheating. It would not be possible in any other type of game, but the unique structure of slots games would make this practice technically compatible with all licenses we are aware of.

Even setting this aside, the entire system of regulation, testing certification and independent software developers only functions to prevent cheating casinos where there is a robust regulator acting to oversee the market. The incentive that prevents cheating casinos/software providers is that they could lose access to markets, face crippling reputational damage and potentially face prosecution if caught. Where no regulator exists or only a weak regulator licenses the casino/software provider, there is no barrier what-so-ever to the software providers or operators cheating.

The Importance of Independence

The protections that the system we have discussed in this article offers only exist where there is genuine independence between the parties involved. If a software provider is also running its own online casinos and is also operating its own Testing Lab, it is very easy to see how these organisations could effectively work together in a manner that would facilitate cheating.

In 2015 connections between Rival the software company and the Testing Lab that Rival had historically engaged – – were brought to light by this site. Rival and CertainKey shared a Google Analytics code. Google Analytics codes are used by the owner of a website to track traffic activity, behaviour and sources. There is no good reason that we could see – nor that Rival were willing to provide – that two independent companies would share a Google Analytics code. Add to this that at the time there were indications that Rival were in fact running a number of the casino operations that used their software and you have exactly the dangerous scenario we discuss above.

Safety with Regulators

So the key here is to stick with well-recognized regulators that carry clearly published licensing standards and who will insist on a separation between the parties involved in the production, testing and distribution of games. The regulators that we feel reasonably fall into this category are as follows:

United Kingdom Gambling Commission

Malta Gambling Authority

Alderney Gambling Control Commission

Isle of Man Gambling Supervision Commission

Gibraltar Gambling Commission


This list is not exhaustive. There are other local licensing systems (national licenses that solely apply to the function of the gambling operator within your country) that are likely credible as well. However, we would strongly discourage players from putting any faith or confidence in other international type licenses originating in small island states not listed above. Sadly questionable licensing bodies are some of the most prevalent “licenses” in the market.

Danger! Danger!! Fake Games!!!

I have tried to present a balanced discussion of a topic that makes many players anxious above. I have looked to show the weaknesses in the current regulatory systems while at the same time highlighting the various protections that are built into the system and the disincentives to foul play that occur naturally in this type of system. However, all of the protections inherent in this system depend on knowing who you are playing with.

Sadly, in the last few years, there has been a rapidly growing trend of entirely unlicensed operators popping-up and distributing fake versions of slot game titles from other popular providers.

These fake games look identical to games distributed by Net Entertainment, Playtech and Novomatic (and potentially many others) however careful examination of the games and in some cases direct confirmation from the software providers have demonstrated these to be fakes distributed by illegal developers.

These games are especially dangerous. They are dressed up to look like games from software providers that you know and can be reasonably concluded to be trustworthy. However, just because they look the same does not mean the manner in which these games function is anywhere even reasonably close to the genuine article. It would be entirely possible – and in our opinion highly likely – that the top payouts of these fake games have been disabled entirely.

As there are no regulators to require testing certificates, there are no testing certificates. There is no risk of losing licenses, access to markets or clients. The casinos providing these games know they are fakes. There is nothing to stop the groups distributing these games creating them specifically to cheat players. And why wouldn’t they? They are working with unlicensed operators who no doubt would love the additional means to increase their profit and reduce their risk of having big winners.

If you have played at a casino offering fake games you fall into a category of players that we would consider to be likely to have been cheated while playing online.

There is an easy way to protect yourself from exposure to these fake games and that is to stick to playing with operators licensed by the regulators mentioned above.