This is a question which fills thread after thread, and post after post, on various casino discussion forums. The implication is that it fills the thoughts of many (a majority of?) online Casino Players.
Let's give a whirl at answering this question.
As with all things, properly phrasing the question is as important as properly organizing the answer. I think, however, that the question stated in the head of this post has been phrased for us. All that is left to do is to hopefully organize the answer.
In doing this, I'm going to split the discussion into 2 parts. Part 1 will deal with slot games. Part 2 will deal with all of the rest.
Onward to Part 1 - Do Online Casino Slot Games Cheat?
First, what does "cheat" mean? I figure it means that the game does not do what it is supposed to do. For a Slot game there is usually only one definition of what the game is supposed to do - it is called the Slot's Paytable.
A. If a particular combination of symbols appears on a payline on which you have placed a wager, then the win amount for that payline should equal what is defined in the paytable. If the slot does not do this, then it is cheating.
B. If a particular combination of symbols is defined as a winner on the paytable, then it should be possible for that combination to actually occur during game play. (In specific, a 5-reel max pay stop should have that stop on all 5 reels.) If not, the slot is cheating.
Otherwise, what? Well, that's it - end of story. A slot cannot cheat in any other way that the player can be aware of.
BUT ... can the slot cheat in ways that the player is not aware of? Well, I think that's pretty easy to answer - sure it can!
Example #1. The software code that analyzes the results of the reel stops finds that a high-paying combination has occurred. The Casino doesn't really want to pay for that combination, at least this week. So, the code simply re-spins the reels.
Example #2. A Jackpot is won by a customer, but that customer doesn't really exist. The Jackpot is reset to its seed value, and the Casino keeps the Jackpot amount.
Example #3. The software code for the game has as one of its input parameters a "win percent" factor. The game runs, and let’s say that this "win percent" factor is 90%. The first thing the game code does is generate a random number. If that number is less than 90, then the game plays normally. If the number is greater than 90, then the game runs 10 spins and returns whichever one of those ten spins results in the lowest win amount for the player.
Unfortunately, you don't really know whether a particular slot is cheating or not. Hmm. Let me re-phrase that - it is very hard for you as a single player to determine (and much harder to prove) if a particular slot is cheating. One of the reasons is that you need to have played a very large number of rounds (50,000, 100,000), AND you need to have kept some sort of records of that game play.
You sit down and play 500, or 5,000, rounds of the slot, and you lose some money (or maybe a lot of money). Was it just bad luck? That certainly could be. Maybe this slot just doesn't have a very high payout? (A link to a long article describing game payouts, aka Return to Player or RTP.) Or is the fact that the slot is cheating hidden behind what is called "high variance"? (A link to a long article describing this subject.) That's also entirely possible. Or maybe the slot really is high variance?
The bottom line is - you don't really know, and at this point you can't really know, whether the slot is cheating. All you do know is that you lost money.
Now, some slot players think that because they lost money in one session, this means that the slot "owes them". Their next session is sure to be a winner. (aka, The Gambler's Fallacy,)
So, they'll go in and play the same slot again later, and they'll (probably) lose more money. They might do this two, three, five, ten, whatever number of times before they finally (hopefully!) just give up and move on to another slot.
So, is the slot cheating? Or maybe the slot's payout just sucks. Or maybe it is high variance?
What is a poor slot player to do?
***** A Something Better Than Nothing Solution *****
First, look for whether the casino publishes a Random Number Generator (RNG) Certificate.
These are usually found by clicking on a very small graphic at the bottom of some web page, with the graphic displaying the logo for a Certificate company. TST and iTech Labs are probably the most common online casino RNG Certificate sources, but there are a handful of other quality providers that you might come across.
Here are some links to some example RNG Certificates.
There are (at least) three things to be wary of here.
Thing #1. They say they have an RNG Certificate, they show the Certificate Company's logo, but if you click on it then nothing happens.
Thing #2. They have the Certificate Company's logo, or a link somewhere within some document on their site that says they have the RNG Certificate, but when you click on it all you do is go to the Certificate Company's web site.
Thing #3. They have an RNG Certificate, but their name is no where on the document. All they have done is linked to someone else's Certificate.
Second, look for whether the casino publishes a Monthly RTP Report.
These can sometimes be found under web pages titled "Fair Play", or "Certified Fair", or like that. Here are links to some example reports, from three different Certification companies.
Now, there are (at least) four things to be wary of here.
Thing #1. The Casino doesn't have a report, but tells you (maybe on their home page) that their RTP for pick-a-month was 98.17%. Why should you believe them? They might be running games that cheat, but they are going to tell the truth about their RTP?
Thing #2. Affiliate sites will tell you that the RTP for a particular Casino for pick-a-month was 98.17%. Affiliates make money by driving you to the casinos that pay THEM the most for your business, NOT the casinos that pay YOU the most for your business. Something just slightly less than 100% of affiliate sites, super-affiliates like Casinomeister included, will "present innaccurate data" when it comes to reporting a casino's RTP. (Notice how I avoided the use of the word lie. Then notice how I cunningly included it anyway.)
Thing #3. The Casino tells you that they have monthly reports, but you can't find them anywhere. Liberty Slots is one example of this. The page http://www.libertyslots.eu/cfg has a link which launches the following PDF - http://www.libertyslots.eu/images/124.pdf. (Liberty Slots - show me some numbers please.)
Thing #4. The RTP report comes from some place like "RTP Reports R Us". In addition to the three companies above (TST, eCOGRA and CFG), I know of two other reliable RTP Certification sources - iTech Labs, and Price-Waterhouse Coopers (At the time I write this, I think PWC still does this).
Why have I labeled this solution only "Something Better Than Nothing"? If you've launched any of the RTP reports linked above, you'll note that all of the slots are lumped into a single number. Most online Casinos offer 100, or more, slots. There might be 5, 10, or 15 real stinkers in there (stinker in this case being defined as a slot that has an RTP of 85% or less), but their stench is hidden by the crowd.
***** A Something Better Than That Solution *****
Look to see whether the Casino publishes the Theoretical RTP for each slot.
As I write this there are a few companies that do this - Galewind Software, NetEnt, BetSoft. I believe Rival does, but if they do then they've done a superb job of hiding it. IGT says they do, but if someone says that they do Thing A and in actual fact does about 20% of Thing A then that would be IGT. (I also have to say that even though NetEnt and BetSoft do provide these numbers they could not have hidden them better if they tried.)
And then look for all of the "Something Better Than Nothing" stuff.
This will do two things for you. The first is that it will identify the "stinkers" in the barrel. The second is that the Certification company will ensure that the Casino did not report a 95% RTP value for a "stinker" 80% RTP slot. In other words, the Certification company will try to make sure that the Casino isn't just lying.
Now, some might say that an Even Better Than That Solution would be for the Certification company to break down the RTP Report's Slots group into the RTP for each of the slots individually. But there is a pretty big problem there, and it has nothing to do with telling the truth, lying, the Slot, the Casino, or the Certification company. It has to do with the sample size.
I can't know for sure, but I suspect that a large number of those 100 or more slots don't see a lot of games played every month. Statistical analysis of small sample sets usually results in some pretty wild swings. So, Slot A might report an RTP of 67% for month 1, 93% for month 2, 127% for month 3, and like that.
***** A Best That I Know Solution *****
This is from Galewind Software. I've linked it above, but I'll link it here again.
In addition to providing the Theoretical RTP for each of their slots, they also provide the Standard Deviation, the Variance, Line Pay Hit Frequency, Average Number of Spins Between Bonus Game (or Free Game) Wins, and like that.
At the bottom of the page they also include a lot of very interesting information, again for each slot in the collection. One of the interesting bits there is the answer to the question: "If I place a max lines bet, how often can I expect to at least break even on my total bet?"
They also provide their monthly RTP Reports (with dynamic run charts for each report group, which I have to say beats the living hell out of having to load 12 separate freakin' PDF files).
And they make all of this information so easy to find. Basically, all you need to do is click on the Help button from anywhere in the Casino. The resulting list in the popup window will always have 2 line items - Game Returns (RTP Percent) and Certified Fair Gambling. You have to be playing a slot game for the Help list to contain the line item Slot Statistics.
A request of Galewind Software - if you've managed to find this blog, and are reading this, then something that I would like to see on this Slots Statistics page is the percent of total RTP that comes from standard payline wins, the percent from scatter wins (if applicable), the percent from bonus wins (if applicable), the percent from free spin wins (if applicable), and like that.
I saw in a Casinomeister thread that, as I write this, you're working on a new project that will help players understand Standard Deviation and Variance through the use of charts.
I think this would be just great. I hope this projects is completed, as I would greatly enjoy seeing it.
Other than my suggestion above, I can't imagine it getting any better than this.
***** Bottom Line *****
Do Online Casino Slot Games Cheat? Absolutely. No doubt about. 100% guaranteed.
Certainly not all Casinos cheat. But if there are 2,000 online casinos running in the world, I figure it's a safe bet (no pun intended) that at least 20% of them are cheating at slots.
However, if you follow the guidance in the "Something Better Than Nothing Solution" (while paying close attention to all of the things to be wary of), or the guidance in the "Something Better Than That Solution", you're reasonably safe.
As I mentioned above, Affiliates make money by driving you to the casinos that pay THEM the most for your business, NOT the casinos that pay YOU the most for your business. You can safely ignore any RTP values presented on ANY Affiliate web site. If you follow a link from an Affiliate to a Casino, once again just follow the guidance in the "Something Better Than Nothing Solution" or the "Something Better Than That Solution" and you're reasonably safe. Just make sure to ignore pretty much anything said by the Affiliate.