Online slots are one of the most purely pleasurable parts of any online casino, and that’s why they’re amongst the most popular. Part of the reason for that popularity is that they’re so simple and easy to pick up. You press the button, you watch the reels spin or cascade and, if the symbols line up in the right combinations, you win something.  Of course, modern online slots offer much more than the tradition 3-reel slots in terms of game play, so that, as well as just watching the reels do their thing you also get to ponder bonus rounds, expanding wilds and scatter symbols. Even with these extra factors, however, it doesn’t take long to figure out exactly what’s going on and, unlike poker or blackjack, there are few complex strategies and tactics to consider.

One thing can get in the way of simply enjoying playing online slots, however, and that’s if you start wondering whether the slots, you’re playing are completely fair or not. It’s the kind of thought that usually occurs to you after you’ve had a bit of a losing streak, burned through your stake and are wondering whether to spin the reels a few more times. On the one hand, you know that online casinos are money making businesses and that taking your stake is how to keep their income ticking over. On the other, if an online casino was too greedy and took too much of the money every player wagered then word would pretty soon get around. This is particularly true in the interconnected broadband age, when the details of any online casino that got too greedy and stopped paying out enough to make it worth the players while visiting would be all over the internet before you could say “But I’m feeling lucky tonight.”

Despite knowing that online casinos are major multi-national companies with a reputation to protect it can still sometimes be difficult to stop the doubts creeping in. That’s why it’s comforting to know that there are, in fact, checks, balances and systems in place to make sure that players aren’t ripped off by unscrupulous casinos and that, as long as you play with the right online casinos, you can pretty much guarantee that the slots you’re playing are fair. The question is – how?

Random Number Generator

In the early days of mechanical slot machines, it was extremely difficult for the casinos to make sure that the pay-outs were genuinely random in nature. The mechanical nature of the systems meant that it was often possible for players to figure out, up to a point, when a machine was ‘due’ to pay out. This was particularly the case when casinos took to attaching timers to their slot machines to determine when they would pay out. It didn’t take long for seasoned players to figure out the pattern and take advantage. One of the more famous was a gambler named Cat Hulbert, who took time off from being one of the worlds greatest a professional poker and blackjack player when she spotted a chance to take advantage of these regular pay-outs.  She did this by employing a team of women over the age of 70 to stand playing the slots when she knew they were getting close to pay-out time.

Clearly, casinos were desperate to come up with a better system and they did so in 1984 when a Norwegian mathematician by the name of Inge Telnaes came up with the idea of having a random number generator (RNG) rather than spinning reels determine where the symbols of a slots ended up landing.  The patent for the RNG was purchased by games developers IGT in 1989, and soon taken up by every other slot developer. Using complex algorithms it was able to guarantee that the combinations thrown up by the reels of a slot machine were as close to being genuinely random as is possible (for reasons which are far too complex to go into here it’s pretty much impossible for software to produce completely random numbers, but RNG is good enough to guarantee fairness).

Return to Player (RTP)

Now that you know that the random nature of the reels of a slot is guaranteed by technology, we can look at the return to player (RTP). The RTP is a figure which represents the chances of winning on a particular slot machine. It’s usually given as a percentage, and somewhere on any online casino you’ll be able to find the RTP of every slot you want to play. If a slot has an RTP of 97% then this means that, for every £100 used on the slot, £97 should go back to the player. The higher the RTP is, the less money you’re likely to lose if you play it over a prolonged period of time. That’s not the same as being more likely to win, of course, because that’s something which is also determined by the ‘variance’ of a game.


Variance refers to the type of pay-out a machine delivers. If it has a high variance it will pay out larger sums, but less frequently, while a machine with a lower variance will pay put more often, but the sums paid out will be lower. Even bearing variance in mind it’s a pretty useful rule of thumb not to play slots with an RTP of less than 90% and aim for those offering 95% and higher.


Up to this point you may be thinking that you have to take an online casinos word for it when they tell you about the RTP, RNG and variance of their slots. This isn’t the case, however. In order to be granted a licence to operate, an online casino will have to have all of their systems, including those detailed above which guarantee fairness, tested and passed by independent regulators. Licences given out by the UK Gambling Commission are some of the most stringent in the world, and online casinos are only allowed to operate in the UK if they have been granted a UK licence.

The good news is that all of this information is freely available on reputable online casino sites. Before playing a slot, you can check its RTP and variance (also referred to as ‘volatility’) and the licence which the casino holds will be clearly displayed, along with the licence number, usually at the bottom of the home page. As long as all of this is in place then you can be pretty certain that you’re not visiting a rogue casino and  you can play the slots safe in the knowledge that you’re being treated completely fairly.