How Do Online Casino Slots Work

Why are casino slots so popular? After all, when you enter a casino, you’ll see a row after a row of slot machines. In fact, the majority of casinos reserve around 70% of their gaming floor for slot machine games. This is not a mistake on their part — slots are what brings the most income.

The reason for such success and popularity lies in the fact that this game is incredibly simple. There’s no learning curve to it, you don’t need years of experience to become a successful slot player (unlike with poker and other games of skill). To play slots, all you need is the ability to press a button. Game designers decided to make their machines look promising with loud and flashy (even tacky at times) rewards, all with a goal to make these machines more appealing.

The first gaming machine was created in 1887. It was a poker machine which had 50 cards in use and five drums. There was no automatic payout until four years later, when the first proper slot machine came to be. It had three reels (only one row) and five symbols, with the Liberty Bell being the most valuable one.

Before the technology entered the picture, slot machines operated mechanically, with a spring stretching itself when a player would pull the lever down. The spring would bring reels to life and eventually put them to a halt, revealing if you’ve spun a winning round.

But, when you play online casino games, there are no springs on the Internet. So, how do online slot machines work? There are several parameters you ought to know of, starting with what replaces the mechanics of a physical machine.

Virtual Springs

Even before gambling went online, video slots started working electronically. The spring we’ve talked about got replaced by a Random Number Generator, which is in use in online slot games.

Random Number Generator or RNG for short — is a computer mechanism which decides the outcome of a game. It makes sure every outcome is always random and independent of any outside factors. For instance, it doesn’t change its methods if you place the maximum bet. It also doesn’t care about results of previous spins. As a consequence, you as a player have no means of predicting the outcome or influencing it in any way.

Just like New York, the RNG never sleeps. It’s constantly going through a set of numbers (how much numbers depends on how much possible reel combinations there are), even when nobody’s playing. When you press the spin button, it stops on whatever random number it was currently on. This number determines which positions the reels will take up, and once the animation stops, you’ll find out whether you’ve won or not. The reason as to why the RNG works non-stop, instead of just when it’s in use, is to make it impossible for players to figure out a pattern.

Reel Positions

The RNG, as we’ve explained, picks a number which corresponds to a symbol that shows up on the reels. The position in which the reels stop is called, quite creatively, a stop. Video slots usually have from 64 to 256 stops per reel. Obviously, the greater the number of stops — the lower the odds of winning. To win a round of slot, you need symbols to show up in certain positions, as they have to form an active payline.

There’s an exception, though. Scatter symbols don’t need to be adjacent to each other, you just need a particular number of them to show up. Scatters are special symbols which can grant you free spins and trigger bonus game modes. These, in turn, provide you with more winnings (that’s the idea, at least).

Return to Player

Return to Player is a statistic all slots have. This determines how often a machine will pay out. As such, RTPs are the opposite of a house edge, which is a metric that shows how much money goes to the casino. For example, if you come across a game with an RTP of 90%, its house advantage is 10%.

The thing with RTPs is that they are not a guarantee for a win. If the RTP is 95%, you won’t win 95% of your rounds. RTPs are measured on millions and billions of rounds, and as a result, they don’t influence single playing sessions. You can go on a machine, play for several hours and lose every single round. That won’t mean the game doesn’t have a high RTP or that it’s rigged in any way.

Basically, RTP helps us choose which game we should play. But, just like house edge, it doesn’t represent chances of winning — an RTP of 93% doesn’t mean you have 93% chances to win.


Another thing to consider is a machine’s volatility. This signifies how much a game will pay and how often it tends to do it. Low volatility means that the game comes up with winning combinations frequently, but they don’t give out mouth-watering prizes. On the other hand, high volatility will be scarcer in wins, but they will be big. The ideal situation is to find a highly volatile slot with a high RTP.

You should use volatility to determine your betting strategy. If you’re playing with high volatility, you ought to bet lower, as it will allow you to play more rounds and land on a big win.

Online vs Offline

What’s better, playing online or live? The truth is, online’s better. Land-based casinos operate with physical slot machines with the RTP between 85-90 percent. Online slots, on the other hand, come with an RTP usually from 92%-97%. In some rare cases, they’re even higher up.

Furthermore, you have more options when playing online. There’s a larger number of games in offer, and they come with multiple different possibilities. You can play anything from classic three-reel slots to the most common five-reelers. There are even games with six and seven wheels which offer a multitude of paylines, with some of them going over 2000.

Don’t Fall For Theories

In the first half of the 20th century, due to the nature of mechanical slots, there was a possibility to predict the outcome of a slot machine game. As the mechanism wore out in time, the reels could become weighted and you could spot a pattern, allowing many ‘one-armed bandits’ to profit by pulling the lever.

Today, with an RNG at helm, this is no longer doable. As we’ve already mentioned, the RNG is independent of what the player does. On top of that, while RTPs ensure a machine has to pay out, they are measured over an extended period of time.

However, there are people who misinterpret the real meaning of RTP and believe machines pay in waves. When it’s in a winning cycle, it’s a hot slot. A cold slot would be the one which is in its losing phase.

This doesn’t work in reality. Thanks to the RNG, a slot outcome is a random event — just like flipping a coin or rolling dice. If you roll a dice a hundred times and get a hundred fives (which is possible, just improbable), there’s nothing that suggests this trend has to change. With the next roll, odds of another five will be 1 out of 6, just as it was the first time around. The same logic goes for slots.

Over to You

Online casino slots utilize a system called Random Number Generator to determine the outcome of the game, which is always genuinely random. As a result, they are unpredictable, making slots purely a game of chance, where the only thing you can rely on is your luck.

When playing online, do a bit of research beforehand and check out which games offer the best RTP. The higher the RTP, the more chances you have to spin a winning round. Due to the nature of the game, strategies are not a viable option. When you play, play for fun and don’t take it seriously. Good luck!

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