The outcome on a slot machine reels is determined by an electronic device operated by a software system. This inherent program decides which combination will show on the reels and therefore, the odds for you to hit a big prize.
Every slot machine has its own set of winning combinations, corresponding with particular sets of symbols aligning on the different pay-lines. Usually only one combination is related to the highest winning possible, the jackpot. If we imagine that there are 10 different symbols on one reel and that the slot machine has three reels, then the odds to hit the same symbol one every reel on an active pay-line is 1 on 1.000 (10^3). With a 5 reels video slot the odds to get a jackpot are even less, 1 on 100.000 (10^5).
The software system that is “responsible” for the virtual odds is called RNG, Random Number Generator. It works generating in a very fast manner casual numbers that correspond to a certain outcome on the reels. The online casino for each type of slot machine predetermines the odds and no other factors can affect the results.
Practically speaking, there can be a difference between the theoretical odds and the actual ones. The RNG has no memory, and the same combination can be presented more times in a row. It’s important to keep this in mind, since many slots players have wrong beliefs when it comes to slot machines. Some of them rely on “due jackpots”, hoping that since a machine has not paid a jackpot for a long period of time, the prize will soon be won. But it is not like that, you can play a slot machine for ages and not hit the jackpot, or theoretically you can just put some coins and win the jackpot twice in a night, extremely rare event but a possible one.
In the past land based casinos used to program the slot machines so that it would have shown the symbols close to getting a jackpot more frequently, giving the players the feeling that they are very close to hitting the jackpot. They did this to keep them playing and playing. Now in jurisdictions that have strict gaming regulations, this kind of slot setting is not allowed anymore.
When looking at a specific slot machine, the slot payout will reflect the virtual odds of a certain combination, the higher the jackpot is up for grabs, the lower the chance is to hitting the right winning combination. The Random Number Generator is responsible for the payout percentage of the machine. That percentage has to be certified by a third party authority to ensure fair gaming. The rules require that a minimum percentage has to be paid back to players. Payout percentage tells you how much money is paid back to players, on the total of coins bet. A 96% payout means that out of 100 credits, 96 go back to gamblers. The remaining 4% is the casino margin.
Now that the competition in the gambling industry has become fierce, payout percentage are going up to 97%, giving players better chance to win amazing prizes.