Online Slot Games: Do You Understand the RNG?

One of the most misunderstood things about casinos is how slot machines arrive at each spin.

Before the late 20th century, the answer was based on gravity and mathematical probabilities. The handle on a three-reel slot machine would wind a spring. When the spring released, it would send the reels spinning. Another mechanism would stop the reels after a predetermined period, and that was that.

In those days, it was possible for players to count all the symbols of a slot machine and use the laws of probabilities to predict when a big award was likely—and then wager accordingly.

That all changed with Inge Telnaes’ 1984 patent of what later became known as the “virtual reel” system of determining slot machine results, using a random number generator program (RNG).

The physical reels were now just display vehicles for the reel (real) results, which were determined by the computer cycling through hundreds or even thousands of numbers, and freezing the combination of numbers that happened to appear when the spin button was hit.

This is still how slot machine results are determined, in online slot games as well as casino slot machines. will match your first deposit dollar-for-dollar up to $1,000. For a limited time, with an additional $30 deposit, get 200 Free Spins on the brand-new slot, 88 Fortunes Megaways.

It all starts when a slot game is created by the programming engineer. Numbers are assigned to each possible result on the reels, and then duplicate numbers are assigned to the same symbols. High-paying symbols get only a few or one number; lower-paying symbols and blanks get many more. This is how programmers are able to manipulate the payback percentage, also known as return to player (or RTP) of a given slot game.

The random number generator is a simple software program that cycles through numbers at a high rate of speed. Once a slot game goes live on an iGaming site, the RNG begins cycling through all those numbers the slot programmer created in the slot game’s program. It cycles constantly, going through all the possible results in a game, until the spin button is hit to initiate a new game. At that microsecond, the computer freezes the numbers generated by the RNG, and translates them into the reel result you see on your screen. 

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Myths, Misunderstandings & Dumb Luck

These are the facts on how slot games pick results. Before iGaming, many, many players did not accept that the results of their wagers were based on the dumb luck of random numbers. Whole books offered schemes on how to predict when a slot machine was going to hit. But most were complete nonsense, because they were usually based on how slots picked their results before the virtual reel system was developed, when the number of symbols on the reels could still be entered into a mathematical equation.

The reels on a physical slot machine, and the video reels on an online slot, are only there to demonstrate the result reached when the computer freezes those RNG numbers.

Still, the myths stubbornly remained about how slots pick results, and that didn’t change when online gaming began. Just a few months ago, one of those “How to Win at Slot Machines” theories was posted on an internet blog. The method to be used to win was to figure out the cycle of a slot’s spins, since all slot programs use a “seed number” as a starting point. The article suggested that, through consistent play on a single slot game, a player can learn the cycle and know when a big payout was likely to come.

Umm, no.

The reason this doesn’t work is the speed of the computer, and the advancement of modern RNG programs. First of all, unless you programmed the slot game personally, there is no way for you, as a player, to figure out the seed number—in other words, there’s no way to know where in the number set the RNG begins cycling through all possible results.

Even if you did know where the cycle began, it’s impossible to keep track of that cycle. There are literally thousands of numbers—or more—and modern RNG programs are cycling through them at speeds of up to 1,000 number combinations per second. If you stop to take a drink or look away from your phone for a second, you’re probably a cycle or two down the road.

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So Random

This is why the odds of hitting a top jackpot, particularly on a progressive game, are astronomical.

As in 50-million-to-1 astronomical.

And that’s a conservative estimate where million-dollar-plus jackpots are concerned.

Look at it this way. If reel results were something that could be determined through careful observation by the lay person, millions of players would be making tons of money playing online slots, and more importantly, online slots would go away, because operators wouldn’t be able to make any money on them.

Each combination forming a winning result on any slot game is subject to these rules. People win because occasionally, the timing of when a player initiates a spin are just right, and the magic numbers at the instant the spin is initiated fall in just the right pattern to give the player that win.

The virtual-reel RNG method of determining reel results applies to all slots of all types, even where skill elements are added. The RNG even applies to video poker; the numbers are simply confined to the 52 cards in a deck. The RNG in video poker creates the effect of a live game of draw poker in which the deck is furiously shuffled after each hand.

The operation of the RNG means that online slots satisfy the legal definition of randomness. In other words, the results are not predictable.

So sit back, have fun, and don’t worry about how the game is determining the results of your wagers. It’s all timing.

And luck.

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