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How do slot machine algorithms work?

How do slot machine algorithms work?


In the “good old days”, a slot machine was a simple operation: each of the reels was powered by a drum, which had all of the symbols displayed upon it. These would spin after the player pulled the lever, and then stop when the time was right.

However, new technology has created the possibility of online slots, and these super-fun games are a really enjoyable way to spend your time. However, keeping the game random and unpredictable is another matter altogether.

That’s where the Random Number Generator (RNG) comes in. This is a rather clever bit of kit that ensures that each and every spin of the reels is fair. There are no “hot” games and no “dead” reels in online slots, and that’s thanks to this fantastic algorithm that keeps the game working like a charm.

Online slots feature bright lights and flashing images, and many of the modern generation of slots boast video and audio content to keep players on the edge of their seat.

Beneath the razzmatazz, it’s the RNG that keeps the game in full working order. 

What is a Random Number Generator?

The RNG is a piece of software that acts as the slot’s algorithm. It is this that decides which symbols appear on your reels on any given spin, and thanks to the smart coding, you can rest assured that this process is wholly random.

The sequence of symbols cannot be predicted (i.e. there is no pattern), and so a wild symbol could appear in three spins in a row or it might not appear in a single session. That, metaphorically and literally speaking, is the gamble.

Each possible outcome in your game is given a numerical value, and for each spin, the RNG plucks one of these numbers out of the air at random – that could be zero or 1,206,478 – it really is that random!

How does the RNG work in reality?

When you click the spin button on your favourite slot games, the RNG kicks into life and assigns your spin a random value.

This is then fed to the reels, which stop at the assigned combination. It could be a winning spin or a losing one, but the next time you hit spin, the process repeats itself from scratch – there is no reference to the previous spin or any other spins of the reels that have gone previously.

You could, theoretically, win at the progressive jackpot slots with two consecutive spins! Although when you think about the probabilities of, say, all five of the required symbols landing in place on back-to-back turns, you are more likely to win the lottery.

Every aspect of a slot game is governed by the RNG. The main set of reels are unpredictable and random, and so are your free spins should you be lucky enough to accumulate some. Even bonus games, in which you have to pick one or more symbols on-screen, are governed by the powers of the RNG to ensure complete fairness.

In layman’s terms, this is the process of randomness guaranteed by all slot games:

  • The player hits the spin button
  • The RNG produces a random number
  • Each reel relates to a digit
  • The reels stop on the assigned symbol
  • Sometimes you win, sometimes you don’t

How do I know that the RNG is fair?

Every online casino has its RNG software rigorously tested and monitored by an independent agency to ensure that it remains fair at all times.

This body, often the Technical Systems Trading (TST) team, provides certification for firms like us at Bitcasino, and also delivers peace of mind to players that they have an equal chance of hitting a winning spin every time they play.

Don’t forget, the RNG is hard-coded into the game, and so can’t be tweaked or manipulated in any way.

What’s the difference between the RNG and RTP?

Quite a few players get these three-letter acronyms mixed up, unsurprisingly.

The Return to Player (RTP) rate determines exactly how much a slot game will pay out when played an infinite number of times. It does not, however, determine when a slot game pays out. Ultimately, that’s the job of the RNG.

If the RTP rate of a slot is 96%, then that tells us that if one player tackled it until the end of time, they could expect to get 96% of their total stake back in winnings.

But of course, the point is that your individual session may return more or less than 96% – thanks to the RNG.

Random Number Generator FAQs

Many people understand the mechanics of an RNG, but occasionally they struggle to believe that it can deliver wholly unpredictable results.

Unfortunately, that’s a side effect of the bad old days of casino gaming, when nefarious owners would rig their slots to ensure that certain combinations never landed on the reels.

Happily, those days are gone in what is now a highly regulated industry, and online slots in particular leave players with that relaxed feeling knowing that the RNG cannot be hacked or manipulated in any way.

Here are some other common questions about the slots algorithm.

Can the RNG be cheated by the house?

Absolutely not: the algorithm central to RNGs is hack-proof and delivered hard-coded into each slot game, so there’s no tampering whatsoever.

All software developers are rigorously tested by independent bodies such as Gaming Laboratories International, whose role is to ensure complete fairness across the board.

Does the RNG have a memory?

No, the algorithm does not have the capability of storing information, and it does not have a memory chip in the normal sense of the word.

Contrary to the belief of the cynics, the RNG has no idea when it has produced a jackpot winner – it just keeps churning out numbers in a completely unpredictable fashion.

So in theory, I could win/lose ten spins in a row?

That is just about the size of it. Absolutely zero slot games are pre-programmed in any way, and so each session is played out in a completely random fashion. It’s the excitement that keeps us coming back for more, right?!

Now that you understand how online slots work, it’s time to spin the reels yourself. Login to your Bitcasino account today and you can try our slots for free or play for real cash!

Words: Sean McNulty
Images: Shutterstock


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