How Do Online Slot Machines Work?

Slot Machines

There are a ton of misconceptions and myths about how online slot machines operate. Perhaps you believe that they are rigged in favour of the casino. Or maybe you want to learn the nitty-gritty of the slots to start winning at the game. Whatever your reason, you’re in good company.

We’ve written a bunch of articles on how to win at online slot machines. In this guide, we’ll focus on how these amazingly popular casino games work. Wondering what’s under the hood of online slots? Hint: read on.

First Things First: Types of Online Slot Machines

While there are millions of slots available to play at online casinos, all of them fall under a few categories. Classic slots, video slots, 3D slots, 3-reel slots, 5-reel slots, and progressive jackpot slots are some of the popular. There is an assortment of other slot styles that are less known but also available to play. Talk about free spin slots, X/Y bonus slots, multi-level bonus slots, and other unique slots. The secret to winning at slots is to choose an online casino that offers a huge variety. It’s easier this way to snap up a slot that offers high payouts (RTP). Good thing, we have done all the research and handpicked the best online casinos to play slots. It’s not uncommon to find free spin slots, X/Y bonus slots, multi-level bonus slots, and other unique slots.

The concept of Virtual Machines

For all intentions and purposes, slot machines run purely on math. Or algorithms, to be precise. That goes for just about any online casino game, from roulettes to scratch cards. But then again, a slot machine has to be a game of chance. Isn’t that the central tenet of casino gambling? That’s exactly where the concept of virtual machines come into play.

Even the earliest versions of slot machines were designed around virtual machines. These are program codes comprising symbols (typically in the range of 10 to 15). These symbols are programmed into virtual arrays (or group of arrays). The arrays actually tell the machine how to populate symbols on the reels (randomly). The larger the virtual array, the more random the reels are populated, and the better the slot.

As you might expect, low-value symbols tend to appear more frequently than high-value ones. That’s where the so-called Odds Table comes in handy. This is a nifty feature under the hood that determines the payout for any particular combo of symbols.

Understanding the Random Number Generators

Usually shortened as RNG, the Random Number Generator is a computer code (algorithm) whose primary purpose is to generate random sequences in a split of a second. In essence, it’s the RNG that churns out random and varied sets of numbers whenever you spin the slot machine. They essentially determine the outcomes of every slot machine spin. And they deliver them randomly despite the last outcomes.

So, how do RNGs work? Glad you asked. In land-based casinos, an RNG is often embedded as a chip with accompanying software installed in the machine itself. Its singular job is to compute large bytes of numbers in a snap. What it does is put 1 or multiple numbers into the so-called register. This is much akin to a lottery pot where you can pick random balls/pieces of paper. The slot machine, on its end, picks one of the numbers from the “basket” and informs RNG of the same.

But that isn’t all. The RNG actually goes back, generates more numbers, and replenishes the register. The process goes on and on. That’s all the random number generator does. In practice, slot machine developers are not the ones that program the algorithms for the RNG. It’s always prudent and more transparent to contract an independent developer.

How do the numbers generated by RNG look like?

You’d be forgiven for thinking they’d look like random integers e.g. 3568542. In reality, numbers delivered by RNGs are usually small numbers, some way smaller than 1. Don’t be surprised to find random numbers like 0.003529689 or 0.76197262. It’s not even uncommon to also find integers raised to the power of negative E value such as 26563^-3e.

What happens when you click “spin” is truly amazing. If you’re playing a 3-reel slot machine, for instance. The slot needs 3 set of random numbers for the reels. What it does is call for 3 random numbers from the register and tell the RNG of the same.


What goes on behind the scenes of slot machines is truly magical. It’s a cog system composed of slot software, RNG, virtual machine elements, and a lot more. You’re better off starting your online casino journey with our comprehensive guide to slot machines.

BONUS READ: Slot Tournament Tips and Tricks That Everybody Should Know

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