How Do Slots Work – The Mechanics Behind Them

Learn how a slot machine works, from basics to complicated mechanics, we cover them all! Check out the latest online slot machine mechanics introduced by top developers.

If you’re a casino player, you know that slots are fan-favourite games, played by millions of players all across the globe. The main reason for that is, these are some of the easiest games to play.

You’re basically just pressing the Play Button and you have to do nothing but wait for the win to occur. And while this was the rule way back when slots were first introduced, today, there’s so much more to them.

So much is happening in the background of what you’re seeing when you start playing a slot game. When slot developers create these games, they need to pay attention to so many details. We’ll cover all of these details here, to give you an insight into how slots actually work and what happens when you press Play.

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What Is a Slot Machine?

A slot machine is a casino game of chance, meaning a game where you have little to nothing to do with its final outcome. It is a game that contains reels and rows, known as the grid, filled with symbols.

The number of reels can be anywhere from 3 to who knows how many since nowadays developers create slots with a limitless number of reels. The same goes for rows; these could be many, depending on the slot and its mechanics. We’ll go into detail soon.

For now, you should also know that the patterns in which symbols should land to create a win are called pay-lines. Now, in contemporary slots, even paylines have changed, as you will soon see, and they’ve been replaced with ways to win, blocks, clusters and whatnot. We’ll also cover these in short.

How Are Wins Achieved?

You now know how slots are designed. The next thing to learn is how they give out results, really. Well, all slots work on a Random Number Generator, which is a device that has an algorithm generating different symbol combinations and completely, 100% random game results. This is why Slots are games of chance since you have no control over the outcome. The RNG will make the game randomly choose the symbols that land on the reels, and if these match, you win, if not, you lose. As simple as that.

The Math Model

Other factors that weigh in are involved, too. You have the math model. Each slot game arrives with pre-set hit frequency, volatility and RTP (Return to Player Percentage), contributing to the overall payout potential.

The hit frequency and volatility are intertwined. These two tell you how often a win can land on the reels. A slot machine can be low, medium or highly volatile. Low volatility slots give payouts often, meaning they have a high hit frequency rate. The payouts they give, though, are far lower than in medium and high volatility slots.

The medium, as suggested, are slots that give payouts less frequently than low but more frequently than high volatility slots. They have a medium hit frequency rate. The payouts they give are decent. Now, high volatility slots are the most exciting to play, since while they don’t give out payouts that often when they do, these payouts are really life-changing.

The Mechanics Behind Slots

Each developer chooses the mechanics they would base their slot machine on, in order to calculate the payouts that particular slot should be able to pay out.

Otherwise known as the engine, the mechanics is basically the machine behind the slot. It consists of the number of reels, rows and pay-lines offered, which we covered, but also of the Hit frequency, Volatility and RTP. All of these combined together affect your gameplay, and the final outcome of the game.

Depending on the mechanics offered, as said, a slot can have 3, 5 or countless reels, for instance. It can have paylines or other patterns like Cluster Pays, for example. The number of pay-lines, rows, reels, symbols present on reels and their size… they contribute to the final outcome of the game. That’s why today, you’ll find so many different types of mechanics, to be covered below.

Modern Types of Mechanics

As you could see, slots can come in all shapes and sizes, and that’s exactly what makes them so attractive to players. And that’s what makes developers go out of the way and work hard at finding new and innovative ways to keep players engaged and make these games even more fun and appealing.

They try to introduce thousands of new ways to win instead of sticking to the standard 5×3 grid with 20 pay-lines, which is the basic slots model. Here, you’ll discover several popular mechanics that are offered in slots nowadays.

1. Megaways

Megaways is a highly volatile mechanics designed by Big Time Gaming and launched in 2015. This is an engine that usually offers 6 reels with a growing number of symbols appearing on them, from 2 to 7 symbols on each spin, allowing for up to 117,649 ways to win. Meaning, you won’t get regular paylines to land wins on, but many different combinations, ways to land a win.

2. Cluster Pays

Cluster Pays mechanics was first introduced by NetEnt, in 2016, with the game Aloha: Cluster Pays which became an instant hit. It’s been years since we first saw this amazing engine where you need to be landing symbols in clusters of several to get a payout. The bigger the group of symbols you land, the better the payout.

3. MegaClusters

Big Time Gaming is the name behind another exciting engine, the MegaClusters, taking the Cluster Pays mechanics to the next level. This engine premiered in the slot Star Clusters in 2020, where the expanded grid can hold up to 256 symbols at a time, allowing for massive rewards to be scooped.

4. Splitz

Splitz is a mechanics debuted by Yggdrasil in the slot Temple Stacks in 2020. Here, special symbols can split and form longer lines or clusters, if we may, allowing for huge prizes to be won. The symbol can split into a random number of instances, so you should expect really life-changing rewards due to the many symbols present on the grid.

5. GigaBlox

Instead of splitting symbols, this mechanics stacks several symbols in order to provide one giant symbol on the grid, sized 2×2 to 6×6. The symbol gives out payouts according to the number of spaces on the grid it covers, again, allowing for staggering winning potential. It was debuted in 2020 by Yggdrasil, right after the Splitz mechanics, with the launch of the slot Lucky Neko GigaBlox.

6. Infinity Reels

Presented to the world in 2021 with the launch of the slot El Dorado Infinity Reels, this is a mechanics that was inspired by the Megaways engine, since it allows for new reels to be added to the grid, following a win, having no set limit as to how many new reels can be added in total. It greatly improves your chances of winning big, thanks to the infinite reels and symbols they contain.

The Features

Now, while slots way back were quite simple and straightforward to play, as mentioned, they’ve evolved and changed completely nowadays, since developers are going out of their way to make them more interesting for players.

Today, slots are packed with features. You’ll rarely find a slot that offers no special feature or bonus round. So, we’ll cover the basic features offered in slots nowadays, but bear in mind that you’ll find hundreds of other different features in slots you’re seeing being released today.

1. Wilds

Wilds are symbols offered in a slot game which usually have the role of a substitute. You can think of them as jokers in popular card games. These are the symbols that will help you achieve a win when you’re lacking a symbol to create a matching winning combo. Wilds come in many different forms and can play other roles, too, but the substituting role is their trademark role.

2. Scatters

While known to play many other roles, Scatters are best known for helping you trigger bonus rounds. These are special symbols offered in a slot that can also give payouts on their own but are usually introduced to help you get into a bonus round.

3. Free Spins Feature

The Free Spins Feature is the most popular bonus round, and the favourite among players. This is, as implied by its name, a bonus round where the spins you’re playing are free; you won’t be paying for them.

What’s so appealing is that during the bonus round, the action happens. This is where you get different modifiers like Multipliers, cash prizes or even Jackpots, depending on the game. And that’s why players are super-eager to trigger it the fastest they can.

4. Bonus Buys

Related to Free Spins feature or other bonus rounds offered in the slot, comes the Bonus Buy feature. This is actually one of the few features that give you a bit of control over the slot game.

Using the Bonus Buy option, you can purchase your way into the much-wanted Free Spins or other bonus rounds where the biggest payouts can be won.

Bonus Buys, offering this control, are not offered across all jurisdictions, though, since they further contribute to your gambling, and are in some jurisdictions forbidden, as part of responsible gambling rules.

5. Gamble Feature

The Gamble Feature allows players to double, triple or multiply their winnings by placing a bet either on Black or Red cards as well as on High and Low Cards. This is one of the oldest features seen on fruit slot machines and is one of the most simple and played amongst them all.


  • Slots come in many shapes and sizes;
  • Innovative engines offer better payouts;
  • Different mechanics types exist;
  • You are given the freedom to choose the slot by checking its mechanics.


  • Often hard to comprehend how to play a slot;
  • Many mechanics offer volatile math models.

Slot Machine Mechanics FAQs

Slots are games of chance, so the outcome would depend on pure luck. Sure, you can have some features, like Bonus Buy bets, which could give you small control over your play, but eventually, the results will solely depend on luck, and of course, the Random Number Generator.

Yes, actually, you can. You’d need to go to its paytable, and the RTP and volatility are written at the bottom usually. Developers are transparent when it comes to these things, so before you start playing a slot, make sure you check for the RTP and volatility, to see whether it is a game suited for you and your budget.

Yes, indeed, you can. Online slots today are designed in HTML5, so regardless of the device you choose to use, a desktop device, a smartphone powered by iOS or Android, or a tablet, you just need to connect your device to the internet and load the slot.

No, not really. When slots first appeared online, you needed to have Flash and download them to play them, however, today, thanks to their HTML5 format, online slots do not need downloading. You just need your device to be connected to the internet.

Basically, yes. You’ll rarely find a casino where slots are not the star games, in fact.

Slots, to be offered across jurisdictions, go through extensive vetting procedures. Not only do they need to get the green light from the regulators, but they also need to go through auditing services like iTechLabs and eCOGRA. These are auditors that make sure the slot runs on an RNG and is completely fair and random to play.

You can visit the paytable in the search for answers since developers explicitly and transparently display all the info about how their slots work. However, don’t worry, because any time you form a win, it would be flashed and highlighted on the grid, and added to your total, so you can be certain you’ve won something.

We cannot pinpoint one and be biased, because there are so many different slot engines available on the market today. Sure, Megaways was the revolutionary one, the pioneering mechanics that changed slots for good, but that doesn’t mean that this is the best one. After all, it depends on individual players’ interests and preferences.

Not necessarily. The volatility would depend on the rest of the components of a slot, hit frequency, RTP, symbols and features, all of which contribute to the final outcome. And even though most will, not all modern-day slots will be highly volatile.

As said, slots are games of luck, regardless of the mechanics they’re using. Sure, some may be easier to play and scoop payouts from while others harder, but that still doesn’t deny the fact that these slots run on a Random Number Generator and can only deliver random results and game outcomes.

There sure are! Since its launch in 2020, the MegaClusters mechanics has been used in several slots, such as Star Clusters, All MegaCluster, Cyberslot, Kluster Krystals, Millionaire Rush, Diamond Fruits, etc.

C Grand
C Grand

Chris GrandCasino & Games Reviewer

As a content writer specializing in iGaming, my goal is to keep players informed about the latest industry trends and game releases. I also strive to deliver honest and insightful content that adds value to players' experience.