How are slot games coded and programmed to be compatible with your mobile phone?


There’s no denying the fact that we’ve been on quite a journey with the smartphone since it first appeared back in around 2007.  Before then our phone was just that – a phone for making calls, sending text messages and maybe even playing the most basic of games like Snake.

But before long those mobile games started to become a whole lot more complicated, and more and more people started to play them on their phones.

And, by 2018, mobile gaming had all but taken over leaving consoles and PCs in its wake. So now even games that were major successes on these bigger screens are being played on mobiles, with very little being lost in terms of player experience and enjoyment.

It’s not just in the world of video games that this revolution has been taking place, it’s happened with online casinos too.

A brief history of online casinos

The first of these started to appear in the 1990s just as the internet was also starting to get off the ground. Initially, these also just featured fairly basic games like roulette and blackjack that needed simple coding and programming and unsophisticated design.

As time went on these became more complex – and they also started to be available to play on smartphones.

The big benefit for players was the sheer convenience. They could play their favorite games virtually wherever and whenever they wanted, all they needed was a wi-fi network to connect to. In the drive to make the online experience as lifelike as possible, the concept of the “live casino” was born. This involved the streaming of live games of roulette, blackjack, and baccarat run by actual dealers direct to a player’s device.

Where slots fit in

But for all the casino table games, it was the slots games that have always been the big money-spinners (pun not intended!) for the online operators.

There are plenty of reasons for this with the first being just how simple they are to play. You simply chose a stake, press “play” and away you go. The reels spin and you either win or you don’t – it’s as easy as that.

The fact that the games can be given any one of a countless number of themes also makes them appealing to a wide range of potential players. So, some might want to go chasing the gold at the end of a rainbow while others might want to play a game themed around a favourite movie or TV show.

To make them even easier to play, most of the big names in the online casino world also worked quickly to create smartphone apps. That’s why today, to find an app, you just need to have a little look around online and you’ll be spoilt for choice with many ranging from online slot providers to poker providers and generic casino providers. What’s more, once you’ve downloaded one it will probably qualify you for some fairly generous welcome bonuses too.

Mobile Apps

The coding behind mobile slots

Slot games are one of the most popular online casino games. For all their seeming complexity, the actual coding behind a slots game is relatively simple. Within each game, there is a pre-determined pay-out that is triggered whenever a certain combination of symbols lands in the correct pattern.

Creating the code to do this is logical and straightforward. The more complex element comes from how the random reel spins are generated. The engine behind this is the same as the one that drives all online casino games – the random number generator, or RNG.


This is an algorithm that “decides” on the position that reels will stop after each spin. Because this is a software program it still has to follow a set of rules so it can’t be described as being random – so the more accurate term for them is a pseudo-RNG.

True RNGs do exist, including a particularly intriguing one that uses the unpredictable motion of lava lamps to create genuinely random and unrepeatable sequences. But, for the online casino, a pseudo version that goes through millions of different permutations before repeating itself is quite sufficient to ensure fair play.

There are two other elements that need to be incorporated into the coding for a mobile slot. The first of these is the Return to the Player and the second is its volatility level.

As the name suggests the RTP is the amount of stake money that is returned in the form of prizes. So, a machine with a 95% RTP will return 5% of the money players use. It doesn’t mean that every player will receive 95% of their stake money – it is simply the average over a set period of time.

The volatility of a slot refers to whether it will tend to make numerous lower pay-outs if it has a low volatility or fewer, larger ones if it’s a high volatility machine. This also has to be programmed into the coding.

Some games also have what is known as progressive jackpots. These work by linking numerous different slots together with one major prize fund. This can be won by a player on any one of the participating machines, and it can run into a six-figure sum or more.

So, the coding for a big win like this also has to be built in.

Beyond this, the appeal of the slot is also all about the way it looks and plays – but that’s a whole different story that the designers will be able to tell you about!

Pankaj Kumar
Pankaj Kumar
Articles: 207