How Do Online Slot Machines Work?

Slot machines don’t inspire a lot of trust in people. As popular as they are, it’s not uncommon for people - especially those who are experiencing a losing streak - to wonder if slot machines are rigged against them, and this is largely because a lot of us simply don’t understand how they work.

To be clear, slot machines aren’t rigged (we’ll go into this in more detail later on) - they have to adhere to certain standards to be accepted by the Gambling Commission.

But the principles they work on can be confusing, and in most cases they’re specifically designed to manipulate the customer into continuing to play for longer than they intended.

In this article, we’ll explore all aspects of the workings of slots. By the time you reach the end, you’ll not only understand how to play slots and how they work, but be in a position to actually make some money from them. So let’s dive in!

Slot Machines History And Overview

In real life

The earliest precursor to the slot machines was invented in 1891 in New York, and was based on poker.

You would insert a nickel into the coin slot (from where the term ‘slot machine’ originally comes), pull a lever on the machine, and five drums would spin before displaying five card faces. The aim was to end up with a good poker hand.

You wouldn’t win any prizes automatically; instead, the establishment that owned the machine might offer free drinks or cigars, but it would depend entirely on what that particular establishment had on offer.

This system had some obvious flaws - particularly the lack of any automatic payout mechanism - and it wasn’t long before a new machine was designed to fix them.

Just a few years later, a much simpler mechanism was used to design another machine in California, with three spinning reels displaying a total of five different symbols.

This reduced the number of possible combinations considerably, making it possible for automatic payouts to be made. The highest of those, awarded if you got three bell symbols in a row, was 50 cents.

Gambling machines gained popularity with great rapidity, despite frequently getting on the wrong side of the law in the USA, and being nicknamed ‘the one-armed bandit’ thanks to their habit of taking a customer’s money.

In the 1960s and ‘70s, machines started to move to an electronic model, with the traditional side lever either redundant or abandoned altogether. Video slots were also developed in the 1970s and soon became highly popular in Las Vegas.

By this point, physical slot machines had become roughly as we know them today.

Online

Random number generators were first developed for use in slot machines in the 1980s, long before the advent of online slot machines, to allow for a higher number of possible outcomes, and thus the possibility of offering higher jackpots for the rarest combinations.

The first internet casinos were launched in the mid-1990s, featuring the earliest online slot machines, which mostly came in the form of adaptations of physical slot machines.

Casino operators quickly grasped the potential of this new platform, and investment in developing the technology rocketed upwards. Developers began to add in advanced graphics, sound effects and animations, as well as new features, such as progressive jackpots.

Themed slots soon came into existence, adding even more potential for variety and allowing developers to move away from the generic fruit, numbers and bell symbols that slots had begun with.

And of course, as soon as the internet became available on mobile phones, so did slots. In 135 years, players have gone from asking at the bar for the free beer they’d won to having the possibility of winning literal millions while on the bus. Who knows where technology might take slots next?

Types Of Slot Game

Classic

The traditional form of slots game, which usually features five reels these days rather than three - although you sometimes see variations of this number, as in the game above. Generally speaking, you win by matching at least three symbols in a row from left to right.

There are many, many variations on the classic slots format, with a wide range of bonus features and mini games, but the essential principle remains the same across all slots in this format.

Megaways

Megaways slots games add an additional level of excitement and unpredictability by varying the number of lines there can be in the overall grid, thus drastically increasing the potential number of paylines.

Megaways slots tend to have prominent declarations of the number of possible paylines, such as ‘118,000 ways!’, but this doesn’t generally translate to a higher chance of winning (much as the game might like you to get that impression).

Some megaways slots will also have a cascade feature, where matching symbols will be removed from the board, allowing new ones to take their place, with the possibility of further wins.

Grid

This is a less common form of game, where symbols are arranged in a large grid. Often, clusters of matching symbols will result in a win, but you’ll also find some games where a certain number of matching symbols, positioned anywhere in the grid, earns you a reward.

Cascade features may be found in grid slots games too, some offering progressively increasing amounts for several wins in a row.

Important Concepts For Slots

When it comes to the actual mechanics of slots, there are a number of crucial concepts you need to be familiar with. We’ll talk you through each of these below.

RNG

RNG stands for ‘Random Number Generator’, which is the algorithm behind all modern online slots.

RNG software is behind every single spin of a slots game. Each symbol on a reel is represented by a number, and for every spin the RNG generates a sequence of numbers which will determine the results you see on your screen.

It’s important to be aware that each symbol is not given equal weighting by the algorithm. More valuable symbols will be weighted less heavily, meaning they’re less likely to appear compared to symbols that will result in a smaller payout.

This means that, of all the possible combinations of symbols, those resulting in a larger win will appear less frequently, without the randomness of the result being compromised.

RTP

As you may well be aware already, RTP stands for ‘return to player’, and indicates the average percentage return a player will receive compared to their wagering. Usually, this will be indicated somewhere in the info or help section on a game - although unfortunately this isn’t universal.

Typically, slot games will offer RTPs in the 90% - 98% range, meaning that players can expect on average to receive 90p-98p back for every £1 spent.

You may be wondering how it’s possible to guarantee a specific RTP if a slots game is using an RNG to power its software. Well, the important thing to keep in mind is that RTP isn’t calculated over hundreds or thousands of spins, but over millions.

You’ll see a lot of variation on a smaller scale, but statistically speaking it’s not hugely difficult to weight the symbols for a slots game so that they will work out to a particular average RTP.

On a large enough scale, you can be pretty confident that the RTP will conform to expectations.

However, that doesn’t mean that you personally can expect any slots game to return an amount that corresponds to the RTP when you play. Unless you devote an absolutely enormous quantity of your time to it (which we definitely do not recommend), you won’t reach anywhere near the number of spins required to see the expected return.

And besides, even if you did manage to hit a game’s exact RTP, you’d still be making a loss of several percent anyway.

Volatility/Variance

Volatility and variance mean essentially the same thing - how wild the swings can be between losses and wins.

A game with high volatility is generally less likely to pay out on any individual spin, but more likely to pay out a larger amount if you do win. Slots games with high volatility promise the higher chance of a large win in a shorter space of time, but you’re less likely to pick up smaller wins in the meantime.

A low volatility game, meanwhile, is the opposite. Large wins are less common, but you’ve got a better chance of hitting a smaller win on each spin.

Edge

The edge (also known as the house edge or margin) is the bookie’s profit on a slots game. If a slots game advertises an RTP of, say, 96.2%, then the remaining 3.8% is the bookie’s edge, and where they make their money.

Because their customers collectively make enormous numbers of spins on each slots game, a bookie can rely pretty confidently on their edge to be consistent, meaning that slots games offer them reliable profits with very little effort on their part.

Paylines

Paylines refer to the positions matching symbols must hit for the game to award a win. For many games, at least three matching symbols running from left to right and in adjacent lines will result in a win, but this can vary significantly from game to game.

You can check the paylines for a game from within the in-game info section.

Paytable

The paytable, meanwhile, tells you the amount awarded for each possible winning combination of matching symbols. This too can be found from within the in-game info section.

Jackpot

Some games will feature progressive jackpots (and this will usually be shown very obviously), which will generally be won at random on any spin (even a losing spin).

Jackpots are typically shared between multiple slot sites (and sometimes also across multiple games), and grow in size with every spin of the reel, because a small percentage of a player’s bet goes towards funding that jackpot.

This means that the effective RTP of that game is reduced by the contribution to the jackpot.

You’ll often see smaller jackpots that ‘must be won’ by a certain day or time, or before a jackpot reaches a certain amount.

This produces the impression that hitting a jackpot is more likely than normal - and admittedly, the chances of winning a jackpot do tend to increase as the sums increase.

But you should keep in mind that the likelihood of any one person winning a jackpot is vanishingly small. You certainly shouldn’t keep playing for no other reason than a jackpot being due to pay out.

Bonus features

More and more kinds of bonus feature have been developed as online slots have become more sophisticated, with the aim of upping the excitement of play, which can become a little repetitive with nothing but symbol matching to entertain you.

Some of the most common are as follows:

• Scatter (free spins). Three matching scatter symbols (or free spins symbols in some games) rewards you with a certain number of free spins - typically ten, although this can vary. You’ll also often encounter additional bonuses during your free spins, which may increase the chances of winning, or potentially add to the number of free spins.

• Lock & spin. Usually, these features are triggered by getting a certain number of special symbols in one spin (e.g. at least 6 coins). The game will then give you three spins to fill in the rest of the grid, resetting each time you add an additional symbol. The feature ends when you either run out of spins (and you then win the amounts shown on the symbols) or when you fill the entire grid, generally winning a small jackpot.

• Cash drop. When you receive three ‘cash drop’ bonus symbols in a spin, you get the chance to collect extra cash which ‘drops’ from the top of the screen - hence the name. You may also be awarded an extra bonus amount at the end of the feature.

• Expanding reels. Less commonly, you may encounter an expanding reel bonus feature, where each win adds a new line to the game, further increasing your chances of winning again.

• Mini jackpots. With this kind of bonus, any spin can trigger a bonus round that gives you the chance to win a bonus pot. Pots will often be labelled from ‘mini’ to ‘mega’, and you’ll turn coins or match symbols to determine the pot you receive.

Who Makes Slot Games?

Dedicated slot developers spend their time creating new slots games and licensing them to bookies and casinos. Some of the best known are NetEnt, Red Tiger Gaming and Microgaming, but there are hundreds of others out there.

Exactly how they make their money can vary, depending on the developer. The biggest developers with the most popular games are in an advantageous position, and may be able to demand a cut of a bookie’s profit from a certain game.

Smaller developers of games that are less in demand are more likely to license their games for a certain period for a one off fee.

Some bookies and casinos also have their own in-house development teams, allowing them to add to their range of games without having to shell out for licences.

Are Slot Machines Fair?

Yes…

Slot machines are regulated by the Gambling Commission, and are legally obliged to meet certain standards. Tests must be made and reports sent to the Gambling Commission to verify that the games are working as stated, and information must be provided to the player about how the game works and the chances of winning (although displaying the RTP isn’t strictly required).

Online betting sites must comply with these standards to retain their gambling licence, so you can be confident that any UK licensed bookie is at least meeting the minimum requirements, and that the game in question does meet its advertised parameters.

In other words, if you’re playing with a UK licensed bookie, then your slot game isn’t rigged against you.

But also no

However, that doesn’t mean that bookies play fair. Slot games are specifically designed to play on human psychology, with everything from the graphics, sound effects and mechanics intended to entice you into continuing to play.

The house always wins. Most people have heard this maxim in regard to casinos, and it’s just as applicable to online slots. On average, you’ll always lose more than you win when playing slots - otherwise, a bookie couldn’t make any money.

Of course, you could always get lucky, which is exactly what most players of slots are hoping for, but the odds are against you. In most cases, a slots player is simply giving away their money in exchange for nothing more than the hope of a big win.

Can You Profit From Slots?

However, there is a way to improve your chances.

Bookies and casinos are always working to draw new customers in, and that usually means offering up free spins and bonuses to new and existing customers.

One way to take advantage of sports offers is Matched Betting, but it’s possible to profit from casino offers too.

If you factor in the value of those rewards (based on the RTP of the slots in question), you can end up in a position where, statistically speaking, you can expect to make more money than you wager.

For example, we’ll take a look at Betfred’s casino welcome offer: stake £10 to receive 200 free spins.

You have a number of options for slots games to stake your £10 on, but we’ll assume an RTP of 96%, which is at the higher end but shouldn’t be difficult to find. Based on the RTP, we would expect to receive back £9.60 from our £10 wagering on average.

We then receive 200 free spins, each valued at £0.10 per spin - making an effective value of £20. If you use those spins on Fishin’ Frenzy, which has an advertised RTP of 96.12%, you would expect to make £19.22 from your free spins on average.

The expected value of this offer is therefore £18.82, taking into account a 40p loss from our initial wagering, as you can see in the results from our EV calculator:

Now, as we’ve learnt in this article, you can’t expect the RTP to precisely determine your actual profits on a relatively small number of spins.

However, if you complete multiple casino offers, all of them with positive EV, you’re extremely likely to end up in profit. You’ll see ups and downs, but most likely end up with your profit tracking fairly closely to the expected EV of all the offers you’ve completed.

Of course, there is also a possibility that you could lose your £10 stake and win nothing at all from your free spins - but, especially with an offer of this generosity, that is very unlikely. And the more offers you complete, the more your profits should correspond to your overall total expected value.

Some of our most successful members make the bulk of their profits from casino offers - and although they’ll have ups and downs, they end up making consistent profits.

Summary

Slots machines have come a very long way from the early days of physical coin slots and levers, but they’re more popular than ever. Bookies love slots, because from their point of view, the profits are incredibly reliable, and the gameplay itself is addictive.

Without any offers going at all, slots are little more than a flashy way to waste money. However, it’s perfectly possible to put yourself in a position to profit from slots-based offers in the long run.

It’s important, though, to be aware that there is always some risk involved. You’re never guaranteed to win money, and if you’re prone to gambling addiction then slots can be particularly dangerous.

However, if you’re confident you can do so safely, slots offers give you the opportunity to make solid, consistent profits.

Outplayed’s diamond membership includes complete detailed guides to nearly 150 casino signup offers, plus daily casino reloads. If you’re interested in signing up, check out our membership options, or contact us to find out more!