The simple formula of casino slots has been a hit for decades. Once simple mechanical devices with a lever, today they are the most popular and largest game category in the online casino world. How exactly do online slots work and how is it determined which symbols you see on your screen? In this guide, you will learn everything about how a slot machine works and the software behind it all: random number generators (RNGs).
How does an online slot work?
To play a slot with real money, you need an account at an online casino. When you open an online slot, place a bet and press the spin button, a random combination of symbols appears on the reels. Usually, the aim is to form three or more matching symbols on a payline. Other games use different ways to win, such as clusters of symbols that are adjacent to each other or bonus features.
Which combinations result in a prize and how much they pay out is predetermined in the slot’s rules and paytable. Some slots also contain additional features, such as Wilds, multipliers and bonus rounds, which can provide additional winnings.
How are online slots made?
Before a provider creates a new slot, the team first researches what is already on the market, which trends are popular and what players find interesting.
This research results in the concept, including the theme, design, mechanics and bonus features. The provider tries to create a game that appeals to the target audience while also standing out from existing slots. Programs that help with the design include HTML5, Photoshop, After Effects and 3ds Max, among others.
At the foundation of every online slot is a mathematical model which has all the core information of the game programmed into it. For example, how often each symbol appears on the reels, which combinations count as wins, how many reels or paylines there are and other properties like volatility. The outcomes of the spins are determined by an independent system: RNGs, also known as random number generators.
What are RNGs and how do they determine the outcome?
An RNG is software that continuously generates numbers. This happens not only when someone is playing, but continues even when no one is spinning the reels.
Each number is linked to a specific symbol and position on the reels. When you press the Spin button, the number generated at that moment determines which symbols appear where on your screen.
Which number is linked to which symbol also changes constantly. This means that every spin is independent of previous results and it cannot be predicted which combination will appear on the next spin.
How fair are RNGs?
An RNG is designed to ensure that the outcomes of an online slot are random and unpredictable. At regulated online casinos, RNGs are also tested by independent testing laboratories.
These labs analyse large quantities of results to check whether the RNG actually functions randomly. An important requirement is that the software does not show any patterns. Checks can also take place after a game has been released. This allows casinos to verify that the software continues to function as intended.
It is therefore important to play at a recognised and licensed online casino. This way, you know that the game and software must comply with the applicable rules.
What are RTP and volatility?
In addition to the RNG, there are other technical properties that determine how a slot behaves. Two important terms are RTP and volatility.
RTP stands for Return to Player and indicates what percentage of bets a slot theoretically returns in the long term. A slot with an RTP of 96%, for example, has a theoretical return of €96 per €100 in bets, viewed over a very large number of spins. RTP is a long-term expectation and says nothing about the outcome of an individual spin.
Volatility indicates how often and how large the payouts of a slot are on average. In a slot with high volatility, larger wins may occur less frequently, while a slot with low volatility may provide smaller payouts more often.
The RTP of a slot comes from the mathematical model of the game. All the components of a slot together determine how much the slot theoretically returns in the long term. RTP is therefore the result of the calculations behind the game.
How do bonus features work?
Many online slots contain additional features, such as free spins, Wilds, multipliers and bonus rounds. These features are programmed in advance and form part of the mathematical model of the slot.
When you start a spin, the RNG first determines the outcome. If, for example, enough Scatter or bonus symbols appear on the reels, the software registers that the conditions for a bonus feature have been met. The system then activates the corresponding feature.
With free spins, for example, the number of spins you receive, which symbols function as Wilds and whether multipliers are included may all be predetermined. The unpredictability of the outcomes is part of how every slot works.
Frequently asked questions
Can you try online slots for free?
Yes, most casinos allow you to try a demo version. You do not need an account for this. In demo mode, you play with a virtual balance.
Is every spin completely random?
The outcome of every spin is determined independently by the RNG. This means that previous results have no influence on the next spin.
Can a slot know when you have lost a lot?
A regulated slot should not adjust the outcome based on your previous losses or wins. The RNG determines the outcome according to the predetermined game mechanism.
Can I play online slots on my mobile phone?
Yes, many online slots are available on smartphones and tablets. The software adapts to the screen, allowing you to use the reels and game interface on mobile devices as well.
