Online Casinos and RNGs: Understanding Random Generation
When you use an online casino, nearly every spin, card, or dice roll is created by a computer programme, rather than by hand. This may sound mechanical, but behind it is a carefully designed process that aims to make each outcome as unpredictable as possible.
This guide explains how that works in practice, using Random Number Generators (RNGs), and why they are an essential part of regulated UK online gaming. By the end, you will better understand what these systems do, how they are checked, and why their use is required under UK law.
How Do Online Casinos Generate Random Numbers?
An RNG is a software algorithm—a set of coded instructions—that generates numbers at very high speed, often thousands or even millions of numbers per second.
Each number is linked to a potential game outcome. When you press ‘spin’ on a slot, or select ‘deal’ in blackjack, the RNG captures the exact number being generated at that precise moment. That number determines what symbols appear or which card is dealt.
It’s important to know that these are not random numbers from a physical source, like rolling dice or shuffling actual cards. Instead, they are produced using a mathematical process called a Pseudo-Random Number Generator (PRNG).
PRNGs follow complex algorithms that produce outputs which, to the player and in statistical testing, behave like random results. They are called ‘pseudo’ because they are generated by a set of rules, but with safeguards to make them unpredictable in practice.
Why Are RNGs So Important in Online Casino Games?
Without an RNG—or without a trustworthy one—there would be no reliable way to keep outcomes fair.
For example, if you played a slot game where the results repeated every 10 spins, you could spot a pattern and predict when certain results might occur. That would give an unfair advantage to anyone who noticed it, and would undermine trust in the game.
In the UK, the Gambling Commission requires that all licensed remote casino operators use RNGs that meet strict fairness and unpredictability criteria. That means the sequence of results must pass recognised statistical tests showing that each possible outcome occurs as often as it should according to the game’s rules. This ensures games work as described in their pay tables or rule pages, which is essential for transparency.
Can You Trust That Online Slots Are Truly Random?
In regulated UK casinos, a slot game cannot be made available to players until it has passed independent testing. This testing checks not just that the RNG works, but that the game’s programmed payout rate—often expressed as the Return to Player (RTP) percentage—matches what is stated.
For example, if a slot advertises an RTP of 96%, that means that over a very long period of play, the game may return £96 for every £100 wagered, spread across all players. It does not mean each player will get back that amount, but that the results balance out to this figure in the long run.
Testing agencies simulate huge numbers of spins—often in the millions—to confirm that results are statistically consistent with this figure. They also check that no particular combination appears more often, or less often than it should. Only after this process is complete can the game be added to a UK-licensed site.
How RNGs Keep Online Casino Games Fair
RNGs are designed to produce results that are both unpredictable and independent. That means what happens in one spin, hand, or round does not influence what happens in the next. If the jackpot symbol appears twice in a row, that does not change its odds of appearing on the next spin.
UK regulations also require that RNGs be regularly re-tested to confirm they still meet the necessary standards. This is important because online games may be updated over time, for example to fix bugs or add features. Any change that affects the game logic must go back through testing before it can be re-released.
Are All RNGs in Online Casinos the Same?
The basic principle is the same—generate unpredictable numbers—but the way an RNG is set up can vary depending on the game.
A slot game’s RNG might be designed to map each number to a reel position, while a roulette RNG maps to the 37 or 38 possible outcomes on the wheel. Card games may need an RNG that simulates shuffling a virtual deck and removing cards as they are dealt.
Despite these differences, all RNGs in UK-licensed games must pass the same testing process. This means whether you are playing a digital slot, roulette, or blackjack, the RNG in use will have been certified to the same regulatory standard.
How Are RNGs Tested and Regulated in the UK?
The Gambling Commission sets the technical requirements for RNGs in its Remote Gambling and Software Technical Standards (RTS). These standards specify the qualities an RNG must have, including statistical randomness, unpredictability, and proper implementation of the game’s rules.
Testing is carried out by approved third-party laboratories. These organisations, such as eCOGRA, GLI, iTech Labs, and BMM Testlabs, have no financial interest in the game’s results. They examine the software code, the seeding process (how the initial numbers are chosen), and run long simulations to ensure results match theoretical probabilities.
Who Checks That RNGs Are Working Properly?
Before a game goes live, the operator must submit testing documentation from an approved test house to the Gambling Commission. Once live, games can be re-tested if there are updates, or at random as part of compliance checks. The Commission can request proof of testing at any time, and failure to comply may result in fines or loss of licence.
Test houses use recognised statistical methods—such as chi-squared analysis and serial correlation tests—to verify that no bias exists in the results. These methods help detect whether the RNG output behaves differently from what true randomness would look like over many rounds.
What Standards Do RNGs Have to Meet?
Under the RTS, an RNG must:
- Produce results that match the stated probabilities in the game’s rules.
- Be secure against tampering or reverse-engineering.
- Be seeded in a way that prevents someone from predicting future results, even if they know the algorithm.
- Operate independently of factors like bet size or time of play.
These standards ensure that the game you play behaves in line with the expectations set out by its published rules.
Is It Possible to Predict or Beat an RNG?
In a regulated UK game, the RNG is built specifically to prevent prediction. Even if someone understood the code, without access to the current seed value it would be virtually impossible to forecast the next output. This is why patterns seen over a small number of plays are usually just random coincidences.
There are no strategies that guarantee consistent winnings in games of chance like slots or digital roulette. The outcome is determined at the moment you play, and cannot be influenced by skill or by previous results.
How RNGs Work in Different Online Casino Games
Slots
When you press ‘spin’, the RNG selects a number for each reel. These numbers correspond to reel stops, which decide the symbols you see. Whether the result is a win, loss, or bonus feature is decided instantly before the reels visually stop.
Table Games Like Roulette and Blackjack
For roulette, the RNG produces a number that corresponds to one of the possible positions on the wheel. In blackjack, the RNG creates a freshly shuffled virtual deck for each hand and then deals the cards from that new order. This means every hand is generated independently, with no link to previous ones.
Explore Casino Games Online at Rose Casino
At Rose Casino, you’ll find a wide selection of online casino games such as slots, roulette, and blackjack—all operated under a UK Gambling Commission licence, ensuring everything meets the highest standards for player protection.
Navigating the Rose Casino site is straightforward, so you can quickly find games that match your interests. Log in or sign up to see the options available, and pick the games you’d like to try.
Slots and table games at Rose Casino work just as described above—using certified RNG software to guarantee fairness on every play. Always remember to play within your limits and enjoy the peace of mind that comes with a safe and regulated site. Please play responsibly.
*All values (Bet Levels, Maximum Wins etc.) mentioned in relation to these games are subject to change at any time. Game features mentioned may not be available in some jurisdictions.
**The information provided in this blog is intended for educational purposes and should not be construed as betting advice or a guarantee of success. Always gamble responsibly.