RNG: The beating heart of the online casino

Invisible but omnipresent, the Random Number Generator (RNG) is the software engine that guarantees the fairness of every slot machine spin or online card deal. Contrary to popular belief, this system has no memory and generates thousands of results per second, making prediction impossible. Understanding how it works is the only way to distinguish players’ myths from the mathematical reality of casinos.

For the average player, pressing the ‘Spin’ button is the action that starts the game. For a technical expert, this click is simply a request to display a result that was decided a fraction of a second earlier. RNG (Random Number Generator) is the cornerstone of the gaming industry, used in both classic video games and online casino games.  

What exactly is RNG?

RNG replaces the croupier who physically shuffles the cards or the gravity of the ball in roulette. To be more precise, it consists of complex algorithms that replace chance. 

PRNG vs TRNG: The crucial technical distinction

It is crucial to distinguish between two technologies that are often confused, even by some professionals:

• TRNG (True Random Number Generator): Used mainly in land-based casinos or for high-security cryptography. It is based on unpredictable physical phenomena (atmospheric noise, radioactive decay or thermal noise). It is pure chance, linked to physics.
• PRNG (Pseudorandom Number Generator): This is the standard used by online casinos. It is a mathematical algorithm that requires an initial value called the ‘seed’.

Although the term ‘pseudo’ may be cause for concern, modern PRNGs (such as the Mersenne Twister algorithm) are so sophisticated that the sequence of numbers generated is statistically indistinguishable from true randomness. Without knowing the initial seed and the exact algorithm, it is humanly and computationally impossible to predict the next result.

The mechanics of the seed and the perpetual cycle

RNG on an online slot machine (slots) operates perpetually. The software never stops.

• Continuous cycle: Even when no one is playing, the microprocessor generates thousands of number sequences per second. This is why it is said to be perpetual.
• Moment T: When you click on ‘Play’, the software freezes the precise moment (to the nearest millisecond) and selects the number generated at that moment.
• Translation: This number is converted into a visual result via a mapping table. For example, the number 4,294,967,296 will correspond to a stop on ‘Three Cherries’.

When you click with your mouse, the result (win or loss) is determined by the RNG; the animation of the spinning reels is purely aesthetic.

The law of chance: Audits and Certifications

Trust is an operator’s most valuable currency. To prove that their RNG is not rigged, casinos and game providers must submit their source code to independent auditing agencies.

These organisations perform rigorous statistical tests, such as the famous Diehard tests, to ensure that the results do not follow any detectable pattern.

These audits are the only guarantee that the mathematical code has not been altered in favour of the house beyond the normal mathematical advantage. They therefore provide a guarantee of fairness for players.

Organisme	Main role	Reputation
eCOGRA	Software auditing and player protection	Industry gold standard (based in London)
iTech Labs	RNG certification and RTP calculation	Very common in Australian and European casinos
GLI	Technical testing and regulatory compliance	World leader, very strict

What is the difference between RNG and RTP?

Don’t confuse randomness (RNG) with generosity (RTP). The RNG ensures that the mix is random, but the RTP (Return to Player) determines how much the game pays back to players in the long run.

Imagine a bag of marbles:

• RNG ensures that you pick the marbles blindly, without cheating.
• RTP determines how many red marbles (winners) and black marbles (losers) are put in the bag at the start.

A game can have a perfectly fair RNG (certified by eCOGRA) but a very low RTP, which makes winning more difficult. Technical fairness does not guarantee profitability for the player, it only guarantees the absence of manipulation.

Some myths surrounding RNG

Few players really understand RNG, which fuels the most persistent urban legends on player forums. It is time to set the record straight with the technical reality.

Myth 1: The win is bound to come

RNG has no memory. Each draw is an independent event. Whether a machine hasn’t paid out a jackpot in a month or just paid one out five minutes ago, the probability of winning on the next spin remains exactly the same. The concept of a hot or cold machine is a cognitive illusion (the gambler’s fallacy).

Myth 2: The casino changes the RNG at the weekend

Changing the RNG or RTP (Return to Player) of a certified game is a complex process that often requires re-validation by regulatory authorities. It’s not just a matter of flipping a switch in an office on Friday evening to lower the payouts.

Myth 3: Playing faster changes the outcome

Whether you use the Turbo Spin option or wait 10 seconds between each spin, it does not change your odds. You simply intercept a different value in the continuous stream of the RNG, but that value remains random.