What Is a Random Number Generator?
A random number generator is a system that produces numbers with no predictable pattern. In pokies, it is used to make sure every outcome is down to chance, with no way for a player, venue or casino to predict or influence the next result.
There are two main types:
- Pseudorandom number generators (PRNGs) use a mathematical formula to produce a long sequence of numbers that behave randomly for all practical purposes. Almost all slot games use this type of RNG.
- Hardware random number generators draw randomness from unpredictable physical processes, such as electronic noise. They are sometimes used to provide the starting value, or seed, for a PRNG.
How a Pseudorandom Number Generator Works
A PRNG starts with a value called a seed. It applies a mathematical formula to the seed to produce a number, then applies the formula again to that result, and so on, producing a very long sequence of numbers.
Although the formula is fixed, a well-designed PRNG has three important properties:
- Unpredictability: without knowing the internal state of the generator, the next number cannot be predicted from the numbers that came before.
- Even distribution: over time, every possible value appears with the expected frequency, with no bias towards particular numbers.
- A very long cycle: the sequence is so long that it does not repeat in any way that could be noticed or exploited.
In pokies, the RNG runs continuously, generating numbers even when no one is playing. Because numbers are produced so quickly, the exact number used for your spin depends on the precise moment you press the button, which no person can control.
From a Random Number to a Result on the Reels
The RNG produces raw numbers, often across a very large range. The game then converts, or scales, each number to fit the outcomes it needs.
Example: A reel has 64 possible stopping positions. The game takes a random number and converts it to a value between 1 and 64. That value tells the game where the reel stops. The process is repeated for each reel, or a single number is used to decide the whole result, depending on the game's design.
The probability of each symbol landing depends on how many positions it occupies on the reel, which is set by the game's designers. This is known as symbol weighting and is explained in our guide on how slot machines work. The RNG makes the selection random. The game's maths decides what each possible selection pays.
Features such as free spins triggers, wild symbols, multipliers and bonus prizes are decided in the same way, using further random numbers.
Why Every Spin Is Independent
A pokie's RNG has no memory of previous results and no knowledge of how much you have won or lost. Each spin uses a fresh random number, so:
- A long losing run does not make a win more likely on the next spin.
- A big win does not make the next spin less likely to win.
- A machine cannot be "hot" or "cold" in any way that predicts future results.
Believing that past results affect future ones is known as the gambler's fallacy. It is one of the most common misunderstandings about pokies. Our Pokies Myths Explained guide covers it in more detail.
Independence also explains why your short-term results can be very different from a game's RTP. The RTP is a long-term average across millions of independent spins, not a target the game tries to reach. See RTP vs Actual Slot Results.
What You Cannot Influence
Because the result is decided by the RNG the moment you press spin:
- Stopping the reels early only ends the animation. It does not change the result.
- Spinning faster or slower makes no difference.
- Autoplay and manual spins produce results in exactly the same way.
- Changing your bet size changes how much you win or lose, not the random selection itself, unless the game rules state that bet size affects a specific feature, such as jackpot eligibility.
How RNGs Are Tested and Certified
RNGs are tested to confirm that results are genuinely unpredictable and that the game pays out in line with its published maths.
Independent Testing Laboratories
Specialist testing laboratories examine a game's RNG and maths before it is released in regulated markets. Their work typically includes:
- Statistical testing of very large samples of generated numbers to check for patterns, bias or repetition
- Source code review to confirm the RNG is implemented correctly and cannot be manipulated
- Maths verification to confirm that the game's RTP and payouts match the published figures
- Ongoing checks when games or systems are updated
Regulation in Australia
Pokies in Australian venues must be approved by state or territory regulators before they can be installed. In New South Wales, for example, a new or modified gaming machine must be tested by a licensed testing facility before it can be approved. Queensland publishes minimum technical requirements for random number generators used in gaming equipment. Machines must also meet the Gaming Machine National Standard and local technical requirements.
Online Slots
Online slot developers usually have their games tested for each market in which they are licensed, and many publish certification information on their websites. Online, the RNG usually runs on the game provider's servers rather than on your device. Our Slot Game Providers section notes the licensing and testing information each studio makes available.
What Is "Provably Fair"?
Some crypto casinos offer "provably fair" games, mainly their own in-house games rather than slots from major studios. These games use cryptography so that players can check that a result was not changed after a bet was placed.
In simple terms, the casino commits to a hidden value, called a server seed, by publishing a scrambled version of it, known as a hash, before you bet. Your own value, called a client seed, and a counter, called a nonce, are combined with it to produce the result. After the server seed is revealed, you can check that it matches the hash and recalculate the result yourself.
Provably fair systems can show that an individual result was not altered. They do not change the house edge or make a game more generous, so the game's RTP still matters.
Can an RNG Be Rigged?
In regulated markets, RNGs and game maths are tested and approved before release, and changes generally require further testing or approval. This is designed to stop operators from manipulating results.
Outside regulated markets, protections can be weaker. Games from well-known developers are usually the same certified versions used elsewhere, but players have fewer ways to resolve disputes with unlicensed operators. In Australia, it is illegal for companies to offer online casino games, including online pokies, to people in Australia under the Interactive Gambling Act 2001. Our How We Review page explains how we assess licensing and fairness in our casino reviews.
Playing Responsibly
Knowing that every spin is random is one of the best protections against chasing losses. No pattern, system or feeling can predict the next result. Set a budget and time limit before you play, and stop when you reach them.
Our guides on setting gambling limits and recognising gambling harm explain practical steps, and Gambling Help Online offers free, confidential support 24/7 on 1800 858 858.