A Beginner's Guide To Random Number Generators

A Beginner's Guide To Random Number Generators

The online casino industry, like many others, is always looking to get ahead by developing new technologies for its customers.

One of these sophisticated pieces of technology is the random number generator, or RNG, which helps to make iGaming more exciting for us, and more efficient for casino operators.

What is an RNG?

An RNG uses a complex algorithm, known as an MD5, to generate results for games which could have many different possible outcomes, for example, online slots. There are two basic types of RNG: 

  • The ‘Hardware Random Number Generator’ and the 
  • Pseudorandom Number Generator.

Both make sure that the computer generates completely ‘random’ results, but they work differently.

How the Hardware Random Number Generator (HRNG) works 

You’re more likely to find the HRNG in a land-based casino rather than an online one. This is because they're not as sophisticated as Pseudorandom Number Generators, but they're still effective.

The HRNG is an external device, which may be attached to a casino server’s USB port. It helps to generate completely random numbers using compound values as a starting point.

These numbers are generated by a rule or an action, so the algorithm produces results based on these ‘core numbers’.

This means that no HRNG is truly random. It relies upon an external output like a starting point on a roulette wheel, which is why online casinos tend to favour the more complex Pseudorandom Number Generators.

How the Pseudorandom Number Generator (PNG) works 

PNGs are preferred by online casinos and for good reason! Unlike HRNGs, PNGs do not need an external output to help them generate outcomes. Instead, they rely on seed numbers, which are produced every millisecond.

Seed numbers are produced by taking the last one or two numbers and using one of the following mathematical equations to create an outcome:

  • Addition
  • Subtraction
  • Multiplication
  • Division

So, what we get is a result being generated by the constant calculations of the PNG. The algorithms are set by developers who will likely have created their own software algorithm, and the numbers used within them are huge – we’re talking thousands of digits!

This does, of course, mean that PNGs are also not, in fact, entirely random! They rely upon a limited amount of outcomes which can be created through these equations. 

However, the amount of outcomes that can be generated is almost infinitely high, and the result is always different. 

That being said, RNGs are not totally flawless. Because of these calculations, they can technically be hacked. If a player knew every algorithm and seed number that a casino used, then they could theoretically ‘cheat’ the system.

Thankfully, modern algorithms using MD5 largely protect against this.

How do RNGs work at online casinos?

RNGs can be used in many different games, for example with online slots, blackjack, roulette, video poker, keno and more. In any setting where there is no dealer, the complex technology can recreate the ‘random’ experience we would expect from a simple shuffle of the cards.

The numbers generated through RNGs do, of course, depend on the game being played. For example, there could be between one and 37 numbers for European Roulette, but one to 52 with blackjack.

Let’s use a real online casino game example.

Using RNGs in online slots

In an online slot game, a value is attached to each symbol on a reel. So, there might be 12 symbols on five reels.

The technology would create values, one to 12, for each individual reel, giving the result of five different symbols. Anybody who has a winning combination of these five symbols wins.  

Can RNGs be predicted?

Yes, players have tried to ‘cheat’ RNGs using predictions, but this is extremely difficult, but technically not impossible.

In 2008, a craps (game of dice) champion took notes on every win and loss he had and realised that he was only winning 27% of his games, far from the standard 49%. 

Alternatively, a more technologically-minded player might try to hack into a secure generator and used a ‘hacked’ algorithm. This actually happened in the 90s when computer programmer, Ronald Harris, used his knowledge to change payouts based on certain sequences.

Luckily, modern security systems are now able to flag this kind of interference, informing operators of suspicious activity.

Can I trust an RNG?

You certainly can – RNGs in an online casino must, by law, be regulated by appropriate gambling bodies in your region. This can affect their randomness, but it also guarantees that they are fair for all users. 

A legitimate casino will be able to provide details of their compliance with these regulations. Trustworthy online casino operators are tested by independent third-party companies such as Gaming Laboratories International, which also regulates land-based casinos.

Stories like the aforementioned craps champion may make players question the true randomness of the games they're playing, but any regulated operator will display a symbol to show compliance.  

For example, on Mr Play you can see the iTech labs RNG certificate badge in the footer.


Like any industry, the iGaming industry has welcomed new technologies to improve the quality of its service. Though historically, RNG has been subject to tampering, new developments mean it is one of the safest methods for delivering fair results in online casino games.

RNGs are constantly producing new results, even when the player is not playing the game, meaning that they can be guaranteed never to get the same result twice.

The calculations can allow for a huge amount of variables, from one to 37 values in roulette to multiple card decks.

Just remember – if you want to play an online game that’s truly random, look out for the certification on your chosen iGaming website. 

Happy gaming!

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