RNG Guide: How Casino Outcomes Work

RNG Guide: How Casino Outcomes Work

8 min

The RNG may be a mystery to newer players. So we applied ourselves to the matter and created this handy guide for those who want to know whether a casino is fair and just how random a Random Number Generator can be. There is a variety of games to check out, all programmed with RNG. Since it affects your playing outcomes, we analysed how this microprocessor works on a significant range of games.

What defines a Random Number Generator? What’s an RNG?

RNG or Random Number Generator refers to a program determining what symbols and cards you will get when wagering on slots and card games. Naturally, live dealer titles do not operate with such technologies.

Can you predict its pick of symbols and jackpots?

Theoretically, yes, but practically, it is impossible for the player. There are two categories of this generator, and neither of them allows for quick prediction.

The two RNG types


Without further ado, the two categories in aleatory number generation are:

PRNG (Pseudorandom Number Generators)

These are the ones which randomise sequences up to a point. Then, the elements will start repeating. Even though this makes it apparently predictable, it takes remarkably long for repetition to occur. Most online casinos use it.

HRNG (Hard Random Number Generator)

This type ensures entirely random sequencing, and the possibilities are infinite. Most people in the tech and entertainment industries avoid it since it is famously difficult to manage.

Can you trust a Pseudo Number Generator?

Even though it does not contain fully arbitrary sequences, it will take a remarkably long time before the numbers start repeating. In fact, although the combinations are not endless, they tend to reach infinity.

Why are pseudo generators popular?

The reason why developers choose these pseudo versions of RNGs is their accessibility. They are much more comfortable to manage than hard number generators. Informaticians have tried to develop randomisers since the late ‘40s. Alan Turing was the first to create a calculator that generated random lines, an HRNG. Later, scientists focused on the easier-to-manage PRNGs.

How does RNG work on slots

Did you know that 70% of all gambling sites’ income comes from slot plays?

Slots are the most frequent pick of UK gamblers. Thus, we created a step-by-step guide to show you how this system works on them and how this can influence your gameplay. Land-based slots also employ Random Number Generators, but since they are physical machines, they are more susceptible to rigging. Improvements in programming make online slots go through the possible spins more times, which translates to enhanced security.

The system adapts to your playstyle

The bottom line is that your gameplay does not need to change to accommodate the generator.

Playing according to a betting strategy will also not help change the outcome – knowing that a website employs RNGs is simply the way to see that you are safe while playing, and all results come from fair gaming.

The hit frequency’s role

This value refers to the rate at which you may land a positive combination. This way, you can appreciate how much of the funds you staked may return to you over time.

This hit frequency differs according to the game type: for slots is lower, while for table games is higher. Knowing a slot’s hit frequency will let you know your virtual chances of gaining turnover.

It is not clear-cut and still not a way to predict your outcomes. Scoring a jackpot has a 27000 to 1 probability, and the everchanging numbers make it almost impossible to land the pot.

Games with higher frequencies will often dish out smaller payouts; jackpots are more likely when you play spins on low hit frequency titles. Remember that the rate will drop significantly on a progressive jackpot slot.

Is there a tie between RTPs and RNGs?

There is no actual tie between these two, but gaming organisations will generally test both when applying their expertise.

How does RTP & RNG testing go?

After trying a game’s randomiser, the testers will also check its return to player rate, or RTP, for short.

Although each game provider chooses the RTP for its products, the institutions must check the integrity of this value.

Card games and live dealer games

Software-based table options also operate on random generators. Whether you prefer playing on UK online Blackjack casino sites, UK Roulette sites, Video Poker pages, or other kind of casinos, what matters the most is whether they are software-based or live dealer products.

RNG is not universal in online casinos!

Naturally, live dealer products have no such system.

Instead, they have the croupier use multiple decks to randomise the gambling outcomes.

Fairness is still checked and ensured

Even so, software providers for live casino options like Evolution Gaming respond to the same authorities, and their sessions do receive testing for fairness.

Although these sessions are different, and none of them is superior, software tables come with more regulations, while live dealer games win in the brick-and-mortar-feel department.

Are RNGs rigged?

Rigging is out of the question. When a casino operator wants to make his business legitimate, he must obtain certifications from game testing authorities. They may go for a Random Number Generator certificate or invest in a more encompassing eCOGRA, GLI, or TST approval.

How to check that a casino uses RNG

Please note that such information must be public!


Checking a casino’s footer is your best option

When you scroll down, you will be able to see core information about the website, including:

  • The managing company’s name, along with its serial number and physical address;
  • The authority licencing it, including the licence number and registration date;
  • The certificate it has (an eCOGRA/GLI/TST/Verisign is preferable to an RNG one);
  • An RTP page (if not available in the footer, each game’s paytable must display it);
  • The casino’s Alternative Dispute Resolution or the way in which they manage casino disputes.

How to obtain certification

The operator must contact a testing authority or a lawyer who will do so on his behalf. If he asks for an RNG certificate, a testing authority will verify the platform and its games. However, an eCOGRA, GLI, Verisign, or TST certificate is even more valuable – it contains additional, more thorough tests. Furthermore, all these authorities operate in the United Kingdom, complying with the UKGC’s terms.

Certification is an intricate process, at the end of which you may be sure that the casino you’re browsing is safe.

Once an operator receives his documentation, he must publish it on the casino page. Otherwise, he risks fines, and the authorities can take legal action against him. If you do not see this information, especially the RNG-related one, check the website’s Terms and Conditions page. If there is no info there either, we advise you to leave the casino and head to a more secure gambling page.

Can RNGs be predicted?

Top online casinos UK go through testing before establishing a type of RNG. And there are numerous authorities regulating gambling sites’ activities. There’s no real possibility of prediction.

This is not the only value that gets better in online gaming

The most reliable indicator of your outcome, the Return to Player, is also higher than what you’ll find in brick-and-mortar locations.

Why does that matter?

Because you get a clear picture of how the house edge will affect you in the long run, maintaining a land-based casino costs more than a web version, so the payout gap tends to be higher. And like RNGs, transparent RTPs result from a fully licenced and secure online casino. Checking out our website will ensure that you only find legitimate gambling businesses, which operate on RNGs.

Are RNGs really random?


Random number generators are ‘acceptably random’, to cite the UKGC.

Many other authorities in the field evaluate the casino businesses’ algorithms and overall fairness before applying their seal of approval. So, players must not be able to predict the outcome. The system must be intricate enough for third-party software not to guess the following sequence of numbers and symbols.

A predictable system might not only create room for irregular play, but it also casts a shadow of doubt over the casino’s legitimacy. If such a situation arises, the UK Gambling Commission may fine the offending party and even revoke its licence.

How do you beat an RNG?

To be more specific, the level of randomness is too high even for a machine to process.

As such, it would be impossible to collude with casino play even if you had technology on your side. Especially on slots, the gameplay is left up to chance. Despite its often-masterful coding, an RNG can crash and this is an important flaw you must remember.

If something like this happens, the UKGC imposes clear regulations

Firstly, operators must report any game whose coding allows excessive winnings or losses beyond or below the designated RTP. Even if they do not have much information on the error, reports are mandatory.

Then, the respective games must be taken down temporarily

Punters should have no more access to a title with a faulty design. The game might go back on the website only after the casino and game testing authorities have finished their investigations.

The unfair results are paid back

The regulatory body UKGC will also ask the operator to determine each player’s excess or insufficient funds affected by the error. As such, you will get your actual payouts at the end of these investigations, whether higher or lower than your erroneous turnover.

If you notice that a defective product is still available to play, you may raise the issue with the customer support team. If the result is not satisfactory, you have the option to escalate the complaint to the website’s assigned ADR or report the issue to the UKGC directly. Filling the request form is accessible, and the waiting time will also be on your side; the best reason to contact it, however, is that you’ll receive an objective verdict on your situation.

Final remarks on this software

For a fair gaming experience, RNGs are essential. These algorithms will ensure that you receive a fair outcome – even though the house does famously have an edge, it cannot widen it by ‘rigging’ its available products.

Authorities advocate for it

Authorities like eCOGRA, TST, and GLI make sure of it, as does the strictest commission in the field – the UKGC. Always check the websites’ footers and T&Cs pages to find these institutions’ seals of approval. Although the sequences will generally not repeat infinitely, the randomness factor is high enough for repetition to take nearly an eternity to occur.


When creating this casino guide, we checked multiple sources. We consulted:

  • Legal pages
  • Gambling Commission’s platform
  • Other institutions which ensure the games’ safety

Other resources that we’ve used

To contextualise RNG, we also accessed articles on the history of science and did our best to present the information clearly and concisely. Our guide is a means to popularise this concept, which is prevalent in iGaming and other e-products. We saw where you can find RNG-related information and what seals of approval to search by entering and reviewing multiple casino websites.

Tudor Turiceanu
AuthorTudor TuriceanuCEO & Chief Editor at CasinoAlpha

Tudor Turiceanu uses his multiple systematic skillsets to oversee and coordinate the CasinoAlpha project. He assists the authors in creating a transparent gambling niche for users. As a CEO and Chief Editor with broad knowledge, Tudor knows the importance of transmitting confident advice.