The Complete Guide to RNG in Online Casinos

The Complete Guide to RNG in Online Casinos

RNG stands for Random Number Generator, and it does exactly as the name suggests; it constantly produces random number sequences. Without random numbers, it would be impossible to make online gambling to happen, and each legit online casino uses it on a daily basis.

RNG is also a quite widespread tool among the scientific community (especially in cryptocurrencies) and business as well (mainly online). Hence, RNG’s use cases are not limited to the online gambling industry only.

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Why RNG is crucial for online gambling industry

Randomness is an inherent part of any gambling activity, and it must be ensured by casinos at any cost. Otherwise, there can be two types of consequences, both of which are devastating for gambling industry: either a player would be able to cheat a casino or a casino would be able to cheat their players.

In land-based casinos, Randomness is ensured by well-known tools, such as roulette wheels, shuffle machines and dice. Those are the simplest random number generators, though they get the job done perfectly well so there is no need to reinvent a wheel, and land-based casinos have not quit using them even in our modern days.

In online casinos (except for live games) there is no place for wheels, shuffle machines and dice for obvious reasons. On top of that, some video slots have become too complicated in terms of gaming mechanics so there is no way to ensure Randomness using old-school tools.

The good news was that scientists have been studying Randomness for their purposes and came up with solutions on how to generate random numbers at some point.

Two types of RNG

There are basically two solutions on how to generate random numbers:

  • True RNG (or sometimes is called Hardware RNG). This is a physical device that produces random numbers from physical processes which are constantly happening within this device (at the particle levels). Those processes are random by their nature, for example, thermal noise, and scientific community has taken advantage of it.

  • Pseudo RNG is an algorithm (like software, and not a physical device) which consists of some formulas. In order to be able to generate random numbers, Pseudo RNG must have “seed” value, which is a long sequence of some numbers (think of it as a core of Pseudo RNG). Based on this seed, random numbers will be produced.

Can we trust “Pseudo” random number generator?

In online casinos, in order to generate random numbers, only Pseudo RNG is used. Why? Because True RNG can not scale as online casino players are making millions of bets each minute, and for True RNG it would not be possible to handle so many requests (or it would be rather too slow and very little fun to play in as a result).

Many online casino players become sceptical when they hear the word “Pseudo”, but they definitely should not. Let me explain why. It is “Pseudo” only in comparison with “True” RNG, and these names exist only to stress out this difference, mostly for scientific purposes. It does not mean at all that results of Pseudo RNG can be predicted or manipulated.

It is true that in Pseudo RNG, seed sequence can be manipulated. It only allows to set different RTP levels in video slots, but the outcome of a particular spin is absolutely random and unpredictable, even by creators of Pseudo RNG.

Let’s talk about how exactly Pseudo RNG is implemented in online casinos.

How does Pseudo RNG work in online casino games

Phase 1. Seed sequence is set up. It is done by software provider of particular casino game. Manipulating seed sequence allows to set up RTP at desirable levels.

Phase 2. Pseudo RNG constantly produces a stream of random numbers based on seed sequence. Some algorithm (set of formulas) “extracts” random numbers from seed sequence. These formulas ensure that, let’s say, online slot has some RTP level in the long run (ensured by having a seed sequence), but short term results are random.

Phase 3. At the moment a player presses “spin”, “play” etc. button, an online casino game grabs random numbers that were in place at this particular moment.

Phase 4. Based on these random numbers, an online casino game displays results for a player (reels of online slot stop in a particular order, particular cards are dealt in Baccarat and Blackjack, a ball in Roulette lands in particular pocket).


The most common misunderstanding about RNG

I have heard so many times theories that a casino game, especially online, has “memory”, and it produces outcomes based on previous results. It is absolutely untrue, and it is not how Pseudo RNG works at all.

Online casinos do not need such tricks since all casino games are already designed to cause losses for players in the long run. In other words, a legit online casino does not care how much a particular player won in a particular slot during a particular gaming session. A casino will end up with long terms profit anyway.

How RNG affects some casino games

RNG affects online Blackjack in a big way making all counting strategies absolutely pointless. It is a predictable thing to happen because unlike its land-based counterpart, online Blackjack does not resort to physical decks of cards, and a player can not take advantage of it.

For the same reasons, in online casinos RNG makes impossible any other strategies that would be profitable in land-based casinos (for example, card counting in Blackjack).

However, RNG in online casinos does not affect such strategies that are not profitable for casino players, such as, Martingale etc. So you can continue to use them in online casinos if you would like to do so.

RNG in live online casino games

In live online casino games (with a live dealer and physical equipment), there is no reason to use Pseudo RNG, since Randomness can be easily achieved by old-fashioned tools (physical wheels, cards, dices). It follows that not all casino games that you can come across in online casinos have to resort to RNG.

Is it possible to cheat RNG?

In theory, the only way to cheat RNG is to have physical access to it. In the case with Pseudo RNG, it could be done by manipulating its seed sequence.

In practice, it is very expensive to perform such sort of attack on a casino’s software, since its crucial infrastructure, and it is closely guarded as a result.

Summing up, I would say that absolutely everything can be hacked. Discarding legal and moral aspects, the question is only how much it will cost. But don’t feel unsafe playing in online casinos since even if such attack is successful, it will make harm only to a hacked online casino. As for my experience, I can not recall any successful attack in the last few years.

How does RNG get tested

This is definitely an aspect that all online casino players should keep a close eye on.

I have the whole article devoted to this matter. Jumping forward, there are some third-party companies in charge of fairness tests, and they assess RNG.

They usually do it that way. Let’s say we are tossing a coin, and outcomes are supposed to be 50/50 in the long run. In order to verify that the game is not rigged, we would toss a coin 1,000,000 times and look at actual results. If they are 50/50 (or super close to it), then the game is fair.

Fairness testing companies do exactly the same. They make millions of spins in a particular online slot and compare actual results with theoretical.


I hope you have got a basic understanding how RNG works in online casinos, and, from now on, it will be impossible to make you believe in any superstition regarding online gambling since you have learnt the process behind the scenes by yourself.