About Random Number Generators

Have you ever read or heard someone say that online gambling is perfectly legit because all games are random?

Yeah, well, they’re wrong. The games are not random.

Don’t get us wrong. We’re not saying the games aren’t fair or that casinos are stacking the game. They aren’t – most of them anyway. However, most people don’t know anything about random number generators (RNGs).

We don’t blame them though. It is quite a complex and technical subject. And that’s not a rabbit hole that most people like to go down. Neither do we, so let’s tackle this topic from the surface instead. Just the basics.

What do you think?

Then let’s get into it. Below we answer the most frequently asked questions about RNGs.

What is a Random Number Generator?

It’s a computer programme that (seemingly) randomly spits out results.

There are different types of RNGs. The ones that casinos use are called pseudo-random number generators. What makes these unique is that they don’t require any external input (numbers or data) to produce an output. All they need is an algorithm and a starting number.

New seed numbers (and results) are produced every millisecond. This is done simply by taking the last number or two numbers produced and then using a math operation (addition, subtraction, multiplication, division, etc.) to create a new ‘random’ outcome.

Then rinse and repeat.

But because there is nothing arbitrary about math operations – ie 1+1 always equals 2 – any given input will always produce the same output. Therefore, RNGs are not really random.

It’s also why RNGs are hackable. Algorithms (and their operations) are fixed.

And there are only so many known algorithms in the world. If someone knew what algorithm(s) and number(s) casinos were using, they could use that information to steal millions of dollars from the casinos.

We’ll show you an example of someone who did just that later.

How do casinos use RNGs?

They are used for virtual games, which are games where there is no dealer.

You would think that this is especially true for online casinos. But offline casinos also use them for their virtual blackjack and roulette games, as well as keno, video poker and video slot machines.

Let’s take slots for example. How exactly does an RNG work?

The general idea is this:

They assign a value to each symbol on a reel. And let’s say there are 12 symbols per reel, and this is a 5 reel slot machine.

The RNG would come up with a value of 1-12 for each of the 5 reels. The result would be 5 different symbols.

And if those 5 “random” symbols form a winning combination, you will be paid according to the chart.

Can you cheat RNGs?

In theory yes. But most people are unable to do it.

There are of course exceptions.

One (online) incident was discovered in 2008. A man, Norman Clem, was playing craps at World Wide Wagering. But he got the feeling that he was losing a little too much. So he decided to track his gains/losses over the course of a year.

Norman made 3200 pass and don’t pass line bets, which should win about 49% of the time. But he didn’t. He won just 856 times – or 27% – which is too far from the standard deviation. So he decided to post his results online.

Michael Shackleford, the man who built WizardOfOdds.com, ran his own test and found that BLR Software manipulated their games to increase the house edge.


This is, of course, a rare example. Most casinos we know (and we’ve reviewed for years) don’t do this. There is simply more money to be made in the long run by being honest.

In addition, the software of most casinos is tested by third parties. They would never get away with rigging their RNG anyway.

We’ll talk more about testing in a moment. But let’s look at another example of someone manipulating a random number generator.

His name was Ronald Harris. And he was a computer programmer who worked for the Nevada Gaming Control Board in the 1990s.

His job was to find flaws and errors in the software used for automated casino games.

And apparently, the temptation was too great.

He used his knowledge to modify certain slot machines so that they would pay out large sums of money when a certain series hit and a certain number of coins were entered.

Harris and his partner stole thousands of dollars undetected from casinos in Vegas between 1993 and 1995.

But then Harris went a little too far.

Towards the end of his run, he shifted his focus from slots to keno. He developed a programme that would determine the numbers that the game’s RNG would select in advance.

But the authorities soon figured it out. When Harris’ partner tried to cash in on a winning ticket, casino managers called investigators. Harris was discovered and arrested. He was sentenced to seven years in prison, but only served two.

He currently lives in Las Vegas. He is listed in the Nevada Gaming Control Board’s black book and is prohibited from entering a casino.

So assuming people don’t interfere with the programs, RNGs should be fair  .

But how do we know for sure?

What steps are taken to ensure that random number generators are fair?

All reputable (licensed and regulated) casinos are tested. At least their software is. This is done by independent third parties.

One such company is Technical Systems Testing (TST), a company now owned/operated by Gaming Laboratories International (GLI).

They offer a full range of testing and advice to both online and land-based casinos and gambling companies.

They perform all kinds of services and test evaluations, such as:

  • Random Number Generator (RNG) Evaluations
  • Game and Math Evaluations
  • Continuous verification and reporting of RNG or game payouts
  • Live dealer, sportsbook or betting exchange evaluations
  • Evaluations of lotteries and pari-mutuel system
  • Poker System Audits
  • Penetration testing and full security audits

Those who pass are given a small badge and certificate stating that their games are “fair”, meaning they are “random”.

That means their games are not affected by outside variables such as the amount of credits in the game, the size of the (potential) payout, VIP cards, and so on.

It also means that the machines meet minimum payout percentages set by federal and/or local authorities and gaming commissions.

For example, some states, such as New Jersey, only require their games to refund 83% of all money. But others, such as Nevada, must pay a minimum of 75% back.

These rules are different depending on where you play.

And each individual machine will never change. Not without going through an extensive process in any case.

For example, if a casino in Nevada wants to make changes, it must first notify the state. Then they would have to use state-approved chips, which have a paper trail. Then inspectors (randomly) check the machines for compliance.

All this to ensure that the games are fair and stay that way.


Well, that’s the Random Number Generator (RNG) in a nutshell. They are complex programmes that make casino games as random as programmes can be. And it will remain that way as long as they are tested and not harassed by rogue people.

RNGs are everywhere you look, not just in casinos. You don’t have to look beyond your smartphone or tablet to find out.

In April 2016, the TSA even started using a randomizer app at 100 different airports. All it does is pick left or right at random by using an RNG to tell each person which security line to go through.

It’s really no different from a casino RNG. Well, except maybe the experience.

After all, you will no doubt have more fun using a casino RNG than an airport security line.