Random number generators

You can’t tell the symbols that will appear on the next slot machine spin. Similarly, you can predict where the next dice roll on a roulette wheel will end. Random number generators (RNGs) are the gold standard to get unpredictable results and ensure that casino games are fair.

Online casinos use random number generators for all their games, just as developers do. That covers slot machines, dice games, card games, and other table games. These generators generate random numbers to satisfy regulations and our need for complete fairness.

Random number generators do not apply to the blackjack or baccarat games in land-based casinos. However, they apply to physical slot machines to ensure randomness as you slot in your coins to play. Let’s see how RNGs work, the prominent testing agencies, and why you should play online at random number generator casino sites.

By Adiela de Bruyn - Updated 2024/02/08 - Estimated reading time: 8 minutes.

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Random number generators
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Aspects that control the gameplay of online casino games

Casino operators do not control the gameplay or payout of the casino games. They wait at the finish line and pay your winnings, depending on the game’s payout percentage.

Online casino games vary in the odds they offer. Your winning chances vary from one slot game to another. The same thing applies to dice and card games.

Variance and the return-to-player rate affect gameplay and your winnings. These parameters are more prominent in slot games. You might hear of the house edge in other casino games, like roulette, blackjack, and other table games.


Slot machines have variance, also called volatility. It refers to how often you will hit a winning combination when playing slot titles. Having five reels or more does not mean the game will have a higher variance.

Slots cycle between the low, medium, and high variances. Some offer volatility that adjusts from medium to high or from low to medium. Even so, some games have adjustable variances, and you can pick which level you want while playing.

The variance level reveals the win frequency and the risks. These parameters build on RNGs and their randomness. Therefore, the table below compares typical volatilities in slots and their win frequencies:

VarianceWin FrequencyRisk
HighLowHigh risk with high reward
MediumAverageAverage risk with moderate rewards
LowHighLow risks with low-paying wins

The RTP and pay tables

Online casinos do not impose their preferred player payout percentages on the games (slots, table games, live dealer games, etc.). Instead, they respect the values the game developers offer.

RTPs do not apply to single-game rounds. Instead, they reveal how likely you’ll profit from playing the game regularly. The casino's software will always show you the game’s RTP.

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How RNGs Work

RNGs are computer programs that generate random numbers each second. These random numbers are independent, without any pattern. Also, the RNGs can provide a single random number or a series when needed.

For example, each click of the spin button on a slot machine causes the random number generator to produce random number combinations. The same thing happens when you hit the button for a roulette spin.

RNGs deal cards in virtual games through the random numbers generated. That ensures fair play on each round, as the casino cannot predict which cards you will receive from the random number generator. Hence, all casino software requires random number generators to provide fair games.

How an RNG Produces Numbers Randomly

Online gambling platforms host thousands of players, each clicking the play button, whether on a slot machine or a table game. Each click produces random numbers that generate unpredictable results.

Random number generators are not limited to online gambling platforms. We see them in computer simulations, statistical tests, security applications, etc.

You only need a basic understanding of how the random number generator produces random numbers. Hence, we leave the extensive process to the testing agencies.

Pseudo-random number generator (PRNG)

A pseudorandom number generator uses RNG algorithms to produce large number strings from a shorter number string (seed number). The seed number can come from a physical or natural source, like the true random number generator. That means the casino does not need external numbers for the algorithm to continue working.

Hackers can attempt to break the program code since pseudo-random number generators are digital. Moreover, there are a finite number of algorithms. However, this is highly unlikely. Online casinos must test their RNG software from time to time.

Most casinos use PRNGs on online casino games that don’t have live dealers. That includes slots, crash games, table titles, bingo, scratch cards, etc.

True Random Number Generator

These random number generators base their randomness on physical events. Hacking a hardware random number generator is impossible because we can’t control the physical events that produce the results.

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How Casinos Use Random Number Generators

An online random number generator can work as an automatic card shoe shuffler for playing cards or flipping coins. The software is always active on these casino games, ensuring randomness on each play.

Developers transform each random number into a game element. That includes the symbols in slots or cards in table games.

We can’t say beating a random number generator is impossible. A skilled hacker with the RNG algorithm can beat the RNG software. Notwithstanding, this occurrence is highly unlikely among regular casino players.

Randomness remains integral to the intrigue and fun of online casino games. You can work out the probability of what’s likely to happen, like on a roulette table. This randomness ensures all players have fair play.

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Proving the Fairness of a Random Number Generator

Casinos use one central random number generator that software providers plug their games into. Hence, one RGN controls the symbols on all the slots and the cards in all card games.

This system places a huge demand on the casino sites to ensure fair RGN games. Regulators demand independent testing before verifying a casino’s RNG. These tests must be done regularly as the casino adds new games and expands its gambling services.

Regulators, like the UK Gambling Commission, can test a casino’s RNG. However, independent testing agencies are more prominent in testing the casino system. These third-party testing agencies do the following for gambling platforms:

  • Algorithm evaluations
  • Game and mathematics evaluations
  • Ongoing game payout verification and live dealer reporting
  • Poker system audits
  • Full security audits

eCommerce Online Gaming Regulation (eCOGRA)

This London-based testing agency was launched in 2003. It is a standards organization in online gambling and does the following:

  • Certify and regulate online gambling operators
  • Ensure operators meet strict guidelines for player protection, fair play, and responsible gambling.
  • Inspect and certify online gaming software
  • Audit information security management systems

Casinos with the eCOGRA seal communicate credibility and an assurance of good value for money. You’ll find the seal at the footer, among the casino’s licenses.

eCOGRA’s presence does not take away the need for casinos to be licensed. The latter ensures you play on a gambling platform the law approves of.

Gaming Labs International

This independent testing agency has been in operation for 35 years, building a reputation for trust and credibility. Its services in the gambling industry cover gaming regulators, game providers, and operators in over 560 global jurisdictions.

  • Gaming Labs International offers audits, consultations, field inspections, risk and compliance, project management, etc. It also awards the ISO 27001 information security audit and certification.

Technical Systems Testing (TST)

Player protection is at the forefront of TST’s services. This third-party testing organization ensures online casino games have sufficient quality and fairness. It is a leading auditor for South African online casinos, auditing, analysing, and accrediting them.

  • Casinos seeking TST’s accreditation must prove that their RNG algorithms are fair. The testing agency also liaises with game developers to create titles that are fair from the beginning.
  • TST uses the Total Gaming Transaction Review (TGTR) to monitor inputs and outputs from a casino’s RNG software. This process helps it to verify payout percentage claims, check completed transactions, and conduct spot checks. Then, it uses this information, combines it with other analysis, and determines the casino’s randomness.
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Casinos should provide good value for money through unbiased games and payouts. They use RNG programs to achieve truly random results, except where live dealers are involved. Licensing bodies check the casino’s software and analyze it for any manipulations.

RNG programs are unbiased, but casinos can manipulate them to skew results in their favour. Hence, we recommend playing on sites with accreditations or certifications from reputable independent testing agencies.

Technical Systems Testing does an excellent job of auditing and analysing RNG programs. However, it is less popular in the global industry. You can look for other big names like iTech Labs, eCOGRA, and GLI on the casino’s page.

Stick to sites with fairness certifications and verified payouts. Notwithstanding, play with responsible gambling tools.

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Frequently Asked Questions About RNG (Random Number Generator)

Can a casino’s RNG be hacked?

Yes, but that requires accessing the RNG algorithm. Hacks are less likely to occur on credible gaming sites.

Will I lose money for playing on a site without a certified RNG?

Sites without a certified RNG are not entirely bad and out to rip players off. However, the absence of a certified RNG is a red flag. You are better off not playing on them.

How do I find a casino’s RNG certificate?

Sites with an accredited RNG proudly display the certifying body’s seal on their homepage. You can also check the legal or “about us” page to see the RNG certificate.

Author: Adiela de Bruyn

Adiela de Bruyn

Adiela de Bruyn, our founder, launched this site in 2016. Since then, she's written over 100 pages filled with crucial info to enhance your gaming experience. Her goal? To provide you with the best, most reliable online casino knowledge.

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Article published 2020/10/17