How to Properly Test Random Number Generation

test random number generation

When you spin the reels on slot machines at a land-based casino, you have to wait a bit to know which symbols will land when the spin ends. If you’re also playing blackjack or online poker at a physical casino with a deck of 52 cards, the dealer shuffles the deck, and the cards are dealt to you and your opponents. Due to this randomness, nobody knows what cards the others have.

To ensure randomness remains in modern casinos, iGaming sites use random number generator (RNG) software to spin reels or shuffle cards. The online games generate random numbers to ensure nobody can influence, rig or tamper with gaming outcomes. This guide explains how RNG works in online casinos and how to properly test it.

What is a random number generator?

A random number generator (RNG) is software used by casinos to offer players provably fair games. The software generates random gaming outputs to guarantee transparency and fairness in your favorite casino games, including online slots, blackjack, poker and roulette.

After wagering at online gambling sites, the RNG software displays the results of the game’s outcome, so you know whether you won or lost. The RNG achieves this using a software algorithm. Its production of random numbers prevents the casino from rigging its games and prevents players from predicting gaming outcomes.

How does RNG work in online casinos?

Virtually all online casinos, including the best online poker sites, use RNG software to ensure the fairness of games. The system is a crucial part of their compliance with regulatory laws that strive to protect players from rigged games. Today, you can find provably fair games at online casinos thanks to the RNG systems that are in place.

Many types of RNG exist, but the two most popular options at casinos are the True Random Number Generator (TRNG) and the Pseudo Random Number Generator (PRNG). Both RNG variants generate random numbers using algorithms; however, they work differently.

TRNGs use hardware tools and unpredictable physical conditions such as air temperature, thermal noise and clock movements to generate random numbers. Typically, they have a measuring device that collects and interprets the values of the environmental conditions, so their results are more reliable. However, hardware random number generators are expensive, so they are rarely used.

Conversely, PRNGs are completely computer-based. Instead of external factors, they rely on the use of algorithms alone to produce random numbers. Typically, the algorithm uses a seed number to produce random results, which allows it to produce a new sequence of random numbers every time a game is played.

The drawback to the PRNG algorithm is that it’s fixed. At some point, the initial seed number can be repeated for the cycle to reset. This is why it is not truly random. Instead, it uses its seed number to provide an element of randomness, which is why it’s called a pseudorandom number generator.

Despite this, PRNG is the most used RNG system at online casinos. The algorithm is present in virtual games that don’t have actual human dealers or human input. To solve the issue of potential repeated outcomes, the RNG is constantly running, even when games are not in use.

When you open an online casino game and press “Spin” or “Deal,” the RNG is already producing a new seed. It does this every millisecond, ensuring fair outcomes.

Which casino games use random number generation?

All video casino games use RNG to determine their outcomes. The system guarantees players that a casino’s gaming result is truly fair, and that players have the opportunity to win. Common casino games using RNG include:

  • Online slot machines
  • Video poker
  • Craps
  • Table games
  • Scratch cards
  • Keno

Each game may use the RNG system in a unique way. For instance, when playing a card game, the RNG determines the order of cards in the virtual deck by constantly shuffling the cards. In slots, the RNG is active the moment you press the “Spin” button. The system arrives at different symbol combinations from one spin to another, which is why you may instantly hit a jackpot or spin multiple times without a win.

How to test online casino RNGs

You can test a casino’s RNG to ensure the game isn’t rigged against you. Checking which tests and reviews individual sites is a good place to start. However, to better understand how this process works, below are some of the most effective ways that casino RNG testing is performed:

Checking independent licensing sites

Reputable online casinos typically undergo RNG testing and audits every year to renew their fairness certificates. The easiest way to verify an operator’s RNG system is to visit its auditor’s or licensor’s website and see if the casino’s license is still active. Popular licensors include eCOGRA, iTechLabs and GLI.

Using testing software

If you prefer to test a casino’s fairness yourself, you’ll find various RNG testing tools on the market. These tools use programming languages such as Python to evaluate and analyze data to assess an operator’s fairness and ensure its result system is truly random. Some popular RNG testing tools include TestU01, the National Institute of Standards and Technology (NIST) Statistical Test Suite and DIEHARD Tests.

You can also use tools to perform various statistical tests to assess the randomness of an online casino. These include:

  • Frequency or Monobit test
  • Poker test
  • Block frequency test

These tests ensure the binary numbers (1s and 0s) in a result are the same, check the pattern distribution and check the frequency of the same result in a sequence.

Can you beat RNGs at online casinos?

Simply put, it’s impossible to defeat a casino’s RNG system to guarantee wins. Sophisticated, automated algorithms are used to ensure you cannot interfere with or manipulate the gaming results. What you can control is the online casino you choose to gamble at.

It’s crucial to note that RNGs do not stop you from winning at casinos. They only ensure fair play.


Online casinos have random number generators in place to ensure a safe and fair gaming experience. Most online gaming sites have RNG certification, but you can test their effectiveness using the methods above.

Ultimately, it is crucial to play at only reputable US online casinos with RNG certification to avoid games with easily manipulated outcomes.

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