When you spin the reels of an online slot or place a bet on digital roulette, how do you know the game isn’t rigged? Unlike a brick-and-mortar casino, you can’t see the dice being rolled or the cards being shuffled. Instead, trust lies in invisible algorithms known as Random Number Generators (RNGs) – this is what could easily be defined as the digital backbone of online gambling fairness. What does RNG actually mean? According to a NIST publication, it is “a process used to generate an unpredictable series of numbers. Also called a Random bit generator (RBG).”[1] – this is one of the ways to describe this technology, and it implies that there is no manipulation or anything that can influence the outcome to benefit anyone, which is exactly what we want in the gambling world.
RNGs, together with strict regulations and independent testing have as their main purpose to ensure that every spin, shuffle or roll is as unpredictable as possible – these systems are used everywhere in online slots games, but also modern slot machines also use microprocessors to run RNGs. That being said, getting here took decades of technological evolution, regulatory oversight and industry reforms.
So, in this article, we have now set out to explore how RNGs work, how they’ve evolved, the role of regulators and certification bodies plus other interesting things like a quick glance at what the future holds for fairness in online casinos.
The Early Days of Online Casino Fairness
Online casinos began appearing in the mid-1990s, when internet access became more widely available. If we want to name some of the first platforms, we have the title of InterCasino (launched in 1996 by Cryptologic) – “InterCasino is a client server application which allows users to connect from anywhere around the world, via the Internet, and gamble for real money. InterCasino is the first application of its kind.”[2] It is also worth mentioning the Gaming Club, which was launched by Microgaming around the same time; these platforms offered a small selection of digital slot machines and table games, and while Microgaming’s platform didn’t function fully online from the get-go (payments were still not done online until later than the launch of InterCasino), we can confidently say that these 2 absolutely paved the way for online gambling.
However, trust was a major issue – as anyone can probably guess already, RNGs at the time were not the same as today and they were much more basic as number generators, what we call a pseudorandom generator, which used simple algorithms to produce outcomes. While this was still mathematically serviceable, these early RNGs lacked the complexity and testing needed to assure true randomness and therefore complete fairness.
To add even more to the already existing problem, many early casinos operated without licensing or regulation – this is definitely to be expected in an industry that has just emerged and hasn’t been analyzed properly, but it doesn’t make the situation any better for those that wanted to gamble online at the time. It left room for scandals, with some operators accused of rigging outcomes or refusing to pay winnings. Stories of unfair practices spread quickly, damaging the industry’s reputation. Of course, we can hear similar stories even today, but now we have guidelines and we should generally be able to spot which casinos are not to be “touched”, by looking for information about their licensing, testing, gamble awareness resources and other things that hint at every platform adhering to rules and regulations in their jurisdictions or worldwide.
That being said, it was clear from the very beginning that for online gambling to survive, it needed to do its best to gain the trust of its potential clients, which could only be done by implementing better RNG technology and much more robust oversight – everything in its power to aim towards total fairness.
How RNGs Work in Modern Casinos
At the heart of every online casino game is an RNG. But how do these algorithms actually function?
Pseudo-RNGs vs True RNGs
Most casinos actually use Pseudo-Random Number Generators (PRNGs) – we mentioned these before as a “bad” technology to use, but the reality is that with the advancements that happened in the meantime, these generators are able to get very close to what is actually true randomness. “At their core, Random Number Generators are algorithms. They are sets of instructions or procedures designed to produce sequences of numbers that lack any predictable patterns. These algorithms use mathematical formulas to generate numbers that simulate randomness.”[3] While technically this is not “truly random”, the output is still unpredictable enough for gaming purposes, especially when combined with strong cryptographic methods (encryption of this type of data so that it cannot be exploited in any way).
Actual true RNGs (TRNG) are now being used in high-security environments, although some developers are experimenting with them for casino applications as well; these generators draw randomness from physical phenomena like atmospheric noise or quantum fluctuations. That being said, PRNGs remain the industry standard due to their efficiency and scalability.
| Type | Source of Randomness | Predictable? | Example Use |
| PRNG | Algorithm + Seed | Yes (theoretically) | Online casino software |
| TRNG | Physical noise (thermal, atmospheric, quantum) | No | Hardware RNG, seeding, cryptography |
| QRNG | Quantum-level measurements | Fundamentally unpredictable | High-security or scientific RNG |
To dive a bit further into understanding what True Random Number Generators do, we can say that TRNGs produce randomness by measuring unpredictable physical processes rather than using mathematical formulas like traditional PRNGs – so they draw data from physical sources capable of producing entropy (the natural randomness drawn from a system) such as electronic noise in circuits, atmospheric radio static, or quantum phenomena like photon behavior – these raw signals are then processed and they generate random bits, balanced 0s and 1s. “[…] random numbers are best obtained using physical (true) random number generators (TRNG), which operate by measuring a well-controlled and specially prepared physical process.”[4] We won’t dive any further into the quantum side of things, so this article doesn’t turn into a complete headache.
Application in Casino Games
| Game Type | RNG Application | Purpose of Randomness | Type of RNG Used | Additional Notes |
| Slots | Determines the final position of each reel on every spin. | Ensures each spin is completely independent, preventing patterns or manipulation. | PRNG (seeded by TRNG in some cases) | Each symbol combination is calculated in milliseconds before the reels stop, simulating a physical slot machine’s unpredictability. |
| Roulette | Selects a random number representing where the virtual ball lands. | Mimics the randomness of a physical wheel, guaranteeing fair outcomes for every spin. | PRNG | RNG-driven wheels allow for instant results and support features like auto-play and quick betting. |
| Blackjack | Randomly “shuffles” and deals cards from a virtual deck before each hand. | Prevents predictable card sequences and ensures fair gameplay for all players. | PRNG | Some games reshuffle the deck after every round to further eliminate predictability. |
| Poker (Video or Online Table) | Randomizes the dealing order and cards received by each player. | Keeps gameplay fair by removing any fixed patterns or dealer bias. | PRNG | In live-dealer hybrids, RNGs are sometimes used alongside physical cards for bonus or side features. |
| Craps / Dice Games | Generates random dice roll results. | Replicates the uncertainty of physical dice rolls. | PRNG | RNG-based dice systems are audited to match the statistical odds of real-world dice rolls. |
| Keno / Bingo | Randomly draws numbers from a virtual pool. | Ensures all numbers have equal chance of being selected. | PRNG or TRNG (in regulated draws) | Often verified by independent labs to meet lottery-grade randomness standards. |
| Instant Win / Scratch Games | Determines prize outcomes instantly at game start. | Guarantees each card or ticket is unique and unbiased. | PRNG | Uses pre-seeded RNG sequences to ensure fairness and transparency. |
What is also worth mentioning is that in gambling use applications, RNGs are paired with Return to Player (RTP) percentages and volatility models – this means while short-term outcomes are random, the game is still mathematically designed to hit certain payout ratios over the long run – just like in land-based casinos. This is part of how casinos the regulatory authorities have decided over time to transform the casino games in a way that seems the fairest to players. Speaking of which…
Regulatory Bodies and Certification Agencies
Modern online casinos don’t get to simply say “trust us”. RNGs are rigorously tested and certified by independent third parties.
Key Gambling Regulators
| Regulatory
Body |
Jurisdiction / Reach | Key Responsibilities | Reputation & Oversight Style | Notable Features |
| UK Gambling Commission (UKGC) | United Kingdom | Licenses and monitors all online and land-based gambling; mandates fairness, anti-money laundering (AML) compliance, and responsible gambling practices. | Extremely strict and consumer-focused; considered one of the toughest regulators globally. | Requires continuous RNG and game testing, regular audits, and transparent payout reporting. Heavy penalties for breaches. |
| Malta Gaming Authority (MGA) | European and international (especially EU markets) | Issues licenses to global operators, monitors compliance, and enforces anti-fraud and responsible gaming measures. | Balanced approach — robust but business-friendly. A major licensing hub for online casinos. | Offers several license classes (B2C, B2B), ensuring supplier-level compliance. Favored by major European operators. |
| Gibraltar Regulatory Authority | Gibraltar / international operators | Oversees remote gambling operations, focusing on fairness, player fund protection, and AML controls. | Highly reputable and stable; known for strong standards and fiscal advantages. | Frequently licenses large international casino and sportsbook brands. |
| Isle of Man Gambling Supervision Commission | Isle of Man / international operators | Regulates online and land-based gaming; emphasizes transparency and player protection. | Seen as trustworthy and tech-forward, particularly in blockchain-friendly operations. | Early adopter of crypto gambling regulation frameworks and digital verification methods. |
| U.S. State Regulators | U.S. states such as New Jersey, Pennsylvania, Michigan, Nevada | License and audit online casinos and sportsbooks at the state level; enforce fairness and integrity in gaming software. | Highly regulated and state-specific; known for strict compliance and technical certification standards. | Work with independent testing labs (GLI, eCOGRA) to validate RNGs and game math before approval. |
For example, the UKGC has guidelines on their website regarding the rules that gambling operators need to comply with – when it comes to RNGs, it is mentioned that “Random number generation (and game results) must be ‘acceptably random’. Acceptably random here means that it is possible to demonstrate to a high degree of confidence that the output of the random number generators (RNG) is random, through, for example, statistical analysis using generally accepted tests and methods of analysis.”[5] When an operator aims to obtain a license from the UK authorities, this is one of the requirements it needs to fulfill.
Independent Testing Labs
| Testing Agency | Headquarters / Origin | Primary Focus | Scope of Work | Reputation & Notable Details |
| eCOGRA (eCommerce Online Gaming Regulation and Assurance) | London, United Kingdom | RNG testing, payout verification, and responsible gaming audits. | Certifies RNG fairness, RTP accuracy, and operator compliance. Provides the “Safe and Fair” seal recognized by major regulators. | One of the most trusted third-party auditors; it is often required by UKGC[6] and MGA[7] licensees. Publishes transparency reports accessible to the public. |
| iTech Labs | Melbourne, Australia | Statistical analysis and certification of casino software. | Performs RNG, RTP, and game math verification for online casinos, sportsbooks, and lottery systems. | Renowned for mathematical rigor and global reach; accredited by numerous regulatory authorities worldwide. |
| Gaming Laboratories International (GLI) | New Jersey, USA | Comprehensive testing across both land-based and online gambling systems. | Evaluates RNGs, game math, hardware, security systems, and regulatory compliance for casinos and lotteries globally. | One of the largest and oldest testing networks; works with over 480 jurisdictions worldwide. |
| TST (Technical Systems Testing) | Canada (now part of GLI) | RNG verification and software integrity auditing. | Historically provided RNG and game fairness certification before merging with GLI. | Played a major role in early online casino regulation; its standards now form part of GLI’s global framework. |
The certification processes run by testing labs involve running millions of game outcomes through statistical models in order to make sure that the RNG actually produces unbiased, random results. Only after undergoing this type of testing and “passing” can games be offered to players in online platforms.
According to the iTech Labs website, “testing of the Pseudo RNG (Software RNG) is conducted in three stages:
- Examination of Source Code & Compilation
- Identification of RNG algorithm and researching known weaknesses
- Verifying internal state of RNG
- Verifying that the RNG implementation caters for unpredictability and non-repeatability requirements
- Verifying seeding, background cycling and minimal re-seeding
- Verifying the use of the random numbers, including scaling and shuffling
- Compiling the RNG code (after all code issues are resolved)
- Raw numbers generated by the RNG algorithm are subjected to “diehard” tests
- Generating sample scaled output and applying “Chi-square” tests e.g. if the RNG is used to shuffle a deck of cards, then we would apply Chi-square tests to a wide range of shuffled decks”[8]
The Evolution of Rules and Standards
The rules surrounding online casino fairness have grown dramatically over the past 25 years, which is only a natural occurrence considering all of the technological advancements that have happened in the meantime, how much more accessible the internet has become for the entire world and how rapidly and exponentially the industry has developed, plus the ever-inscreasing number of providers that join the market:
1990s – Early 2000s: Patchwork regulations, often depending on offshore jurisdictions like Antigua and Barbuda. Little consistency.
Mid-2000s: Rise of trusted licensing hubs such as Malta and Gibraltar. These jurisdictions are the ones that introduced mandatory RNG testing and ongoing audits.
2010s: Consolidation of global standards, especially in Europe, with cross-jurisdictional recognition of certifications. Responsible gambling measures also became linked to fairness (e.g., transparent RTP disclosures).
2020s and beyond: Continuous compliance testing, AI-driven monitoring and potential for blockchain-based transparency. Regulators now demand ongoing verification, not just one-time certifications.
Challenges and Criticisms
Despite all the advancements and fancy technologies, fairness in online casinos is, of course, not without challenges:
Unlicensed Casinos: Some offshore sites still operate without oversight, offering no real RNG testing.
Fake Certifications: Rogue operators may display fraudulent eCOGRA or iTech logos.
Player Mistrust: Many casual players still suspect games are “rigged”, often due to misunderstanding volatility and probability.
This is not to say that the industry is particularly predisposed to unfair and malicious practices, because it is fair to say that attempts to exploit customers and to make money/profits unethically are part of just about any market, but gambling has an added psychological component to it that may even make some individuals more prone to be deceived. For this reason, experts recommend sticking to licensed casinos that publish RNG audit results and RTP percentages and generally being very attentive to what information online platforms are proud to display or what they seem to avoid mentioning.
The Future of Casino Algorithms
With how rapidly everything is evolving, we can’t even say for certain how the future will look like for online gambling, but one thing we can be sure of is that the next decade could potentially see even greater transparency and fairness:
Blockchain & Provably Fair Gaming: Some platforms now use blockchain-based RNGs – this allows players to verify randomness themselves in real-time.
To dive a little further into this: in provably fair games, players can independently verify that every outcome is genuinely random. Before a round begins, the casino creates a secret number (server seed) and shows a scrambled version of it (hash) to the player. When you play (spin a slot, roll dice or deal cards) the game combines this server seed with your own random input (client seed) to determine the result. Most platforms include a “Verify” button that does all the calculations for you, showing that the outcome matches the original seed. This means you can check that the casino didn’t manipulate the game, all without needing any technical skills.
Example of a provably fair game verification process[9]
AI-Powered Monitoring: Regulators are exploring machine learning tools to detect patterns of manipulation or unfair play.
Global Regulatory Convergence: As online gambling grows, there may be moves toward standardized international fairness rules.
Rounding up
It is safe to say that fairness is the foundation of online gambling – without trust in RNGs, the industry simply couldn’t exist. While spinning reels or rolling dice on a colorful platform with all sorts of cute mascots and flashy banners may seem like child’s play, this is still a place where people gamble real money and can have real losses, so unless there is trust that no one is going to “run off” with your money, you will not be inclined to become a client of these websites.
From the shaky beginnings in the 1990s to today’s sophisticated algorithms and rigorous oversight, online casinos have truly come a long way when it comes to making sure games are truly random and thus fair. Knowing about the existence of the regulators, testing agencies and all the new technologies like blockchain that keep the industry in check, players can feel confident that, at least in licensed casinos, the digital dice are rolling fairly.
The next time you spin the reels or draw a virtual card, there is one thing you need to remember: behind the game there is a very complex system that is essentially designed to protect you; it was built on decades of technological and regulatory evolution that this industry underwent over time.
Sources:
[1] Recommendation for Key Management: Part 1 – General, NIST Special Publication 800-57 Part 1 Revision 5 – Elaine Barker, May 2020
[2] Internet Archive, Cryptologic – 4 July 1996
[3] Behind the Spin: Ensuring Fair Play with RNG Testing and eCOGRA Certification – eCOGRA Learning Zone, 2 August 2024
[4] True Random Number Generators – Mario Stipčević & Çetin Kaya Koç, November 2014
[5] Regulatory returns guidance – UK Gambling Commission, 4 May 2024
[6] Approved Test Houses – UK Gambling Commission
[7] Malta Recognises eCogra standards and testing – MGA, 13 April 2006
[8] RNG Testing – iTech Labs
[9] BCgame Project – Github.io
