Slot Machine Testing: Fairness in Slot Machines

Slot machine testing ensures fairness in the casino games people play. Whether they walk into a land-based casino or play online slots, players must have assurance that their game is fair. Casino operators must know that their slots are legal, while licensing agencies must know the same.

Our guide to slot machine testing explains the full process of slot certification. The article below describes the testing process. It gives details on the licensing agencies and third-party testing labs in the industry. We also provide real-world examples of regulators and designers alike testing slot machines for fairness and safety.




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Key Takeaways:

  • Slot machine testing assures players, casino operators, and regulators that land-based slot machines are fair and secure.
  • Fairness in slot machines means people can bet on games with a sense that electronic gaming machines (EGMs) offer a fair chance at success.
  • Slot machine certification is a multi-step process that includes testing and audits by government regulators and third-party testing firms.

Testing Process:

The testing process for slot machines comes in several stages. Slot manufacturers have their labs to test their latest slot machines. Gambling regulators also test slot machines before certifying them. To ensure the games’ safety and fairness, slot providers, casino operators, and regulators bring in third-party testing firms.

These groups act as consultants and specialists, so they are often the final step before certification. If players want to know the steps regulators take, here are the various tests that slot machines must pass before certification.

How are slot machines tested by regulators?

Slot machines undergo thorough testing by slot designers, government regulators, and third-party firms. Online slots are tested in the same way that land-based slot machines are. Online slot casino designers must consider factors that brick-and-mortar slot developers never consider. Here are what auditors for online casino gambling regulators must consider.

  • Compatibility Testing: The gambling platform operates with other systems. That includes online and mobile devices, web browsers, and operating systems. They test for compatibility with Mac and Windows, Android and iOS systems.
  • Functional Testing: The testers look at the specifications and see if the real-world details match the specs. They’ll test the game configuration setup, gameplay, audio, animations, game kays, and other functionalities in the game.
  • Localization Testing: The game systems must be tested for local peculiarities. Testers must account for languages and other local aspects of the game. Linguistic studies are important, but so are local tax policies and cultural impacts. Gambling laws and government rules must be considered.
  • Penetration Testing: This is security testing, to see if the platform’s whole system, hardware, software, and network are secure. The product must match a regulatory agency’s security specifications. The protocols for deposit and withdrawal encryption are tested. Age verification and geo-location must meet local standards.

The Slot Machine Design and Testing Process

To show where testing and certification fits into the process, let’s take a look at the full slot machine game development process.

  1. Brainstorm Slot Machine Ideas: Come up with the game’s theme and what features it will have. Get an idea for the RTP and the jackpot size.
  2. Conduct Market Research: Once you have an idea, test the concept with market research. Have games with similar themes succeeded or not?
  3. Outlining Requirements: Determine what’s required to handle the technical, mathematical, and artistic requirements for development.
  4. Initial Sketches, Wireframes, and Mockups: Have the development team create conceptual art, mathematical models, and software needed to run the game.
  5. Create a Prototype: Based on the mockups, design a prototype machine. This is used for testing, while making presentations to executives. Once this is greenlighted, develop truly begins.
  6. Design the Slot Game: Once feedback happens on the prototype, the designers start production on the slot game itself. Templates are made for mass production of the slot machine.
  7. Quality Assurance and Testing: Once completed, the slot manufacturer’s lab tests the game for quality assurance. This includes the random number generator, artwork, animation, and sounds.
  8. Testing and Certification: After the game passes the manufacturer’s tests, it is tested again by regulators. Another round of testing assures public safety, fairness, and adherence to regulations.
  9. Launch and Marketing: Now that regulators approve the game, the manufacturer can launch and market the game. The slot machine might appear at the Global Gaming Expo (GGE) in Las Vegas or the ICE Totally Gaming convention.
  10. Licensed to Operators: If it’s a land-based casino, the manufacturer sells the slot machine to the operator. If it’s an online casino, the developer licenses the gaming software to the site.
  11. Updates for the Slot: For safety and improvement, electronic slots undergo periodic updates.

Certification Bodies

Two main types of certification bodies exist — government and commercial groups. Land-based gambling operators receive certification from state and national authorities. Online gambling sites receive certification from national and tribal agencies. Meanwhile, commercial third-party testers offer certification and consult with regulators in either niche.

First, we’ll start with a list of the influential gaming authorities around the globe. Second, we’ll list key organizations that test slot machine manufacturers, brick-and-mortar casinos, and slot site operators. Most such companies have contracts with governmental regulators for auditing and consulting purposes.

What are the regulatory agencies that extend certification to slot manufacturers?

Below are a few of the leading gaming regulators around the globe.

  • UK Gaming Commission: The leading gaming regulator in the world. The UKGC oversees many of the most famous slot developers in the world.
  • Nevada Gaming Commission: The Nevada Gaming Commission and Nevada Gaming Control Board audit casino management and the slot machines in Nevada casinos for fairness and safety. Many international regulators follow the lead of Nevada officials when it comes to laws, policies, and enforcement.
  • Division of Gaming Enforcement: The New Jersey DGE has regulated slot machines in Atlantic City for over 45 years. Like the Nevada officials, the Division of Gaming Enforcement influences around the globe.
  • US State Gaming Commissions: Like Nevada and New Jersey, many US states have their gambling regulators. Examples include the Pennsylvania Gaming Control Board, the Michigan Gaming Commission, the Colorado Division of Gaming, and the Massachusetts Gaming Commission.

What are the organizations that certify slot machines?

Those are some of the leading land-based slot machine certification agencies. Here is a list agencies that certify online slot developers and casino sites.

  • Gibraltar Regulatory Authority: One of the most-used gaming certification agencies in the world. The split between the UK and the European Union after Brexit makes life more complicated for the GRA.
  • Isle of Man Gambling Supervision Commission: The Isle of Man is a British crown dependency and a tiny island roughly equidistant between Northern England, Scotland, Wales, and Ireland. It licenses
  • Malta Gaming Authority: Malta is a part of the European Union, but it is steeped in British Common Law due to its two centuries under British rule. For that reason, it’s a popular choice for European gaming operators.
  • Antigua and Barbuda Directorate of Offshore Gaming: The Caribbean nation of Antigua and Barbuda was one of the first online gaming licensing agencies, starting back in 1994. Antigua and United States have battled in international court over offshore gaming licenses. In its cases before the WTO, Antigua has won.
  • Curacao eGaming: One of the most common licensing agencies for offshore operators who accept US players. Curacao is a Caribbean nation that was once part of the Netherlands Antilles, and is thus steeped in Dutch law.
  • Organization for Economic Cooperation & Development (OECD): The Costa Rican government’s department that oversees online gambling licenses. Like other agencies, it tests the fairness of online slot games.
  • Junta de Control de Juegos (JCJ): The main gaming regulator in Panama. Operators must meet requirements for financial stability, transparency, protection of players’ interests, and secure gaming technology.

Are other groups involved in the slot machine certification process?

Many companies and watchdog groups test slot machines for fairness. Most auditors are companies like BMM Testlabs, iTech Labs, GLI, Technical Systems Testing, and TriSigma. Others are watchdog groups like eCOGRA. Many consult with government regulators, such as SIQ, QUINEL, iTechLabs, and TST.

European Testing Labs

  • BMM Testlabs: Has over 40 years of experience in private independent game testing. BMM Testlabs has 15 offices on six different continents. It works for manufacturers, operators, and regulators alike. It provides testing, regulatory consulting, and field services for famous gaming authorities worldwide.
  • iTechLabs: An accredited laboratory for online gambling certification and quality assurance testing. iTechLabs has a combined 100 years of experience and testing and certification. Its compliance testing includes casino and multiplayer games, platform audits, RNG testing, and RTP/RNG output audits. With locations in Australia, Asia, and Europe, iTech Labs has been in operation since 2004.
  • TriSigma BV: TriSigma BV provides compliance, test services, and type approval for gaming industry firms and authorities alike. It has testing facilities in the Netherlands and Spain, and provides a full range of services: certification, testing, inspection, auditing, training, forensics, and regulatory services. It handles RNGs, casino management systems, linked jackpot systems, information security systems, and player monitoring.
  • SIQ: SIQ offers testing and certification of products, management system assessment, IT assessments, calibration and inspection, explosion protection, and training services.
  • QUINEL: Quinel is an international testing lab based out of Malta, the United Kingdom, and Italy. It handles online gambling and land-based testing while addressing information security, PCI DSS assessments, and certifications. Quinel works with 21 jurisdictions worldwide, ranging from the United Kingdom, Ontario, the Baltic States, and Spain to the Philippines and Argentina.

Australian Testing Labs

  • Gaming Laboratories International (GLI): Tests all manners of electronic gaming equipment. Its staff includes hardware and software engineers, mathematicians, system engineers, compliance engineers, and qualify insurance specialists. Has offices in Spain, Italy, Austria, Canada, South America, Puerto Rico, Asia, and Melbourne. Been in operation since 2000. Its tagline is “Where the Game Begins.”
  • Technical Systems Testing (TST): TST is a third-party auditor for gaming operators, software supplies, manufacturers, and regulators. Handles evaluations for hardware, software, RNGs, field data analysis, communications, game mathematics, central monitoring systems, and server-based gaming systems. Has office locations in London, Vancouver, the Netherlands, Italy, Manila, and Macau. In operation since 1993 and has been a subsidiary of GLI since 2010.

Online Casino Industry Watchdog Groups

  • eCOGRA: UK-based integrity assurance group that’s help with compliance issues since 2003. eCOGRA is an industry watchdog group that audits gaming operators and publishes results every month. It works with world-famous groups like SportRadar, Thunderkick, Betway, 888 Holdigns, Habenero, 32Red, Bet365, Danske Spill, and Microgaming for the sake of player protections.

Real-World Examples of Testing and Certification

The certification process varies somewhat from one laboratory to the next, but they follow similar practices worldwide. Here are cases of testing and certification for real-world slots.

Testing Brick-and-Mortar Slot Machines

Let’s look at real-world examples of slot testing. Imagine a slot machine designed for a London casino. Regulators from the UK Gaming Commission would test that slot machine’s RNGs in several ways. First, they would take a look at the algorithm used in the machine. They could test it mathematically by looking at the probability of each separate potential result.

Second, they could test how the RNG’s results would work in practice. With powerful computers, actuaries could run the RNG through a billion simulated spins. While a hundred or a thousand or ten thousand spins might produce wildly different numbers, the results of a billion spins are likely to match the probable results. If something is way off, then the auditors would see it in these simulations.

For land-based slot machines, regulators might even test a slot in a real-world setting. That’s usually what a slot manufacturer does, as they have their testing labs on the site of their manufacturing plants. Testing labs for land-based slot machines use certain tests that online slots don’t require. They test the slot cabinet’s mechanical parts to see if they work. That includes the game screen, the seating, lighting and soundboards, and the controls.

Certification of Online Slots

Online slot games work similarly to brick-and-mortar slots, as both use an RNG to create truly random results based on a complicated algorithm. The mechanical parts on a land-based slot don’t exist (and therefore aren’t tested) for online slots. That means the testing of the RNG, algorithm, and corresponding variance is most important.

Therefore, the certification process involves regulators and third-party auditors testing the RNG and algorithm. Compatibility with mobile devices and desktop computers must be tested, but most of it involves the math of the game.

How do slot machines’ random number generators work?

Game designers use special computer chips for random number generators, which create truly random result. To do so, the slot designer creates an algorithm with every possible reel combination. The probability of each possible reel combination is added to the algorithm, so jackpot combinations are much less likely to happen than less complicated patterns.

Readers might be wondering what an algorithm is. Before continuing, we’ll address that question.

What is an algorithm?

The Oxford Dictionary defines an algorithm as a “process or set of rules to be followed in calculations and other problem-solving operations, especially by a computer.” Examples include driving directions, a recipe for baking a quiche, or instructions on finding a library book, these directions are an algorithm.

The testing team takes a look at the algorithm to see whether the payout is the exact amount specified. If a slot machine has a 96% payout percentage, then the auditors test the RNG to see if the payout tables yield the probability of 96% payouts. To do that, they must plug all the functional specifications into the algorithm. Once this happens, each result produced is truly random.

Slot machine RNGs produce thousands of random results per second. When a player hits “Spin,” the game systems use the most recent result for the outcome of the spin. Then the computer graphics simulate the appropriate reel combination as a visual aid to the player. The reels don’t reel spin as they did with mechanical slots. It’s the RNG that produced the result.

How are slot machines tested for fairness?

Testing labs study the return-to-player (RTP) or expected payback by studying the algorithm in depth. Once the auditors pull apart every bit of the equation and test every single calculation, they can know the accurate expected return. When they test the RNG, they see whether it produces true random numbers.


The slot machine industry is based on trust, so players should look at a slot’s certification. If players don’t trust that casino operators host safe, secure, and fair games, they won’t play. If the casino can’t assure players their slots are fair, then they won’t buy or license slot games from providers. Regulators won’t extend licenses, so the whole industry is based on testing and certification.

If you have questions about the slot machine testing, refer back to this page. The various organizations involved in certifying slot machines don’t change often, so read our guide to slot testing for a quick reminder of the players.

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