How RNG & Fairness Work in Online Casinos: A Comprehensive Guide for 2026

During our time testing UK online casinos, we see comments claiming the games are rigged and that it’s not possible to actually win. Is that true, or is it due to a lack of understanding?

This is why we are looking at how random number generators (RNG) and fairness work in online casinos in this guide. If you want to spin some slots and play a few hands of blackjack at one of our recommended sites, it’s important you know how the games work and what’s going on beneath the surface to determine when you win or not.

RNG and Fairness: Key Components of Casino Games

In brick-and-mortar casinos, randomization is achieved through the luck of the draw in card games and through mechanical components and systems in older slot machines. But these things are not available digitally, so game developers have had to create alternative methods to ensure that spins and card deals are random. This is where Random Number Generators come into play, and their associated fairness.

RNG: Random Number Generator

A Random Number Generator is a type of algorithm created by software that continually spits out random numbers within a defined set of parameters for potential values. It’s a system designed to replicate the randomness of a slot reel or the randomness of a draw or deal from a pack of cards.

There are also PRNGs (Pseudo-Random Number Generators), which are increasingly used in online casino games. These still use mathematical algorithms to generate random numbers, but they also start from an initial value, known as a seed. Seed values allow gamers to check PRNG values and provide the best current level of fairness.

The process for an RNG algorithm for a casino game is as follows:

1. The RNG spits out a random number.
2. This number is assigned to a game element (such as a slot symbol or a specific card).
3. The outcome of the spin or other game action is determined.

Step 2 is a key point to remember. While RNG algorithms randomize in-game results, the numbers the RNG generates are ultimately assigned to game elements by the software developer, allowing them to control the RTP (Return to Player percentage).

Fairness: Giving Transparency for Game Results

Fairness is simply what UK online casinos do to make their games and systems fair. This can be used for RNG systems in the games they host, as well as for other features such as competitions, lotteries, tournaments, and prize draws. We expect casinos to operate fairly and to provide information about their practices to ensure an unbiased gaming experience for their customers.

This can include things such as:

• Publishing RTP information.
• Providing provably fair game data.
• Having fairness policies.
• Publishing full bonus T&Cs.
• Providing customers with the option to file disputes.

Pros and Cons of RNG in Casino Games

In our guide discussing how to verify a casino licence, we highlighted fairness, and RNG is undoubtedly the number one way game developers and casinos achieve it. It offers a transparent system with randomised results that players can check themselves. However, the checking process is difficult, and developers can still assign the random numbers to the game elements as they wish.

Pros & Cons

• It ensures all individual results are random.
• The systems are always improving.
• RNG can’t be faked.
• The game results can be published.

• The developers still assign numbers to outcomes.

How RNG Works for Different Types of Casino Games

We’ve got the basics of RNG and what online casinos and game developers do to keep things fair, but how does this look for different types of games? Below, we take a quick look at RNG in action for genres like video slots, table games, and even live game shows.

Video Slots Like Starburst and Duck Hunters

Video slots usually make up a big portion of a casino’s game library - they have epic graphics, awesome bonus rounds, and cool video-game-style graphics and animations. Some of our favorite slots of all-time include Rich Wilde and the Book of Dead, the Fishin’ Frenzy series, and the hundreds of gorgeous games from Pragmatic Play.

But underneath all the flashy gimmicks, you also have RNG algorithms spitting out random numbers to determine the results of your slot spins. Each time you hit that big old spin button, the RNG system will generate a number that will correlate to a specific symbol within the game’s paytable, and this is how you do or don’t get those massive slot payouts.

Card-Based Table Games Like Blackjack

Card-based table games include blackjack, baccarat, poker, Let It Ride, and Pai Gow, for example. Blackjack is easily our favorite as it boasts a 99+ RTP and fast-paced gameplay where you can actually utilise optimum playing strategies. As we said in our online casinos withdrawal guide, these games are often excluded from promotions or subject to lower-weighted wagering requirements due to their higher RTPs.

Now, these games are based on decks of cards. For instance, blackjack typically uses 6-8 decks of 52 cards. With live card games, there is no RNG or digital system. Instead, the human dealers are using actual decks of cards that have been professionally shuffled — your “randomness” is purely down to the actual draws of the cards.

Alternatively, for single-player card games that use digital decks, RNG systems generate random numbers linked to specific cards, such as the Ace of Spades, within a preset set of decks.

Arcade Games Like Aviator

In recent years, we’ve seen arcade games at UK online casinos explode in popularity, and we’ve had a lot of fun with games like crash, dice, mines, Plinko, and HiLo. All of these games rely heavily on RNG systems for their fairness and game results, and a great example is Aviator from SPRIBE.

In our Crash gambling strategy guide, we spoke about this game. It’s played in rounds, and each round, you have to bail out of the aeroplane before it crashes! If you do this successfully, your payout equals your bet amount multiplied by the multiplier shown on the screen when you crash.

For most crash games, an RNG algorithm determines which multiplier the round will crash on before it even starts, and a similar approach is used for other types of arcade games.

Live Game Shows

After live table and arcade games, live game shows are also seeing a surge in popularity, with Evolution leading the way in game design, studio setups, and unique features. Some examples we love playing include Crazy Time, Ice Fishing, Monopoly Live, and Sweet Bonanza Candyland.

As with live table games, live game shows often do not use RNG systems, especially the “Big Wheel” games. For instance, Crazy Time is a big-wheel game featuring a massive game-show wheel with different prize segments. Each round, the human game show host will spin the wheel, and it will land on a single segment — there’s no mathematical algorithm used here — the wheel is actually being spun, and you can see the fairness of the outcome.

Instead, the game developers simply configure the wheel and its prize segments in a specific way to achieve a desired average RTP across spins. For example, Crazy Time has more prize segments with a 1x or 2x payout multiplier, whereas there’s only one of the special Crazy Time segments and two of the other side-game segments like Pachinko and Coin Flip.

What Can You Do to Ensure the Games You Play are Fair?

With this improved knowledge of how RNG & fairness work in online casinos, you can sign up with our recommended operators with confidence. Also, there are things you can do to safeguard yourself and make sure you always have a fair, enjoyable gaming experience:

1. Always Check the RTP (Return to Player Percentage)

One of the points we mentioned in our wagering requirements guide is the importance of a game's RTP. RTP is the Return To Player percentage. It’s an expected amount you should theoretically get back when playing a game over a prolonged period. We have listed the RTPs of some popular UK casino games below as examples:

In practice, for example, if you played £1,000 on Starburst, you would be expected to get back £961.00, or make a £39.00 loss. This is the theory and a guideline — it’s not guaranteed. You could just as easily get an actual RTP of 110% and walk away with more than £1,000 - this is where RNG comes into play. Regardless, the underlying premise is that playing games with higher RTP is preferable.

2. Check the Developer’s Testing Certifications and Licence

Usually, UK online casinos do not create their own games; instead, they work with third-party developers, including Pragmatic Play, Evolution, NoLimit City, Play’N GO, and Blueprint Gaming. Because of this third-party element, it’s important to have a basic understanding of which producers are reputable and have their games licenced in the UK.

You can research the brands yourself. Game developers should hold a licence from the UK Gambling Commission and have their RNG algorithms tested for fairness by third-party testing labs. The top producers will show their certifications and publish their RNG test results.

3. Only Play at Licenced UK Online Casinos

The ultimate safeguard is to stick to licenced UK online casinos. If a site has a gambling licence, it means it has been audited and follows the licence issuer’s regulations and quality standards. In the UK, casinos must have a licence from the UK Gambling Commission.

You can check the licensing information yourself, as it is typically published in the casino’s footer; there will be a licence number and, hopefully, an external link to the official licence page. For a shortcut, you can also check out the banners we have on this page, as we only work with regulated and licenced UK sites that promote fairness and responsible gambling.

Final Thoughts: RNG and Fairness are Not Myths in UK Online Casinos

So, the next time you see people moaning on Reddit and X about rigged games, just think back to this guide on how RNG & fairness work in online casinos. It’s more likely that these people have simply had a string of bad luck or are trying to make a quick buck with ridiculous game strategies.

Simply put, licenced UK online casinos feature games from reputable developers that use RNG algorithms to determine game outcomes and have their systems independently tested for fairness. And you can see a range of these casinos via the banners we’ve got here - just tap on any of them to get signed up and start enjoying some fair casino games.

RNG and Fairness FAQ