RNG stands for random number generator, the software that decides the result of every digital slot spin, virtual roulette spin and RNG card hand in a casino app. It runs on the game provider’s servers, not your phone, and in Great Britain it must be independently tested before a game can be offered.
An RNG picks each result at the moment you play; nothing on your phone influences it.
Every spin or hand is independent, so a game is never ‘due’ to pay.
UK-licensed games are tested by independent test houses before release.
Live dealer games use real cards and wheels instead of an RNG.
Stands for
Random number generator
Used in
Slots, RNG table games, scratchcards, Slingo
Not used in
Live dealer games (physical equipment)
Runs on
The game provider’s servers
Checked by
Independent test houses
What RNG means in a casino app
A random number generator is a piece of software that produces a constant stream of numbers with no predictable pattern. Casino games use those numbers to decide outcomes: which symbols land on a slot’s reels, which pocket a virtual roulette ball falls into, or which card comes next from a digital shoe.
Strictly, most game RNGs are pseudo-random: they use a mathematical formula started from a seed value, but the formula is designed and tested so that its output can’t be predicted or reproduced in practice. For a player the effect is the same as true randomness. Each result is independent of the last one and of the next.
How an RNG turns a tap into a result
When you tap Spin in a slot inside an app, the request goes to the game provider’s server. The RNG draws numbers at that instant and the game maps them to outcomes, for example one number per reel, each pointing to a stop on that reel’s strip. The server records the result and sends it back, and only then does your phone play the animation of reels spinning and stopping.
A simple worked example: a virtual European roulette wheel has 37 pockets, so the RNG must give each pocket an equal 1 in 37 chance, about 2.70%. Over a long test of millions of spins, each number should appear close to 2.70% of the time, and testers check that it does. A slot works the same way at a larger scale, with the reel strips and paytable setting the RTP and house edge.
Because the outcome is fixed before the animation starts, nothing you do during the spin, such as tapping the screen, can change it. That is also why UK rules banned slam-stop: it only ever changed the animation, never the result.
RNG games vs live dealer games on your phone
Casino app lobbies mix both types, often with the same game names, so the labels matter.
RNG game
Live dealer game
How results are made
Software random number generator
Physical cards, wheels or dice
Pace
At least 2.5 seconds per slot spin; 5 seconds per round for other casino games
The UK Gambling Commission’s technical standards require games offered to British players to be fair and tested. In practice that means the game studio sends the game and its RNG to an independent test house, such as GLI, BMM or eCOGRA, which checks that the output is random and that the paytable delivers the published return. Changes to a game after release need retesting.
Casinos usually explain this on a fairness or responsible gaming page, sometimes with a test house logo in the footer. The full process is covered in how casino apps are tested, and the separate question of whether apps can be trusted is answered in are casino apps rigged?. To confirm an operator is licensed at all, use the steps in how to check a casino licence.
RNG myths that don’t hold up
‘The game is due a win.’ Each result is independent, so a long run without a bonus doesn’t make one more likely next spin.
‘Apps pay less than the website.’ The app and website are front ends to the same account and the same server-side games.
‘Wi-Fi or mobile data changes the odds.’ Your connection only carries the result; it doesn’t create it.
‘Clearing the app cache resets my luck.’ Cached files are graphics and sound, with no link to outcomes.
‘A near miss means a win is close.’ A near miss is just one of many random outcomes, and UK rules stop games presenting losses as wins.
Randomness also means losing streaks are normal. Over time the house edge applies, so treat play as paid entertainment and set a budget with the tools described in casino app limits.
Where you see RNG mentioned in an app
Look in three places: the table game category, where titles may be marked RNG or virtual to separate them from live versions; each game’s help or information screen, opened from the ‘i’ or menu icon, which describes the rules and return; and the casino’s terms or fairness page. Related terms: volatility, hit frequency and the wider casino app glossary.
Both apps run RNG slots from well-known studios. Coral gives new players 100 free spins at 10p each when they bet £10 on slots, and PlayOJO gives 80 spins on Big Bass Bonanza after a first deposit of £10 or more, with winnings paid as cash. 18+, terms apply.
Significant terms: 18+. New players only. Offer runs 01/10/2026 to 01/02/2027. Deposit (certain types excluded) and bet £10+ on slot games to get 100 free spins (selected games, £0.10 each, 48 hrs to accept, valid 7 days). No wagering on free spin winnings. Deposits by Neteller, PayPal, Paysafe, Skrill, prepaid cards and certain debit cards do not qualify. Restrictions and T&Cs apply. GamCare.org.uk
Read the Coral reviewLicence: LC International Limited, UKGC account 54743. Offer checked 5 October 2026.
Significant terms: 18+. New UK customers (excluding Northern Ireland). First deposit only. Minimum deposit £10. 80 free spins on Big Bass Bonanza, £0.10 each. No wagering requirements; winnings paid in cash. Cannot be used with any other offer. Only available to players who arrive through the designated offer link. Full T&Cs apply. GamCare.org.uk
Read the PlayOJO reviewLicence: Skill On Net Limited, UKGC account 39326. Offer checked 5 October 2026.
18+. Gambling should be entertainment that costs money, not a way to make it. Set a deposit limit before you play: how to set limits. Free, confidential help: National Gambling Helpline 0808 8020 133.
Frequently asked questions
What does RNG stand for in a casino?
RNG stands for random number generator. It is the software that produces the unpredictable numbers used to decide results in digital casino games, including slots, virtual roulette, RNG blackjack, scratchcards and Slingo. Every spin or hand draws fresh numbers at the moment you play, so results don’t follow patterns or depend on what happened before. Live dealer games are the main exception, because they use real cards and wheels filmed in a studio. See how casino app games work for the bigger picture.
Are RNG games in UK casino apps fair?
Games offered by UK-licensed casinos must meet the Gambling Commission’s technical standards, which require independent testing of the random number generator and the game’s return before release. Fair means random and matching the published rules and RTP; it does not mean you will win. Every game has a house edge, so over time players as a group lose more than they win. Stick to casinos you can find on the Commission’s public register, as explained in how to check a casino licence.
Does the RNG work differently on a phone than on a computer?
No, the RNG runs on the game provider’s server, so the device you use has no influence on it. Your iPhone, Android phone, tablet or laptop sends the request to play and displays the result the server returns. That is why the same slot has the same rules and return whether you open it in an app, on the mobile site or on desktop, provided the casino runs the same RTP version. The app vs mobile site guide explains what does differ, such as login options and notifications.
Can a casino change the RNG to make me lose?
A UK-licensed casino can’t alter a game’s random number generator. Games are built and certified by the studio, tested independently, and changes need retesting. What casinos can sometimes choose is which certified RTP version of a slot to offer, such as a 96% or 94% version, and that figure appears in the game’s help screen. The RNG itself stays random for everyone. If you think something is wrong, complain to the operator and then, if needed, to an ADR service.
Is there a pattern or trick to beat an RNG?
No, a properly tested RNG produces no pattern you can use. Systems based on timing your taps, changing stake after losses or waiting for a game to be due don’t change the odds of any single spin, and staking more to chase losses is a common route to spending more than planned. The house edge applies to every bet. Practical control comes from budgets and limits rather than tricks: see bankroll management on mobile and set a deposit limit before you play.
Do live casino games use an RNG?
Mostly not. Live dealer games such as live blackjack and live roulette use physical cards, wheels and shoes, filmed in a studio and streamed to your phone, so the dealer and equipment determine the result. Some live game shows add RNG elements, for example random multipliers applied before a round, and the game’s help screen explains how they are chosen. If you prefer physical randomness you can see, the live casino apps page explains how mobile live tables work.
Where can I see that a game’s RNG has been tested?
Start with the casino’s footer and its fairness or terms pages, which often name the testing laboratories used or show their logos. Game studios frequently publish certification details for their titles too. Inside an app, the game’s information screen shows the rules and RTP, but rarely the certificate itself. The most important check is that the operator holds a Gambling Commission licence, because testing is a licence requirement. Our guide to how casino apps are tested explains what test houses look at.
Gambling can be addictive. Free, confidential help is available 24 hours a day from the National Gambling Helpline on 0808 8020 133. Get support from GamCare or NHS gambling support, or block yourself from all UK-licensed gambling sites with GAMSTOP.
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