An online casino RNG supplies unpredictable values that game software maps to outcomes. For games offered under a Great Britain remote licence, the Gambling Commission requires applicable random results to be “acceptably random”, and specified fairness elements must be independently tested before release. That supports confidence in the tested system; it does not predict or guarantee your next result.
How an RNG becomes a game result
The Gambling Commission’s testing requirements treat the RNG, the conversion of its output and the game rules as connected parts of one result chain:
- The RNG produces raw output. Its algorithm, implementation and any seeding or reseeding must not introduce predictable results.
- Scaling or mapping converts that raw output into the range the game needs, such as a reel position, card selection or numbered outcome. The conversion must preserve the required randomness and expected probabilities.
- The game logic applies the published rules, paytable and features to that mapped outcome. Testing therefore has to check more than the raw number generator.
Why a streak does not reveal the next result
What independent testing checks
- RNG documentation, the algorithm or hardware, and any publicly known weaknesses.
- Source code, to check that the implementation matches the documented design.
- Statistical behaviour of raw output and any scaled output or shuffled-deck data.
- Game mathematics, displayed rules, artwork, paytable and theoretical return to player.
- The implemented game in an environment reflecting intended live use, including simulated, emulated and manual testing where appropriate.
- The mapping that turns RNG output into actual game outcomes.
For the products covered by the testing strategy, satisfactory testing is required before release and the report must be supplied to the Gambling Commission. Changes capable of affecting fairness can require further testing. Applicable annual audits also sample software updates, review change controls and confirm that live return-to-player monitoring processes exist.
What testing can and cannot prove
- It can provide evidence that the tested RNG output, mapping and game implementation meet the applicable standards.
- It can compare simulated or observed game performance with the game’s expected mathematics.
- It cannot tell you which result will occur next.
- It cannot make every short run resemble the long-run probability or theoretical RTP.
- It cannot guarantee that you will win or recover money. A fairly implemented game can still have a house edge and produce losses.
- It is not a substitute for checking that the website you are using belongs to a licensed business.
A practical fairness-check checklist
- Match the business, trading name and website domain against the Gambling Commission business register.
- Open the game rules and information before play. Check that the payouts, features and theoretical RTP are stated clearly.
- Treat a testing logo or certificate reference as a lead, not final proof. Confirm that the testing organisation appears on the Commission’s current approved list.
- Check whether the product is RNG-driven or live-dealer. Live-dealer games use separate controls for equipment, dealing, supervision, surveillance and auditability.
- Use a simple decision rule: if you cannot match the domain to the licensed business, cannot find the rules and RTP, or see information that conflicts, do not use the game until the discrepancy is resolved.
RNG games and live-dealer games are not the same
A streamed live-dealer game may use physical equipment and dealing procedures rather than software alone to determine the result. The Gambling Commission requires live-dealer operations to be fair and independently auditable, with controls covering equipment, trained staff, supervision, video surveillance, restricted access and game logs. Check the type of product before deciding which fairness signals matter.
Official sources
- [Gambling Commission: RTS 7 — generation of random outcomes](https://www.gamblingcommission.gov.uk/standards/remote-gambling-and-software-technical-standards/rts-7-generation-of-random-outcomes)
- [Gambling Commission: procedure for RNG and game testing](https://www.gamblingcommission.gov.uk/strategy/testing-strategy-for-compliance-with-remote-gambling-and-software-technical/3-procedure-for-testing)
- [Gambling Commission: approved test houses](https://www.gamblingcommission.gov.uk/licensees-and-businesses/guide/page/approved-test-houses)
- [Gambling Commission: register of gambling businesses](https://www.gamblingcommission.gov.uk/public-register/businesses)
- [Gambling Commission: RTS 17 — live-dealer studios](https://www.gamblingcommission.gov.uk/manual/remote-gambling-and-software-technical-standards/rts-17-live-dealer-studios)