What is RNG (Random Number Generator)?
The software algorithm that generates genuinely random outcomes for every spin, card draw, or dice roll at an online casino. All UKGC-licensed casinos must use independently certified RNGs to ensure games cannot be manipulated.
In Depth: RNG (Random Number Generator)
Online casino RNGs are pseudo-random number generators (PRNGs) — mathematical algorithms that produce sequences indistinguishable from true randomness. They generate thousands of numbers per second even when no game is being played; when you spin, the current number is mapped to a reel outcome.
Key properties of a certified RNG:
- Unpredictability: Outcomes cannot be predicted by players or the casino
- Independence: Each outcome is independent of previous results (no memory)
- Uniform distribution: Each outcome has its stated mathematical probability
Certification: UKGC rules require RNGs to be tested by an approved laboratory (eCOGRA, GLI, BMM Testlabs, etc.) before a game can be deployed.
Common myth: The "gambler's fallacy" — believing a machine is "due" a win after a losing streak. Each spin is independent; past outcomes have no effect on future results.
Related Terms
eCOGRA
An internationally accredited testing laboratory and ADR provider that independently audits online casino games, software, and operations. eCOGRA certification confirms games are fair and RNGs function correctly.
RTP (Return to Player)
The theoretical percentage of all wagered money a game pays back to players over an infinite number of rounds. A slot with 96% RTP returns £96 for every £100 wagered on average. The inverse of the house edge.
House Edge
The mathematical advantage a casino has over players on any given game, expressed as a percentage of each bet. The complement of RTP. A game with 97% RTP has a 3% house edge.