RNG (Random Number Generator)
The software (or hardware) that decides the unpredictable outcome of a digital gambling game — which cards, reel stops, or numbers come up — so every result is down to pure chance.
Definition
In iGaming, a Random Number Generator (RNG) is the algorithm or physical device that produces the outcomes of digital games where no live equipment is used — slot reel positions, card and dice values, roulette numbers. Most online games rely on a pseudo-random number generator (PRNG): a deterministic algorithm seeded from an entropy source that generates long, statistically uniform sequences which pass standard randomness tests, while a hardware or "true" RNG (TRNG) draws directly from physical noise and is often used to seed the PRNG. Crucially, the RNG only decides which outcome occurs, with each result independent of the last and (for a given draw) equally likely; the game's payout structure — the paytable — is what sets the RTP and house edge, not any bias in the RNG itself. Before a game goes live, its RNG is typically tested and certified by an independent laboratory against the standards of the relevant licensing jurisdiction.
Worked example
Consider European roulette with a single-zero wheel of 37 pockets (0–36). The RNG selects one number, and because its output is uniform, each pocket is equally likely — a probability of 1/37 ≈ 2.70% per number, independent of every previous spin. A winning straight-up bet on one number pays 35 to 1, even though the mathematically fair payout for a 1-in-37 chance would be 36 to 1. That one-unit gap — not any rigging of the RNG — is where the house edge comes from: the expected value of a $1 straight-up bet is (1/37 × +$35) + (36/37 × −$1) = −$0.027, i.e. a house edge of 2.70% and an RTP of 97.30% (2.70% + 97.30% = 100%). The RNG is perfectly fair; the edge lives entirely in the paytable.
Why it matters
RNG is the foundation of fairness and integrity in online gambling: it is the reason each spin or hand is independent, why no machine or game is ever "due" to pay (the gambler's fallacy), and why regulators require independent testing before a game may be offered. For a player, understanding it clarifies that outcomes cannot be predicted or influenced by tracking past results, and that betting systems do not change the underlying odds — an important guardrail for informed, responsible play. For an industry professional, the RNG sits at the centre of game certification, licensing conditions, and the player-trust obligations that let an operator hold a licence at all.
Related
Note: Stable definition of the concept. The named certification bodies (e.g. GLI, eCOGRA, iTech Labs, BMM Testlabs), the exact randomness standards, and re-testing requirements vary by jurisdiction and licence, so treat those as illustrative rather than universal. The roulette figures assume a single-zero European wheel (37 pockets, 2.70% house edge); double-zero American roulette has 38 pockets and a 5.26% house edge. Note also that live-dealer games use physical equipment, not an RNG, for their primary outcome.