Games and product

RNG: how a game picks the outcome of a round

RNG (Random Number Generator) is the algorithm that picks the outcome of every round in slots and digital table games. Each result is random and independent of previous ones, while RTP is set by the game maths, not by the RNG itself.

Yevhen SychovOctober 2026

How it works

At the moment of the bet, the game takes a random number from the RNG and maps it to an outcome using its own table: symbols on the reels, a card, a number on the roulette wheel. It is usually a software algorithm, and the next result cannot be predicted from past ones.

Outcome chance = share of RNG values assigned to that outcomeFor example, an outcome is assigned 1 value out of 10,000: its chance is 0.01% on every spin, even if it hit a minute ago or has not hit for a month.

The game and the RNG usually run on the server of the game provider, not on the operator's platform. In live casino, a real wheel or real cards produce the outcome, but in some game shows the multipliers are also picked by an RNG.

RNG and RTP

The RNG only picks the outcome. Which outcomes exist, how often they hit and how much they pay is set by the game maths, which determines RTP and volatility. The same RNG can sit in games with 92% and 97% RTP.

The operator can choose an RTP version if the provider releases several, but it applies to all players of the brand or market. In a certified game, the outcome cannot be tuned to a specific player or their history: the operator has no access to the RNG.

Who tests it

The RNG and the game maths are tested by an accredited lab: randomness tests, a check against the declared RTP over millions of rounds and a check that results do not depend on past ones. The licence sets exactly what is required. In many markets each game and each RTP version needs a certificate, and in some the RNG test is repeated regularly.

Keep the certificates for your markets at hand: you need them for regulator audits and for answering players in disputes.

Common mistakes

  • Saying a slot is due to pay. A losing streak does not raise the chance of a win. Name game collections by fact: popular, new, biggest wins this week. Copy claiming that a game is paying more often right now misleads players.
  • No ready answer to rigging complaints. Support needs the game certificate, the active RTP version and the player's round history from the provider.
  • Blaming the RNG for a drop in hold. On low turnover, hold jumps around because of volatility. Check the RTP version and big wins first, then contact the provider.
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