Random number generator (RNG)
A random number generator (RNG) is the software that produces the unpredictable numbers a casino game turns into spins, cards and dice rolls.
Also called RNG, random number generator, PRNG
Every online slot, digital card game and dice game runs on an RNG. The game asks for a number, then maps it to a result using its rules, such as which symbols land. The mapping sets the odds and the RTP. The RNG only supplies the randomness. Regulators that set technical standards require the output to be unpredictable, and independent test labs check it.
Example. You press spin. The game draws numbers from the RNG at that moment and maps them to reel positions. The animation then shows a result that is already decided. Stopping the reels early, or spinning at a "lucky" time, changes nothing.
What people get wrong. People think an RNG runs hot and cold, or pays less after a big win to balance its books. A properly built RNG has no memory, and each result is independent. Great Britain's technical rules ban games that adapt to earlier results. The belief that a result is due is the gambler's fallacy.
The limit of an ordinary RNG is that you cannot check it yourself. You rely on the game provider, the test lab and the regulator. A provably fair game lets you check that the casino did not change its seed after you bet.
Related terms
- Provably fair
Provably fair is a system that lets you check for yourself that a casino fixed its part of a bet's result before you bet and did not change it afterwards.
- Game provider
A game provider is the studio that designs and runs a casino game, which the casino then offers to players on its own site.
- Return to player (RTP)
RTP (return to player) is the share of all money bet on a game that it is built to pay back to players over a very large number of bets, shown as a percentage.
- Gambler's fallacy
The gambler's fallacy is the mistaken belief that a random result is more or less likely to happen because of what happened in earlier rounds.