Do True RNGs Exist, and What Do Slot Machines Actually Use?

Do True RNGs Exist, and What Do Slots Actually Use?

When people talk about slot machines being “random,” they’re usually referring to the algorithms behind them—specifically, RNGs, or Random Number Generators. But do true RNGs actually exist? Technically, yes. A true RNG is a hardware-based system that generates randomness from unpredictable physical phenomena—like radioactive decay or atmospheric noise. These are sometimes used in high-security systems or scientific research, but they're rarely, if ever, used in commercial slot machines.

Instead, virtually all slots—both online and land-based—use pseudo-random number generators (PRNGs). These are software algorithms that generate number sequences which only appear random. The reality is, PRNGs are deterministic: if you knew the exact starting conditions (called the "seed") and the algorithm used, you could, in theory, predict the outcomes. But in practice, this is virtually impossible. Modern PRNGs are extremely sophisticated, often drawing from a mix of obscure system variables—things like mouse movement timing, processor load, or memory usage—to constantly update the seed and ensure that outcomes are unpredictable.

As a result, even though slots don’t use true RNGs, their cryptographically secure PRNGs are functionally just as random from a human perspective. They're unpredictable, unriggable, and carefully regulated. This makes them more than sufficient for gambling applications—where the goal is to produce results that feel random, can’t be anticipated, and pass strict testing for fairness. As one slot programmer, u/Trickishwheat8, explains in a Reddit AMA: