Random number generator

How it works

Each number comes from crypto.getRandomValues, the browser's cryptographic random generator, not from a predictable formula. For ranges that fit in 32 bits the tool uses exact rejection sampling: the 32-bit space is divided into whole blocks of the range size and any draw that lands in the leftover tail is discarded and redrawn, so every value in the range is exactly as likely as every other. Wider ranges combine two 32-bit draws into a 53-bit value and scale it into the range. Draws are independent: seeing a number several times does not make it less likely next time, and the tool does not promise to avoid repeats.

Worked example

With the range 1 to 6 each draw lands on any given number with probability 1/6, which is about 16.7%. Two draws make 6 × 6 = 36 equally likely pairs, so two sixes in a row has probability 1/36, about 2.8%. Set the minimum to 0 and the maximum to 99 for two-digit numbers: every pair in that range is equally likely, so 42 coming up twice in a row is exactly as likely as any other pair.

Questions and answers