📖Guides to Randomness and Fair Draws

Every tool on this site takes a second to use and about four seconds to distrust. Somebody in the room always asks whether the wheel is really random, whether the coin favours heads, or why the person running the draw was allowed to press the button twice. These five guides answer that category of question properly, with the arithmetic shown.

How to make a custom spinner wheel is the practical one: entries in a text box, weighting by duplicate lines, sharing a whole wheel in a single link, and putting one on your own page. Is a coin flip really 50/50 takes the physical coin apart — Diaconis, Holmes and Montgomery predicted a same-side bias of about 51%, and in 2023 a team led by Bartoš tested it across 350,757 recorded flips and found 50.8%. Fair ways to pick a giveaway winner is about the process rather than the generator, because nearly every dispute over an online draw is about the entry list, not the number.

How random is random is the technical core: what separates a pseudo-random generator from a cryptographically secure one, why Math.random is the wrong tool for a draw, and how a naive % 6 on a random byte quietly favours the low faces. Secret Santa rules that actually work covers the arrangements that prevent a gift exchange going wrong, including why a random pairing avoids self-matches only about 36.8% of the time.

Nothing here is padded with the same paragraph rewritten five ways. If you only want the result rather than the reasoning, start with the wheel spinner and come back afterwards — the methodology page is the short version of all of it.