Seed

The seed is the starting value that determines the sequence of numbers produced by a pseudo-random number generator. It is the single entry point of the whole mechanism: it, and it alone, fixes the entire sequence that will follow.

A telling image is to see the seed as the page number from which you would start reading a very large book that is already fully written. The content does not change, but the opening point determines everything you will discover next. Two people opening to the same page will read word for word the same story.

The behavior rests on a strict property: from the same seed, the generator always produces exactly the same sequence of numbers, in the same order. This is called reproducibility. Changing the seed, even by a single unit, on the other hand alters the whole sequence that follows. There is therefore no element of chance in the passage from seed to results: everything in it is determined.

The misconception to correct would be to believe that the seed itself makes the draws unpredictable. It is not the seed that creates uncertainty, but the fact of choosing it in an unpredictable way. If you set a known seed, anyone can replay the sequence identically. To guarantee unpredictability, a variable seed is used instead, for example derived from the current instant, different at each launch.

This dual nature explains its usefulness on the site. A fixed seed serves to reproduce a draw in order to test or verify it; a variable seed serves to make each coin flip, each die, and each prize draw genuinely unpredictable from one time to the next.