Random tournament bracket generator

Paste the entrants and the first round is drawn at random. If the number is not a power of two, byes are added so the bracket fits — eleven entrants become sixteen slots, so five people go through without playing.

Single elimination needs a power-of-two field, so any other number means byes. The number of byes is the next power of two minus your entrants: eleven needs sixteen slots and therefore five byes. Rounds are log2 of the padded field — sixteen slots is four rounds. In a seeded competition, byes go to the strongest entrants by design; here the draw is entirely random, which is what you want for a social tournament and not what you want for a ranked one.