Slack Bracket lets you fill in the parts of your March Madness bracket that you want to fill in, and generates winners for everything else. You can simulate winners for just one matchup, or the entire tournament. Or anything in between.
All data used in the site is provided by FiveThirtyEight. This includes information about each team, including bracket location and a team rating. For every matchup that you don't pick a winner, those team ratings are used to decide which team. This ensures that there is a statistically likely amount of upsets in the tourney (excluding matchup winners manually chosen by the user), and those upsets will follow a statistically optimal distribution.
Mostly because I thought it would be a fun project. Also, I'm sure it makes some kind of statement about the inherent randomness and unpredictability of the tournament or something.
This site has been used to create multiple top-1% brackets in a small sample size, including this one in 2021 that ranked in the top 0.2% on ESPN. Of course, that could be coincidence, but why take that chance?
Awesome! You can help out by raising an issue or submitting a PR.