An often overlooked major feature on Challonge.com is the Swiss tournament format. While running a Swiss tournament on paper is a nightmare, we've taken the pain out of it to bring its many advantages over traditional brackets to light.
Swiss tournaments give equal play time to participants, pair players with others of similar skill level, and determine a winner in far fewer rounds than you'd anticipate. They're essentially smarter, abbreviated round robins.
First RoundTop seeds are paired against bottom seeds. Random seeding should be used if no ranks exist. For 8 players, the pairs would be 1v5, 2v6, 3v7, and 4v8.
PointsMatch wins are awarded 1 point, ties 1/2 a point, and byes 1 point (or as configured). For multi-set/game matches, you may opt to award points for set/game wins as well - this gives match losers a chance at partial credit.
Additional RoundsAfter each round, players are grouped by score. The top and bottom half of each group is then paired (same method as the first round), but steps are taken to ensure there are no rematches. Players float up or down between groups if necessary. When there's an odd number of players, a bye is awarded to the lowest ranked player who has not yet received one.
The minimum number of rounds to determine a winner is equal to the binary logarithm of the number of players rounded up (3 rounds for 8 players, 4 for 16, 5 for 32, and so on). On Challonge, you can opt to play more rounds than the minimum for more definitive results.