Swiss system chess pairing by the FIDE Dutch rules

How Swiss pairings work

A Swiss tournament has a fixed number of rounds and nobody is knocked out. Before round 1 the players are ranked, by rating and then by name. After every round they are sorted into score groups: everyone on 2 points, everyone on 1½, and so on.

1. Each score group is split in two by rank, and the upper half plays the lower half: in a group of eight, the first meets the fifth, the second the sixth.
2. Two players who have already met are never paired again, and the colours have to work out (see below). When that is impossible, the pairing changes as little as it can.
3. A player who cannot be paired in their own group floats to the next group down, and meets someone with a slightly lower score.

The player with the most points wins. Equal scores are separated by tie-breaks such as Buchholz (the sum of the opponents’ scores) and Sonneborn-Berger.

Colours in a Swiss

Each player alternates White and Black as far as the pairing allows. Two rules are absolute: no player gets the same colour three times in a row, and nobody’s Whites and Blacks differ by more than two. Only the top scorers of the last round may be exempted. The colour of player 1 in round 1 is drawn by lot, and the others follow from it.

Byes: odd numbers and absences

• Pairing-allocated bye. With an odd number of players one player sits the round out. The FIDE rules give the bye to a player in the lowest score group who has not had a bye or a win by forfeit before. On ChessLivo it is worth 1 point.
• Requested byes. A player who asks to miss a round gets a half-point or a zero-point bye, as your tournament rules allow, and is left out of that round’s pairing.

How ChessLivo pairs a Swiss round

• The FIDE Dutch system. Every round is paired by the rules of FIDE Handbook C.04.3, so a correct program gives the same pairing from the same results; the public tournament page says which system paired it.
• Checked before you publish. ChessLivo checks the round again against the FIDE rules (no rematch, the colour limits, the bye, nobody left out) and shows the organizers any warning. Players see a round only once you publish it.
• Your call. Pair a round again, or edit it by hand. A change that breaks a rule asks you to confirm it, and the round is marked as edited by an organizer.
• One round at a time. The next round is paired once the previous one is published and every result is in.
• Late entries and withdrawals. A player can join between rounds: the rounds they missed count as absences, or as half-point byes where you allow them, and everyone is renumbered. A withdrawn player is no longer paired; their results stand.
• Tie-breaks. By default Buchholz cut 1, Buchholz, Sonneborn-Berger, direct encounter and the number of wins (FIDE C.07); choose your own order.

Step by step, with every button: the Swiss tournament guide.