Swiss rules

1. Everyone plays every round. Each round you meet someone on the same points as you — or as close as possible.
2. You never meet the same player twice unless it's impossible to avoid.
3. Within the same points, the pairing is a random draw — not the standings, the table numbers or the order of registration.
4. A win gives 3 points, a draw 1. On equal points, OMW%, GW% and OGW% decide, in that order.
5. If there are playoffs, they are seeded from the standings: no. 1 meets the lowest seed, and no. 1 and 2 can only meet in the final.

Draw or flip. The organizer chooses when creating the tournament. With Chaos Orb flip — the default — a drawn game score is settled with a flip, so the match gets a winner with 3 points. The games still count as played: 1–1 is 1–1 in GW%. With Draws allowed both get 1 point.

Bye. With an odd number of players, one sits out and gets 3 points, recorded as 2–0. The bye is kept entirely out of the percentages — both yours and your opponents' — so it neither helps nor hurts your tiebreakers.

The app recommends a number of rounds based on the field, so that after the last round there is usually only one player without a loss. The organizer can choose a different number. Swiss requires at least 4 players.

Each round is paired from the points everyone has after the previous rounds. Players with the same points form a score group, and you are preferably paired within your own. If a score group doesn't add up, one player floats down and meets someone from the group below.

What weighs the most

The pairing is calculated for the whole field at once — not table by table from the top — so a choice in one place never forces a bad pairing somewhere else. The rules have a fixed order, and a rule further down is broken rather than one further up:

1. Nobody gets a second bye until everyone else has had one.
2. Nobody meets the same player twice. If it can't be avoided, there are as few rematches as possible.
3. The bye goes to the lowest points group — as close to the bottom as possible.
4. As few and as short pair-downs as possible. A pair-down across several points groups weighs more than two short ones: 6 vs 3 and 3 vs 0 is better than 6 vs 0.
5. Within all of this, the draw decides — including who in the bottom group sits out.

This means, for example, that the bye can move up a points group if that's the only way to avoid two players meeting again. Every time a rule is bent — a pair-down, a rematch, a bye outside the bottom — it's noted on the round, so the tournament administrator can see why.

The random draw

The order within a score group is a random draw that is reshuffled every round. It is calculated from the tournament, the round and the player, so it differs from night to night and from round to round — but stays the same if a round is cancelled and re-paired. So it isn't the standings that decide whom you meet within your points: the leader doesn't necessarily meet no. 2.

The standings are sorted by points. If players are tied, the tiebreakers decide in this order:

1. OMW% — your opponents' average match-win percentage. How strong were the players you met?
2. GW% — your own share of the games: games won give 3, drawn games 1, divided by 3 × games played.
3. OGW% — your opponents' average GW%.

Match-win percentage is a player's points divided by 3 × number of matches. Byes and awarded losses don't count, and an intentional draw counts as a match worth 1 point.

The 33% floor. In OMW% and OGW%, each opponent counts as at least 33% — so you aren't punished hard for having met someone who lost everything. Your own GW% has no floor.

Dead even. If two are level on points and all three tiebreakers, they share the placing in the standings. If a cut to the playoffs has to separate them, the one who registered first goes ahead.

Late arrivals can only join while round 1 is in progress. The tournament administrator chooses: either the late arrival plays the player who had the bye — and the bye's 3 points disappear — or the late arrival starts with a round 1 loss worth 0 points, outside all percentages. From round 2 the field is closed.

If you drop, you're not paired any more. Your played matches still count — both for you and in your opponents' OMW% — and you keep your place in the standings, but you can't advance to the playoffs.

If the tournament has playoffs (Top 2, 4, 8 or 16), the best active players in the Swiss standings advance and are seeded by their placing. No. 1 meets the lowest seed, and the bracket is laid out so the top two can only meet in the final:

The winner advances, and the winner of the first match meets the winner of the second. Playoff matches don't count in the Swiss standings. Players knocked out in the same round are ranked by their Swiss placing: if two lose in the semifinals, the one placed higher after the Swiss rounds gets 3rd place.

Only public Swiss events count towards the rating. Everyone starts at 1500, and every decided match against an opponent moves the rating — most for a win over a stronger player. Byes, no-shows and awarded results don't count, and under ten matches the rating is provisional. The rating is calculated when the tournament is finished. See the rating list.

Each format has its own rating: Old School, X-Point and Premodern don't share a pool, and an event counts in the format it was created in. Two-Headed Giant has no rating yet.