Everything a tournament settles on its own, from the number of rounds to the tiebreaks.
Once it starts, a tournament runs itself: it counts the players present, picks the pairing system, fixes the number of rounds and ranks the field. These are the rules it applies, in the order it applies them.
Source: FIDE C.04.1 and FMJD Annex 3, adapted to online play.
One round-based format only, the Italo-Swiss: whoever opens a tournament does not choose between a round robin and the Swiss system, they choose an entry threshold. Alongside tournaments there is the arena, which is a different thing: see the chapter “The arena”.
At starting time the players who actually signed up are counted. Below the threshold the tournament is a round robin: everybody plays everybody, using the Berger tables. From the threshold up it is a Swiss system: each round pairs you with players on your own score, and you never face the same opponent twice.
The default threshold is 7 and can be set between 7 and 20; a round robin takes at most 19 players.
The reason is simple: when a tournament is created nobody knows how many will show up, and picking the format in advance means picking it blind.
A win is 2 points, a draw 1 point, a loss none. With an odd number of players one of them sits out each round: the bye is worth 2 points, like a win — 4 in a two-leg tournament, where every round is two games — but it does not count as a game won, and it does not enter the tiebreaks.
The number is fixed when the tournament starts, from the players actually present. With the default threshold, by number of players:
A tournament takes at most 200 players, so ten rounds is the longest one can get — eleven with the extra round.
In a round robin the rounds are however many it takes for everyone to meet everyone else. With four players both legs are always played, whatever the organiser chose: every round becomes two games and each player gets six, because with only three games a first-round loss would already decide the tournament.
In a Swiss, doubling the field adds one round: every round halves the number of players who can still finish on a perfect score. It is one round more than a knockout would need, because otherwise two players could end up level at the top without ever having met.
Two switches change the count. «Extra round» adds one to the table when the field can carry it, and it only applies if the start produces a Swiss: in a round robin everybody already meets everybody, and one more round would just be a rematch for all. «Two legs», instead, does not add rounds — it fills them: every pairing is played twice in a row, colours reversed and on the same opening, inside the same round, which therefore lasts twice as long. It works the same way in a round robin and in a Swiss, and points stay per game: a win and a draw make 3, two wins make 4.
Anyone with a registered account can open one: no permission is needed and there is no official organiser. Guests and computers do not enter tournaments, neither to open them nor to play them.
One live competition per person: until the tournament or arena you opened has finished or been cancelled, you cannot open another.
A tournament is scheduled, not started by hand: the start time is set between five minutes and fourteen days ahead. Whoever opens it only organises it: to play they must press «Join» on the tournament page like everybody else, and until they do they do not count towards the field — a minimum of 4 means four people besides them.
Seats run from 4 to 200. The minimum to start is 4, and the organiser can raise it: if at starting time there are fewer players than the minimum, the tournament cancels itself. Until it has started the organiser can cancel it; afterwards not, because those already playing are entitled to finish.
A tournament can be private: you get in only with the password the organiser chose, or with the invitation link.
You can sign up until the first round begins, and until then you can also withdraw — cancelling before the start removes you from the standings at once, because you have not played anything yet. From there the door closes both ways: whoever is in stays in the draw, because withdrawing halfway would leave an opponent without a game every remaining round.
It depends on where you were, and the three cases end in three different ways.
If you are simply offline, the game opens anyway and your clock starts. Arriving three minutes late means playing with three minutes less, not losing the game: only if you never arrive do you lose on time. A game one of the two never sat down to does not move either player's rating.
The same applies if you connect and your connection drops before your first move: your clock decides. After your first move, if you drop, you have 30 seconds to come back, as in any game.
If instead you are already busy in another game — an arena, a challenge, another tournament — the round's game does not open at all and you take a walkover loss, with the 2 points going to your opponent. It is not a punishment: opening a second board for you would make the one you are already playing unreachable.
If both of you are missing, the round closes 0-0 and nobody gets anything. An official draw would reward the absence.
In none of the three cases are you thrown out: the next round pairs you as usual.
One last thing applies to everyone: a tournament has an announced duration, and if games are still running at that time they get ten minutes. After that the tournament closes and the games still open are ruled draws.
It depends on how the tournament was opened, and there are nine ways.
«Free move» is the normal one: you play from the first move, and nothing is imposed.
Then come the draws. Three of them place one, two or three random legal moves, and work on every variant. Another four draw from an official F.I.D. table, and exist only on Italian and English, the two variants that have a federal table: what you choose there is how lopsided the opening that comes out may be — up to 1N/1B, up to 2N/2B, up to 3N/3B, or all 174 of them. In a Swiss the same opening never comes out twice in the same tournament.
And then there is the themed tournament: the organiser picks ONE of the 174 official openings, and everybody plays it, in every round and every game. It is the only case where the opening is known before play starts, and the only one where the «never the same twice» rule does not apply — that would be the exact opposite of what a themed tournament asks for.
With two legs the two games of a round are played on the same opening with colours reversed: that is how a lopsided opening stops favouring anyone.
If the tournament is rated, yes — and not in a separate table: tournament games move the same rating as every other game, the one for the variant and the time control being played. The organiser decides, and by default it is rated.
A rated tournament may have a rating floor, that is a minimum rating to get in, in steps from 1000 up to 2000: it is measured on your rating for that variant and that time control, not on a general one. Casual tournaments have no floor, because the rating does not move and there is nothing to protect. There is no ceiling: nobody is kept out for being too strong.
There is then one thing that can switch the rating off by itself, and that is the opening. The federal rule says a single game is enough as long as the opening goes up to 2N/2B; beyond that one colour's advantage is too large for one game to compensate, and two legs are needed. It works both ways: on a draw what counts is the ceiling of the table being drawn from, on a themed tournament what counts is the strength of the chosen opening, which there is known already. If the combination does not hold, the tournament is created casual instead of being refused — and turning two legs on makes it rated again.
Finally, games one of the two never sat down to are not rated.
It depends on the format.
In the Swiss system, in this order:
1. Buchholz Cut 1: the sum of the final scores of every opponent faced, minus the weakest one. It rewards whoever had the harder path. A bye is not counted, because it is not an opponent.
2. Sonneborn-Berger: the scores of the opponents you beat, plus half the scores of those you drew with. It rewards whoever beat the stronger players.
3. The number of wins.
Buchholz and Sonneborn-Berger are the two figures shown next to the points in the standings, shortened to BH and SB.
In a round robin the tiebreaks are different, because everybody plays everybody and Buchholz would separate nobody: first the number of wins, then the result of the direct encounter among the players on the same score, and finally the starting number in the schedule. A round robin's standings still show SB next to the points as information, but the order is the one just described; BH is not shown there, because when everybody plays everybody it is only the mirror image of the points.
The other competition you can open, and it is not a round-based tournament: it has neither rounds nor a schedule, it has a duration. It opens, it runs from ten minutes to eight hours, and while it is open you are paired again as soon as you finish, without waiting for anyone else to finish theirs. You come and go as you like, even once it has started.
With the same person, though, you wait: five minutes for every game already played together. The first rematch comes after five minutes, the second after ten, the third after fifteen, and there is no cap. It keeps an arena from turning into the same match over and over.
Scoring: a win 2, a draw 1, a loss none, as in a tournament. On top of that there is the streak: from the third consecutive win on, every win is worth 3 instead of 2.
And there is the boost, taken before your own first move: it doubles the points of a win and is paid with the clock — the increment goes entirely, and the base time is halved when it is large enough to carry it. It is a bet, not a gift.
On equal points, whoever won more games comes first.