A bye is a special privilege given to a team in the initial rounds because of which it gets exempted from playing in the first round and directly enters the second round. In knock-out (single-elimination) tournaments, if the number of participants is not a power of two (e.g. 16 or 32), one of the methods used to make a working bracket are byes which automatically move certain participants into a later round without requiring them to compete in an earlier one. Although it may not be necessary based on the format of the tournament, other types of eliminator tournaments may also include a bye for other reasons, such as to reward the best ranked participant(s).
In round-robin tournaments where there are an odd number of competitors, usually one competitor gets a bye in each round, as it is impossible for all competitors to play in the same round. However, over the whole tournament, each team plays the same number of games as well as sitting out for the same number of rounds during the tournament.
Similar to the round-robin context, in leagues where almost all teams play on the same days in regular-season play, a team that does not play on a given day is said to be on bye. In sports that are played weekly, especially football, a team that does not play at all during a given week is said to be on its "bye week". (This definition is chiefly U.S.)
In a standard single-elimination tournament, each round has half the number of teams as the preceding round. Thus the finals will have two, the semi-finals will have four, the quarter finals will have eight, etc. Thus tournaments with competitors numbering a power of two can have a standard bracket in which all teams are paired up with the loser of each match eliminated and the winner moving on to the next round until only one champion remains.
However, if the number of teams is not a power of two, a simple elimination tournament will eventually produce a round with an odd number of teams (if the number is not odd to start with). For example, a tournament of nine teams could only have four matches in the first round, while a simple tournament of ten teams would produce a second round with five teams, meaning only four matches could occur.
One method of allowing more teams to compete in tournaments is to give one or more teams a bye which allows them to automatically pass to a subsequent round without competing. Most commonly the teams with the highest ranking going into the tournament are given a bye to the second round, as it is generally seen as an advantage to be assured entry into a later round. In the NFL playoffs, for example, the top two division-leaders in each conference are given byes to the second round. The Canadian Football League (CFL) also grants a bye to its two division winners, directly to the division finals as four other teams compete in a semi-final week. In other tournaments where teams are unranked, random draw may be used to determine the byes.
The number of teams offered a bye is generally designed to ensure that the next round consists of a power-of-two number of teams so the tournament can proceed as a simple single-elimination tournament from that round onward. While less common, byes can be offered for multiple rounds (e.g. giving a bye directly into the third round), or starting in a later round (e.g. the top-ranked team in the first round is given a bye straight to the third round). In the English FA Cup, the football clubs in the top two league divisions receive two-round byes and enter in the third round "proper" (of eight); the two next-highest divisions' teams will have entered in the first round. Another example is the UEFA Europa League. The WNBA also grants double byes to the league's top two seeds, while the next two seeds get first-round byes for their playoffs.
If the byes are all single-round byes into the second round of a tournament, the number of byes required is the difference between the number of teams and the next-highest power of two. For example, a 12-team tournament will require four byes (16-12) to ensure that instead of six teams in the second round, eight advance (as the four byes avoid two of the four teams being eliminated).
A bye granted in a later round of the tournament eliminates the need for two byes in the previous round. For example, the same 12-team tournament could grant two byes in the second round instead of four in the first. This would result in six teams in the second round with two advancing automatically to the third. It could also grant a single bye in the third round.
In certain tournaments, the byes are somewhat disguised. Since 2012, the Major League Baseball playoffs has included ten teams consisting of six division winners and four wildcard teams (the top-ranked non-division-winners). The first round of the playoffs consists two wild-card games: single-game matches in which the four wild-card teams are reduced to two. The winners move on to the Divisional series with the six division winners for an eight-team, three-round tournament. Although this is billed as adding two extra "one-game showdowns" to the post-season, it could also be viewed as adding a fourth round to the ten-team tournament with six byes for the division winners. The FA Cup also has certain teams compete in up to 6 preliminary rounds to qualify for the first round "proper". Another example is the NCAA Basketball Tournament, which effectively grants 60 byes for its "play-in" round, as eight teams compete for the final four spots in the tournament, though the play-in round and all eight of those teams are officially part of the tournament.
"Bye" has a second meaning in sports like gridiron football, as both Canadian and American professional football leagues use the term "bye week" for any week during the regular season in which a team does not play a game. Each NFL team has one "bye week" during a normal season; this is placed on the team's schedule, usually falling between Week 5 and Week 11 inclusive. The NFL has used the bye week since 1990 so as to extend the 16-game regular season schedule to span 17 weeks. The 1993 NFL season spanned 18 weeks with each team having 2 bye weeks. In the rare case of a game postponement that cannot be made up within the week, a bye week may act as an available date to reschedule the delayed game, with the day of postponement acting as the new "bye week"; although both teams would have to be available on the same bye week; this was done during the 2008 NFL season when the Baltimore Ravens and the Houston Texans had to reschedule their Week 2 matchup in Houston due to Hurricane Ike, which also impacted the Cincinnati Bengals' schedule. Similarly, the Miami Dolphins and Tampa Bay Buccaneers were given a Week 1 bye week due to Hurricane Irma in the 2017 season.
During the 1960 and 1966 NFL seasons, the league had an odd number of teams due to expansion. Each week during those seasons, one team had a bye, including one team each in the first and last week of the season. (Thus, because they had to play all their games with no break in the middle, those two teams effectively had no byes.) The American Football League (at the time a completely separate league, but later became the American Football Conference) also had an odd number of teams in 1966 and 1967 following the addition of the Miami Dolphins, leaving each team with two bye weeks.
In the 1999 through 2001 seasons, the NFL had an odd number of teams, 31, as a result of the Cleveland Browns re-entering the league. Each week during these three seasons featured at least one team with its bye week (the 2001 season also added an additional impromptu league-wide bye the weekend after the September 11 attacks). The league returned to having an even number of teams (32) in the 2002 season with the addition of the Houston Texans, and implemented the current bye week system.
Sarcastically, the media may refer to a team having a "bye week" if that team is playing an especially bad team and is all but assured of a win, such as the 2008 Detroit Lions or just about any post-1999 Cleveland Browns game.
Traditionally, the CFL has had nine teams and required bye weeks. Each team has two bye weeks during the 20 week 18-game regular season. When the league had only 8 teams, the league usually had no bye weeks. However between 2007 and 2013, the league had one bye per team over in two weeks in August (4 teams would have a bye during week 6 and the other 4 teams would have a bye on week 7).
The Arena Football League has historically not used bye weeks. Other indoor American football leagues have typically been forced to incorporate irregular byes into their schedule due to the often unstable franchises in those leagues.
In Australia's National Rugby League (NRL), each team has two byes each season. During the representative period of the season (such as the State of Origin), byes are generally scheduled to the clubs that are expected to have the most players involved in the representative match, in the round preceding (or following) the representative fixture, to allow those clubs to sufficiently rest those players and prevent them from fielding a weakened side. On the competition ladder, teams are awarded two points (equivalent to a win) during their bye week except for the Melbourne Storm in 2010, who were barred from receiving premiership points for the remainder of the season as a punishment for gross long-term breaches of the salary cap.
The Australian Football League, which comprises an even number of clubs, gives each club a bye week in mid-season. In 1915, 1919 to 1924, 1942 and 1943, 1991 to 1994 and 2011, when there were an odd number of clubs competing, each club was given two byes.
In both leagues, and under many other professional and amateur sports leagues in Australia, higher placed teams don't earn byes during finals, but instead the opportunity not to be eliminated by losing their first-round match (also called a double chance). This practice is common in Australia, but it is not used in most other countries, to earn an easier passage to the Grand Final as reward for finishing higher on the ladder. This is different from a double elimination format, in which a team has to lose both in the tournament and the repechage to be eliminated.
In the Provincial Championships, a team may receive a bye. This is due to the irregular number of teams competing in each Championship. Thus the method used differs in each Provincial Championship.
For example, below is an assessment of the 2012 Provincial Championships, and their use of the "bye".
In the 2012 Connacht Senior Football Championship, a quarter-final was not played by Mayo. Mayo therefore advanced directly to the semi-final to await the winner of the game between Leitrim and London.
In the 2012 Ulster Senior Football Championship, all teams except Cavan and Donegal were permitted to advance to the quarter-finals without playing a game in the preliminary round. Cavan and Donegal played each other to determine which would join the other seven teams in the quarter-finals.
Connacht and Munster did not make use of a preliminary round, while Leinster and Ulster did.
In a Swiss-system tournament with an odd number of players, one player gets a bye in each round, but not all players will get a bye (as there are fewer rounds than there are players). However, as with the case of NFL "bye weeks", these "byes" do not confer any advantage, or in the case of a seeded tournament, that any player/team receiving one is perceived as any better than one that does not, as all of the participants receive one, whereas the awarding of a bye in a single-elimination tournament most definitely does, in both cases.