The Major League Baseball postseason is an elimination tournament held after the conclusion of the Major League Baseball (MLB) regular season. Since 2012, the playoffs for each league--American and National--consist of a one-game wild-card playoff between two wild card teams, four best-of-five Division Series (LDS) featuring the wild-card winner and the winner of each division, and finally the best-of-seven League Championship Series (LCS). The winners of the American League Championship Series (ALCS) and the National League Championship Series (NLCS) play each other in the best-of-seven World Series. The current system allows for a maximum of 43 postseason games and a minimum of 26 games.
Major League Baseball is the oldest of America's major professional sports organizations, steeped in tradition with roots dating back to the 1870s. The final series to determine its champion has been called the "World Series" (originally "World's Championship Series" and then "World's Series") as far back as the National League's contests with the American Association starting at the beginning of the 1880s.
From 1901 to 1968, the American and National League teams with the best win-loss records in their respective leagues would win their league's championship, or pennant. In 1903, modern annual postseason play began with a one-round system, in which the American League champion would play the National League champion in a best-of-seven series (in 1903, 1919, 1920, and 1921 it was best-of-nine) called the World Series; however, there was no 1904 Series because the National League champion New York Giants refused to play. This single-tiered approach persisted through 1968, even with the expansions of 1961-1962 that expanded both leagues to 10 teams.
In 1969, both leagues expanded to twelve teams, which made it more difficult to compete for a league championship because there were more teams competing for the AL and NL pennants. In addition, a team would play other clubs in its own region of the country more than clubs in the rest of the country, creating an unbalanced schedule that in some years could give a team from one region an advantage in fighting for a single pennant. To remedy this, and imitating the other major sports' long-standing playoff traditions, Major League Baseball split each league into Eastern and Western divisions, creating four divisions overall and no worse than a sixth-place finish for any team in any division until later expansions in 1977 and 1993. This created a new postseason round called the League Championship Series (LCS), in which the Eastern and Western division champions of each league would play a best-of-five series to determine the league champion. In 1985 the LCS was expanded to a best-of-seven series.
Under this system, it was possible for one of the best teams in a league to be left out of the postseason if it failed to win its division. Most notably, in 1993, the Atlanta Braves and San Francisco Giants finished with the two best records in the majors, with 104 and 103 wins, respectively. However, since both teams played in the National League West division, the Giants missed the postseason by a single game.
The baseball players' strike of 1981 uniquely--for this era--added another round to the postseason. Because the strike split the season into two roughly equal halves, the division winners of each half of the 1981 season first met in a best-of-five Division Series. The winners of the division series then progressed to the league championship series, with the remainder of the postseason following a similar format to other years in this era.
Major League Baseball went through a realignment in 1994, when both the American and National Leagues expanded to three divisions: Eastern, Central, and Western. To avoid a playoff with an odd number of divisional winners, the league added a wild card playoff spot to each league, imitating the original post-merger NFL system. The wild-card for each league would be the team with the best record that did not win its division, eliminating a circumstance where a team with the second-best record in the entire league would miss the playoff because of not winning its division. This new format doubled the postseason contenders in each league from two to four, and from four teams overall to eight. The addition of a second wild card spot occurred in 2012.
The additional teams meant another elimination round was necessary. This new round would become the new first round of the postseason, the best-of-five Division Series. This term had first been used for the extra round required in 1981 due to the "split-season" scheduling anomaly following the midseason baseball players strike. This format was in place for the 1994 season, but that year's players' strike canceled the postseason. The format was realized on the field in 1995.
Under this format, in the two Divisional Series, the wild card team played the divisional champion outside its own division that had the better record, with the remaining two teams playing each other in the second Division Series for each league. The two Division Series winners from each league go on to play each other in the League Championship Series. As with the previous postseason format, the winners of each League Championship Series met in the World Series.
With the adoption of the new collective bargaining agreement in November 2011, baseball commissioner Bud Selig announced that a new playoff system would begin within two years; the change was ultimately put into place in 2012. The format chosen was the one-game wild-card playoff.
Under this format, a second wild card team has been added to each league, i.e., the team with the second-highest win total in each league among non-division winners. The two wild card teams play in a one-game playoff after the end of the regular season, with the winner advancing to the Division Series. The divisional champions qualify for the Division Series just as in the previous format; however, under the expanded wild card format the winner of the one-game wild card playoff faces the top-seeded divisional champion in the Division Series, regardless of whether the two teams are in the same division, while the second- and third-seeded divisional champions play each other in the other Division Series. The format for placement in the League Championship Series and World Series remains.
MLB is proposing to expand the playoffs to 14 teams; once the current collective bargaining agreement expires in 2021, the change may happen in 2022. There could be four wild card teams & three division winners per league. Only the division winner with the best record gets a first-round bye into the Division Series.
The proposed first-round format will be best-of-three series, with the higher seeds hosting every game. The second seed may choose to play the fifth, sixth or seventh-seeded team; then the third seed from remaining two; with the fourth playing the remaining team. No changes will be made for the rest of the playoffs. By default, the second hosts the seventh, the third hosts the sixth & the fourth the fifth.
During the suspension of the 2020 MLB season due to the COVID-19 pandemic, all proposals put forward during negotiations between the MLB and Major League Baseball Players Association (MLBPA) included a temporarily expanded postseason. The various proposals included 16-team formats and included the 2020 and (in some proposals) 2021 seasons. However, the eventual lack of a negotiated season structure initially resulted in the 2020 season being intended to use with the 10-team format.
On July 23, 2020, MLBPA and the owners agreed to expand to a 16 team playoff structure for the 2020 season. The round will be called the Wild Card Series. The format will consist of eight teams from each league, seeded in the following order: division winners by record (1-3), runner-up teams by record (4-6), and the two best teams remaining (7-8). All games in this format will be best of three, and will be played at the home ballparks of the higher seeds. All other series (LDS, LCS, and World Series) will remain as is. The WCS pairings will be as follows: top seed vs. eighth, second vs. seventh, third vs. sixth, and fourth vs. fifth. The DS will have the 1-8 winner play the 4-5 winner, while the 2-7 winner plays the 3-6 winner.
The World Series used several different formats in its early years. Initially it generally followed an alternating home-and-away pattern, except that if a seventh game was possible, its site was determined by coin toss prior to the sixth game. In 1924 the Series began using a 2-3-2 format, presumably to save on travel costs, a pattern that has continued to this day with the exception of a couple of the World War II years when wartime travel restrictions compelled a 3-4 format (used in 1943 and 1945, but not in the 1944 series, which was contested between crosstown rivals the St. Louis Browns and St. Louis Cardinals; all games were held in the same stadium in St. Louis). From the start of the 2-3-2 format through the 2002 season, home-field advantage generally alternated between leagues each year. Prior to the 1994 strike, the National League champion received home-field advantage in even-numbered years and the American League champion in odd-numbered years; these were reversed for 1995-2002 (because 1994 would have been the NL's turn to have home-field, but the World Series was cancelled by the aforementioned strike). That changed starting in 2003.
The 2002 All-Star Game had ended in a tie, much to the displeasure of both fans and sportswriters who complained about a lack of intensity and competitiveness on the part of the players. This hit especially close to home for Commissioner Bud Selig, as the game had been played in his home city of Milwaukee, Wisconsin. In response, to give some real meaning to the game, in 2003 MLB began assigning home-field advantage in the World Series to the winner of that year's All-Star Game, which is typically held in mid-July.
Following the acceptance of a new collective bargaining agreement after the 2016 season, home-field advantage in the World Series is no longer tied to the outcome of the All-Star Game, but instead goes to the team with the better regular-season record. One exception is 2020, when it will be played at a neutral site for all those games.
Until 1998, the LCS alternated home-field advantage with a 2-3 format in the best-of-5 era (1969-84) and a 2-3-2 format when it went to best-of-7 (1985-present). Since 1998, the team with the better record has had home field advantage, but a wild card team can never secure the extra home game, regardless of regular-season records.
Until 1997, the Division Series rotated in which one of the three division-winning teams did not have home field-advantage, with the wild card team never having it. Since 1998, the two division winners with the best records in each league have home field, with the least-winning divisional winner and the wild card do not have home field. The Division Series used a 2-3 format until 1998 and now uses a 2-2-1 format. This is seen as a more fair distribution of home-field advantage because previously under the 2-3 format, the team hosting the first two games had absolutely no chance of winning the series at home. With the current 2-2-1 format however, both teams have the home-field advantage in a sense. While one team gets to host three games (including the critical first and last game), the other team does get two chances out of three (games 3 and 4) of winning the series on its home field.
With the adoption of the expanded playoff format in 2012, the five-game Division Series began with two home games for the lower seeds, followed by up to three home games for the higher seeds. This one-year change eliminated a travel day prior to a decisive Game 5 of a Division Series and was necessary because the 2012 regular-season schedule was announced before the agreement on the new postseason was reached. Since 2013, the Division Series restored the 2-2-1 format.
Before 2012, the Wild Card team played the team with the best record that was not from their division. With the addition of a second Wild Card team the Wild Card Game was created. The Wild Card Game is a one-game playoff to determine who advances to the next round of the playoffs to take on the team with the best overall record in their respective league. The 4th seeded team or 1st Wild Card hosts the 5th seeded or 2nd Wild Card. This has caused some controversy in that some people want a three-game series to determine a winner instead of an elimination game to make the playoffs more fair.  The 2020 implementation of the Wild Card Series will have all three games hosted at the higher seed, to reduce travel and to reward regular season performance.
There are three factors that determine the actual amount of bonus money paid to any individual player: (1) the size of the bonus pool; (2) their team's success in the season/post-season; and (3) the share of the pool assigned to the individual player.
There is a separate pool for each series - the Wild Card games, the Division Series, the League Championship Series, and the World Series. The players' bonus pool is funded with 60% of the gate receipts for each of the Wild Card games, the first three games of each Division Series, the first four games of each LCS and the first four games of the World Series; limiting the funding for the pool to these games, the minimum number in each series, removes incentive to extend the series for merely fiscal sake. The value of the gate is determined by the size of the venues, the amount of high-priced premium seating in the venues, the number of games played in the series and whether the games sell out. Ticket prices for each series are set by MLB, not the home teams, so they are relatively uniform across baseball.
The World Series winner gets 36%, the World Series loser gets 24%, both League Championship Series losers get 12%, the four Division Series losers get 3.25%, and the two Wild Card playoff losers get 1.5%. In 2020, the eight Wild Card Series losers got 0.375%.
The division of the team's share of the pool is voted upon by the players who have been on the team during the entire regular season, in a meeting chaired by their union representative. This meeting follows the trade deadline on July 31. Players who have been with the team for the full season automatically receive a full share. At the meeting, the full-season players vote on whether anyone else--including players who have not been with the team for the full season, coaches, and trainers--is to be granted a full share, less than a full share, a cash award, or no share. After the World Series, the pool of money is split according to the shares determined in the vote. There is no limit to the number of shares that may be granted, but a greater number of shares dilutes the value of each share, and consequently the amount each player is awarded.
Games 1, 2, 6 and 7 shall be scheduled in the ballpark of the opponent of a Wild Card Club in the League Championship Series, notwithstanding the percentage of games won and lost by such Wild Card Club