Major League Baseball (MLB) is the world’s premier baseball association and is based in North America, largely in the United States. The American League (AL) has used the modern 162-game format since 1961, and the National League (NL) adopted it the next year in 1962.

The Basics

MLB comprises two leagues: AL and NL, and each league comprises three divisions: East, Central, and West. Each division has 5 teams, which means there are 15 teams in each league and 30 in the MLB overall. All MLB teams play 13 games against divisional opponents for 52 games overall. They play 64 intraleague games, which are games in their league but outside their division. They also play 46 interleague games, which allows for regional rivalry matchups, such as the Mets vs. the Yankees and the White Sox vs. the Cubs.

The league office typically releases the official schedule in August of the year prior. Fans can generally count on those dates and times, but a 2026 media-rights deal allows for flex games. This is most noticeable with Sunday games, as NBC is able to flex games to the morning for its Sunday Leadoff broadcast and to the evening for its Sunday Night Baseball broadcast.

Interleague Play

The MLB began regular-season interleague play in 1997, breaking an over-100-year-old tradition of separate league schedules. The goal was to increase revenue through an emphasis on local rivalries. In 2023, MLB expanded the concept so that every team in the league plays one another at least once a year. The goal here was to increase exposure around the league to its star players. A core criticism is that it has diluted the divisional rivalries. Prior to the 2023 season, a team would play almost half its games (76 or more) within its own division.

Playoff Structure

The playoff structure has changed considerably over the years. From 1969 through 1993, only four teams made the playoffs. Beginning in 1994, MLB began expanding participation to the playoff structure we have today. The modern playoffs feature 12 teams, 6 from each league. Each league has three division winners and three wild-card teams. The top two division winners in each league receive a bye for the first round of the playoffs. The other eight teams participate in a best-of-three Wild Card Series. The Division Series for each league features the #1 seed vs. the #4/#5 winner and the #2 seed vs. the #3/#6 winner. The NL and AL Championships are best-of-seven matchups, and the World Series features the AL champ vs. the NL champ in a best-of-seven series.

Tiebreakers

For many years, MLB had a single-game tiebreaker rule that could result in a 163rd game for some teams. That’s no longer the case, as MLB transitioned entirely to mathematical tiebreakers with the 2023 season. MLB determines home-field advantage based on the teams’ overall records within their own leagues. To break ties for playoff spots, it uses the team’s head-to-head records, followed by their intra-division or inter-division records.

Collective Bargaining Agreement

MLB can make rule changes from season to season via the Joint Competition Committee, which does involve player input. The league cannot, however, make significant changes to the MLB season structure without updates to the collective bargaining agreement (CBA). The CBA is a legally binding contract between the MLB Players Association (MLBPA) and all 30 MLB clubs. The current CBA was signed ahead of the 2022 season and is set to expire after the 2026 season.

World Baseball Classic

The World Baseball Classic (WBC) is an international baseball tournament that occurs every four years. It involves many top-level MLB players but is held during March, coinciding with MLB’s spring training. During WBC years, the spring training season unfolds normally, and there’s no impact on the league’s regular season.

MLB at the Olympics

Baseball does not have a regular presence at the Olympics, but it will be featured as part of the 2028 Summer Games in Los Angeles. That tournament will take place from July 13 to July 19. While not finalized as of this writing, the MLB intends to allow its players to participate and may need to suspend the 2028 regular season during the tournament period to accommodate it.

Proposed Realignment

Current MLB commissioner Rob Manfred has spoken frequently about the league expansion and realignment he wants to achieve prior to leaving office. His goal is to transition from six five-team divisions to eight four-team divisions for a total of 32 clubs. One of the benefits of this approach for both the teams and players is that it would reduce travel time. The smaller divisions would also allow for more games between division opponents, hopefully restoring some of that rivalry drama that was lost with the move to 46 interleague games. A shorter schedule—somewhere between 154 and 156 games—is on the table as well, but there’s skepticism over whether Manfred can get most of the owners to agree to this change.

The Seasons Ahead

This is an exciting time for MLB, as the league has recently experienced some of the highest postseason viewership of all time. There’s also anxiety as the current CBA expires on December 1, 2026. Some industry insiders expect a lockout over growing salary concerns, and whatever the final agreement is, it’s likely to have a big effect on the MLB season structure going forward.