Editing World Chess Championship (section)

==Format==
Until 1948, world championship contests were arranged privately between the players. As a result, the players also had to arrange the funding, in the form of stakes provided by enthusiasts who wished to bet on one of the players. In the early 20th century this was sometimes an obstacle that prevented or delayed challenges for the title. Between 1888 and 1948 various difficulties that arose in match negotiations led players to try to define agreed rules for matches, including the frequency of matches, how much or how little say the champion had in the conditions for a title match and what the stakes and division of the purse should be. However these attempts were unsuccessful in practice, as the same issues continued to delay or prevent challenges. There was an attempt by an external organization to manage the world championship from 1887 to 1889, but this experiment was not repeated until 1948.

After the death of world champion [[Alexander Alekhine]] in 1946, the [[World Chess Championship 1948]] was a one-off tournament to decide a new world champion.

Since 1948, the world championship has mainly operated on a two or three-year cycle, with four stages:

# Zonal tournaments: different regional tournaments to qualify for the following stage. Qualifiers from zonals play in the [[Interzonal]] (up to 1993), knockout world championship ([[FIDE World Chess Championships (1998–2004)|1998 to 2004]]) or [[Chess World Cup]] (since 2005).
# Candidates qualification tournaments. From 1948 to 1993, the only such tournament was the [[Interzonal]]. Since 2005, the Interzonal has mainly been replaced by the [[Chess World Cup]]. However extra qualification events have also been added: the [[FIDE Grand Prix]], a series of tournaments restricted to the top 20 or so players in the world; and the [[FIDE Grand Swiss Tournament 2019|Grand Swiss]] tournament. Since 2023, the Grand Prix has been replaced by the FIDE Circuit, making many more tournaments (besides those organised by FIDE) contribute towards Candidates qualification. In addition, a small number of players sometimes qualify directly for the Candidates either by finishing highly in the previous cycle, on [[Elo rating system|rating]], or as a [[Wild card (sports)|wild card]].
# The [[Candidates Tournament]] is a tournament to choose the challenger. Over the years it has varied in size (between 8 and 16 players) and in format (a tournament, a set of matches, or a combination of the two). Since the [[World Chess Championship 2013|2013 cycle]] it has always been an eight-player, double round-robin tournament.
# The championship match between the champion and the challenger.

There have been a few exceptions to this system:
* In the [[World Chess Championship 1957|1957]] and [[World Chess Championship 1960|1960]] cycles, a rule existed which allowed the champion a rematch if he lost the championship match, leading to the [[World Chess Championship 1958|1958]] and [[World Chess Championship 1961|1961]] matches. There were also one-off rematches in [[World Chess Championship 1986|1986]] and [[World Chess Championship 2008|2008]].
* The [[World Chess Championship 1975|1975]] world championship was not held, as the champion (Fischer) refused to defend his title; his challenger (Karpov) became champion by default.
* There were many variations during the world title split between 1993 and 2006. FIDE determined the championship by a single knockout tournament between [[FIDE World Chess Championships (1998–2004)|1998 and 2004]], and by an eight-player tournament in [[FIDE World Chess Championship 2005|2005]]; meanwhile, the Classical world championship had no qualifying stages in [[Classical World Chess Championship 2000|2000]], and only a Candidates tournament in its [[Classical World Chess Championship 2004|2004]] cycle.
* A one-off match to reunite the world championship was held in [[FIDE World Chess Championship 2006|2006]].
* The [[FIDE World Chess Championship 2007|2007]] world championship was determined by an eight-player tournament instead of a match.
* The [[World Chess Championship 2023|2023]] world championship was played between the top two finishers of the Candidates, as the champion (Carlsen) refused to defend his title