Matches consisted of two games. Players had 90 minutes for the first 40 moves followed by 30 minutes for the rest of the game with an addition of 30 seconds per move from move one. If the match was tied after the regular games, tie breaks were played on the next day. The format for the tie breaks was as follows:
Four rapid games were played. According to chess journalist Mig Greengard, a "high FIDE official" admitted off the record that this unusual decision of playing four games instead of two was actually a mistake that was spotted too late to correct it.
If the score was still tied, up to five pairs of blitz games were played. If one player led after a pair of blitz games, that player was declared the winner. This was a change from previous events, for instance at the Chess World Cup 2007 the match went to an armageddon game after a single pair of blitz games.
If the score was still tied after five pairs of blitz games, a single armageddon game would be played. White had 5 minutes, black had 4 minutes, and both players had three-second increments beginning with move 61. Ultimately, no Armageddon games were played, as all matches were decided before that stage.
All players are grandmasters unless indicated otherwise. The pairings of the 1st round were announced on 2 November 2009, immediately after the publishing of the November rating list. The list of players who declined participation: Anand, Carlsen, Topalov, Aronian, Kramnik, Leko, Adams, Nakamura, and Ni Hua. Among them, Anand, Topalov and Aronian had already qualified for the Candidates or the Championship match; Carlsen, Kramnik, Nakamura, Adams and Ni had committed to play in the London Chess Classic on 7–15 December 2009. Qualification paths:
In the first round of the tournament all of the top 30 seeded players progressed, with the sole exception of Slovakian Sergei Movsesian, who was eliminated by the Chinese 113th seed Yu Yangyi. Judit Polgár achieved a walkover, due to her opponent Duško Pavasovič withdrawing from the competition due to injury. The round was notable for the 16-game match between Pavel Tregubov and Varuzhan Akobian: after each winning with white over the first two days, their tiebreak held a marathon of four rapid games followed by ten blitz games. The two players fought until near 1 a.m. local time for the right to face Ruslan Ponomariov in the second round, Akobian finally achieving the decisive two-point advantage in the final bout before an Armageddon game would have been required.
Round two
The first day of Round Two included a number of upsets. The highest seed to have won their match was Alexander Grischuk, as Peter Svidler, Alexander Morozevich, Teimour Radjabov and Vassily Ivanchukall lost and the remaining highest seeds drew. On the next day of matches, Morozevich, Radjabov and Ivanchuk were all eliminated, and exactly half of the matches went to tie-breaks. Of the 32 players to reach Round Three, all but seven players had been originally seeded in the top 32.
Round three
Sixteen-year-old Wesley So, who had upset Ivanchuk in Round Two, achieved another major upset, defeating Gata Kamsky, the 2007 winner, 1½-½. In the second rapid tiebreak, Chinese players Wang Yue and Li Chao were not at their seats for the start of the round, and lost the game, and their matches against Bacrot and Gashimov.
Round four
This round marked the departure of most of the youthful players from the World Cup. Wesley So, Fabiano Caruana and Maxime Vachier-Lagrave were eliminated by the more experienced Malakhov, Gashimov and Gelfand respectively, leaving Sergey Karjakin the only under-20 player left in contention.
