Carlsen, a Norwegian grandmaster, then staged a protest of Niemann by withdrawing from a rematch after playing just one move. Late last month, Carlsen gave voice to his actions and accused Niemann of having “cheated more — and more recently — than he has publicly admitted.” Tuesday’s report from Chess.com, which bills itself as “the No. 1 platform for online chess,” added some backing to Carlsen’s unspecific accusations.

Pointing to its “best-in-class” cheating-detection system, the website claimed Niemann “likely cheated” in more than 100 online games, including some that occurred after he had turned 17 and took place in prize-money events.

In chess, a long history of cheating, chicanery and Cold War shenanigans

At the same time, Chess.com said its investigation failed to turn up an abundance of “concrete statistical evidence” that Niemann cheated in his over-the-board (i.e., in-person) win over Carlsen or in a number of other OTB games. However, the site added that it found “suspicious” certain aspects of that victory, which broke Carlsen’s 53-game OTB winning streak despite Niemann playing from the slightly disadvantageous black position and noted his “statistically extraordinary” rise in the sport.

Niemann has not publicly commented on the Chess.com findings, which were first reported by the Wall Street Journal on Tuesday. He is set to compete in the U.S. Chess Championships beginning Wednesday in St. Louis. Officials with the Saint Louis Chess Club, which is hosting the OTB tournament, did not specifically address Niemann in response to a request for comment but expressed the club’s commitment to preventing cheating more generally.

“We take great pride in being able to host the top chess players from across the world at the Saint Louis Chess Club,” executive director Tony Rich said in a statement Wednesday morning. “As with all events, it’s imperative that we maintain high standards for fair tournament play. We always have — and will continue — to implement extensive anti-cheating measures.

“As we prepare for the upcoming U.S. Chess and U.S. Women’s Chess Championships, we anticipate hosting another successful event, complete with rigorous protocols to ensure the best chess players in the country can continue to compete on an even playing field.”

Jenkins: When chess is hard and cheating is easy, the next move is complicated

Chess.com said it removed Niemann from its platform and disinvited him from a major competition it is staging. The site said it dealt with him confidentially, keeping with its regular policy, and only began to make public statements on his situation after he spoke about their dealings. Niemann served an earlier suspension from the site and admitted to cheating, Chess.com said, after its “cheating-detection software and team uncovered suspicious play” at that time.

“We believe Hans is an incredibly strong player and a talented individual,” Chess.com stated in its report. “That said, given his history on our site, we did not believe we could ensure that he would play fairly in our online events until we could re-evaluate the evidence and our protocols. Nevertheless, and to be clear, it is not our position that Hans should be limited or banned from OTB chess.”

The International Chess Federation (FIDE), the sport’s governing body, announced in late September that it was launching an investigation of Carlsen’s accusations of cheating and Niemann’s comments on the matter. FIDE said its probe would be led by members of its Fair Play Commission and would include “the possibility to call for a consultation with external experts wherever analysis is required.” Chess.com indicated it was prepared to cooperate with FIDE’s investigation should it be asked to do so.

Cheating by a chess player, particularly in an online game, probably would involve connecting to a chess computer, or engine, capable of playing at a higher level than any human has been able to attain.

“Most chess engines use neural nets which have been trained on millions of top level chess games to capture the deepest of chess strategic understanding,” Chess.com noted. “They also have nearly infallible tactical calculation, as they can look more than 40+ moves deep into the position and calculate potential outcomes.”

Niemann has been alleged to have used such an engine in OTB matches, although his means of possibly doing so remain in the realm of speculation.

Carlsen said that during his loss last month, he “had the impression that [Niemann] wasn’t tense or even fully concentrating on the game in critical positions, while outplaying me as black in a way I think only a handful of players can do.”

Arousing suspicion from others was Niemann’s adroit counter after Carlsen made a relatively unusual opening. Niemann said afterward that “by some miracle” he had looked into the possibility of that sequence earlier in the day, adding, “It’s so ridiculous that I checked it.”

In its report, Chess.com pointed to other postgame comments by Niemann, in which he proposed a move that could have been made and then requested to see an engine’s evaluation of the move.

“This analysis and dependence on the engine,” the report stated, “seem to be at odds with the level of preparation that Hans claimed was at play in the game and the level of analysis needed to defeat the World Chess Champion.”

Chess.com claimed its cheating-detection system — which uses comparisons to both engine-recommended moves and a given player’s competitive profile, as well as input from “a panel of trained analysts” — had led to confessions of wrongdoing from four players in the FIDE top 100. In addition, the system was said to have resulted in the closure of online accounts of “dozens” of grandmasters, plus those of hundreds of other notable players.

The site reiterated that it was “unaware of any concrete evidence proving that Hans is cheating over the board or has ever cheated over the board.” Chess.com added that while some of Niemann’s recent online play appeared suspicious, it was not aware of evidence that he had cheated after August 2020. Chess.com also downplayed the possibility of widespread cheating on its platform, saying it estimated fewer than 0.14 percent of its users engage in such behavior.

“Our events are by and large free from cheating,” Chess.com said in the report. “We firmly believe that cheating in chess is rare, preventable, and much less pervasive than is currently being portrayed in the media.”