Mittens is a chess engine developed by Chess.com and was released on January 1, 2023 as part of a new year’s event. It was one of five cat-themed engines released, and became popular in the chess community due to exposure through content made by chess streamers and a social media marketing campaign. The engine was conceptualized by Will Whalen, a college student at Hamilton College, and has a unique “personality” that trash talks opponents using quotes from various historical figures. The software used to run the engine has not been disclosed by Chess.com, but it is speculated to be based on Komodo Dragon 3.
Mittens’ strategy is to slowly grind down opponents, similar to the playing style of Anatoly Karpov. The engine has an official ELO rating of one on Chess.com, however, it is believed to have a true rating of between 3200 to 3500 due to its ability to beat or draw against many top human players. It was also found to have an upper bound of 3700 after playing against Stockfish 15, but lost the two games played.
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Mittens, a chess engine developed by Chess.com, has an ELO rating of one on the website. However, despite this low rating, the engine’s playing style and tactics suggest that it is much stronger. It has been able to beat or draw against many top human players, with estimates of its true rating ranging from 3200 to 3500. This was confirmed when it played against Stockfish 15, a 3700 rated engine, and lost both games. Against human players, Mittens has won 99% of the multiple millions of games it has played, with top players such as Hikaru Nakamura, Benjamin Bok, and Eric Rosen struggling against it.
Mittens also participated in Chess.com’s Computer Chess Championships as a side act and won against an engine inspired by the film M3GAN. It became popular with the chess community due to its concept and design, helped by social media exposure created by Chess.com. Chess streamers like Rozman and Nakamura contributed to this by creating content around the engine. The popularity of Mittens led to record levels of traffic on Chess.com, causing issues with database scaling and leading the website to upgrade their servers and invest more in cloud computing to solve these problems.