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UPK is an acronym for Unfair Prior Knowledge. This refers to any information about a board not given directly by squares being opened for the first time. The concept developed in response to players who had used knowledge of Board Cycles to play games multiple times, in particular to set records on the Dreamboard. UPK is banned from the World Ranking.


The idea of UPK had been discussed many times before the term was invented. The incident leading to its creation occured on 21 May 2004 when Stephen Arnason (Canada) broke his Intermediate record of 15 seconds with a score of 11 seconds on the Dreamboard. The founder of the Bestever ranking, Georgi Kermekchiev (Bulgaria) announced the following day in the Guestbook that it would not be accepted. He suggested only Clone be used for sub15 games and asked for opinions.

Stephen wanted to know why his score was rejected when other Dreamboard scores had been allowed on the ranking. He added that the Dreamboard was only one of many boards that people recognised and should not be singled out. If the Dreamboard was banned, then all Winmine games should be banned. Stephan Bechtel (Germany) replied that it was only boards played using "Prior Knowledge" that should be banned. James Custer (USA) added that the Dreamboard itself was not a problem, rather it was "Pre-Knowledge" being used to solve the Dreamboard. However, he believed memorising entire boards was equivalent to memorising patterns.

Daniel Lynch (Ireland) entered the dicussion on 22 May 2004 and said, "I think different people have different ideas of what constitutes 'fair sweeping'. Some think that it's unfair to have knowledge of the next board. Others think that it's unfair to have knowledge of the possibility of the next board." He continued, "For me, fair sweeping entails no knowledge of the next board and no knowledge of the possibility of the next board. Purely personal though these feelings are, I imagine this is what the game was originally intended to be like. It seems clear that our problem with the cycles is not limited to just the DB. Players have knowledge of other boards, besides the DB, and can use their experience to lower their times, purely on the basis of having played a particular board previously. This, for me (though clearly not for others), is not what minesweeper is about."

The debate continued strongly for several days, so Gergely Nagy (Hungary) created a poll in Minesweeper Addicts on 25 May 2004. In this poll one of his options was to erase any "unfair-prior-knowledge" games from the rankings. Later that day, Dave Matson (Canada) referred to the poll in the Guestbook using the abbreviation "UPK" for the first time.


  • UPK — Rodrigo Camargo wrote the first definition of UPK on 09 June 2004