QSudoku is a logic-based number placement puzzle. The objective is to fill a 9?9 grid so that each column, each row, and each of the nine 3?3 boxes (also called blocks or regions) contain the digits from 1 to 9, only one time each (that is, exclusively). The puzzle setter provides a partially completed grid.

The modern puzzle was invented by an American architect, Howard Garns, in 1979 and published by Dell Magazines under the name "Number Place".It became popular in Japan in 1986, after it was published by Nikoli and given the name Sudoku, meaning single number. It became an international hit in 2005.

The word sudoku derives from the Japanese phrase "Suji wa dokushin ni kagiru," meaning "the numbers must be single," or "the numbers must occur only once."

The attraction of the puzzle is that the rules are simple, yet the line of reasoning required solving the puzzle may be complex. The level of difficulty can be selected to suit the audience as Low, Medium and High.