Sudoku variants are alternative versions of the traditional Sudoku puzzle, which typically consists of a 9x9 grid divided into nine 3x3 subgrids. These variants introduce new rules or grid shapes, adding complexity and variety to the gameplay. Examples include Killer Sudoku, where players must also consider the sums of numbers in outlined regions, and X-Sudoku, which requires that the numbers along the diagonals also contain unique digits. Other popular variants include Hyper Sudoku, featuring additional regions that must contain unique numbers, and Jigsaw Sudoku, where the subgrids are irregular shapes. These variants cater to different skill levels and preferences, making Sudoku an engaging puzzle for a wider audience.