X Sudoku 9×9 Medium — Set 99
Solver Notes
9x9 X-Sudoku at Medium difficulty. You will need hidden singles and basic elimination chains that leverage the diagonal constraint. 12-20 minutes.
X-Sudoku — Free Online & Printable
X-Sudoku adds a diagonal constraint to the classic sudoku rules. Both main diagonals — running from top-left to bottom-right and from top-right to bottom-left — must each contain the numbers 1 through 9 without repetition. This is the most accessible sudoku variant: the two extra constraints actually make many cells easier to deduce, since numbers on the diagonals are additionally restricted. If you''ve mastered standard sudoku and want a fresh twist without learning complex new rules, X-Sudoku (also called Diagonal Sudoku) is the ideal starting point.
About 9x9 Grid
The 9x9 grid is the full standard size for all sudoku variants. With 81 cells in 3x3 boxes, a 9x9 variant puzzle takes 10 to 60+ minutes depending on difficulty level and variant type. All variant rules reach their full expressive potential at this size: Killer cages create complex arithmetic networks, Jigsaw regions form visually distinctive shapes, and diagonal constraints span the entire grid. The 9x9 is where experienced solvers spend most of their time, and where the depth of each variant is fully revealed.
Medium Difficulty
Medium difficulty requires applying variant rules in combination with standard techniques. You''ll need hidden singles (where a number can only go in one cell within a region, even if multiple numbers are possible for that cell) and basic elimination chains. For Killer Medium, expect some cage combinations where two or more possible sets remain and must be narrowed by row/column logic. Average time: 10-20 minutes for 9x9. Candidate notation is helpful but not essential.
How to Get Started
- Choose "New Puzzle" to generate a fresh puzzle with a unique solution
- Click or tap cells to enter numbers (1-9 for 9x9)
- Use the constraint highlights to track which numbers are still available
- Print the puzzle if you prefer solving on paper