A LITTLE FOCUS. A FRESH START.
Play Diagonal Sudoku (Sudoku X)
Play Diagonal Sudoku, also called Sudoku X, free online. Solve both marked diagonals alongside the usual rows, columns, and boxes.
Get the iPhone app
OneStop Sudoku, wherever you go.
Website saves stay in this browser and don’t transfer to the app.
Scan to downloador tap to open
The game loads here. Choose a difficulty to start or resume a puzzle.
LEARN THE TWIST
How to play Diagonal Sudoku (Sudoku X)
Unlike Classic, both corner-to-corner diagonals must also contain 1–9 without repeats. Other, shorter diagonal lines have no special rule.
The rules
Fill each row, column, and 3×3 box with 1–9, without repeats. Both marked main diagonals also contain 1–9 without repeats. Also called Sudoku X.
A useful first move
Treat each marked diagonal like an extra row. Check its missing digits whenever a new number lands on it, especially in the center of the grid.
A 6 on the top-left to bottom-right diagonal rules out 6 in every other cell on that diagonal. The center cell belongs to both main diagonals, so a digit there constrains both.
Controls, difficulty, and saved games
Choose Beginner, Easy, Medium, Hard, or Expert above. Select an empty cell, then tap a number or use your keyboard. Notes let you pencil in candidates; three hints are available. Three mistakes end the puzzle.
Every mode and difficulty keeps a separate save in this browser. You can switch puzzles and return to your place. Clearing site data removes these saves; they do not sync with another device or the iPhone app. Settings include night mode and optional automatic cell advancement.
Correct entries earn points. High scores are stored by mode and difficulty and update only when beaten; completed-puzzle count and day streak are shared.
FIFTEEN WAYS TO PLAY
Explore all Sudoku modes
A familiar grid, a different kind of logic. Every mode is free to play in your browser.