Free online anti-knight sudoku — medium difficulty
Anti-Knight Sudoku follows all standard Sudoku rules, plus one extra constraint: no two identical digits can be a chess knight's move apart (an L-shape: 2 squares in one direction + 1 square perpendicular).
In the diagram above, if the center cell contains a 5, then none of the red cells can also contain a 5.
Ready for the next step? Medium Anti-Knight Sudoku puzzles offer a satisfying challenge for players who have mastered the basics. With approximately 33 given digits, these puzzles require you to actively combine standard Sudoku elimination with knight-move logic to progress.
At medium difficulty, you'll find that the knight constraint becomes an essential tool rather than just a bonus hint. Many cells will be ambiguous using only row, column, and box logic — but the knight constraint provides just enough extra information to crack them. This is where Anti-Knight Sudoku really shines as a puzzle format.
Use pencil marks (notes mode) to track candidate digits in each cell. When you eliminate a candidate due to the knight rule, mentally trace the L-shape to confirm. Look for "hidden singles" — cells where a digit has only one valid position when you account for all constraints including knight moves. If you find medium too easy, step up to hard Anti-Knight Sudoku.
The more medium Anti-Knight Sudoku puzzles you solve, the faster you'll recognize knight-move patterns. Your pattern recognition will improve, and soon you'll spot knight conflicts at a glance. If you're still building confidence, try our easy Anti-Knight Sudoku puzzles first.