🐴 How to play Anti-Knight Sudoku

By Miguel Arechaga

Anti-Knight Sudoku is a variant that's become very popular thanks to puzzle channels like Cracking the Cryptic. It adds a restriction borrowed from chess: two cells a knight's move apart can't share a number. It's an easy rule to state, but it opens up plenty of new deductions. Here's how to play and a few tips.

What is Anti-Knight Sudoku?

It's a standard 9x9 sudoku with the chess knight restriction added: from any cell, the cells a knight would reach (an L-shaped move: two in one direction and one perpendicular) can't contain the same number. All the other sudoku rules stay the same.

Rules and how to play step by step

1. The sudoku rules apply: 1 to 9 without repeats in each row, column and 3x3 box.
2. In addition, two cells a knight's move apart (L-shaped) can't hold the same number.
3. You start with some clue cells and fill in the rest with logic. Every puzzle has a unique solution.

Tips to solve Anti-Knight Sudoku

• Think of the eight knight cells: when you place a number, mentally mark the (up to eight) knight's-move cells; none of them can repeat that number.
• Combine with box and line: the knight restriction often eliminates the last candidate that the box or row hadn't already ruled out.
• Repeated numbers in adjacent diagonal boxes benefit the most from this rule; keep an eye on those zones.
• Lean on the classic elimination techniques and add the knight rule as one more layer.

How it differs from regular sudoku

Compared to classic sudoku, Anti-Knight introduces relationships between cells that are far apart from each other, not just in the same row, column or box. That forces you to look at the board differently. If you like variants with extra restrictions, you'll also enjoy other sudoku variants and a rundown of the best-known ones.