🟢 How to play Whisper Sudoku (German Whispers)

By Miguel Arechaga

Whisper Sudoku, known as German Whispers, is a very popular "line" variant in modern puzzles and on channels like Cracking the Cryptic. Green lines are drawn on the board, and the rule is curious: neighboring numbers on the line must be "far apart," differing by at least 5. Here are the rules and a few tips.

What is Whisper Sudoku?

It's a standard 9x9 sudoku with one or more green lines drawn on it. Along each line, two consecutive cells must differ by 5 or more. For example, a 1 can sit next to a 6, 7, 8 or 9; a 2 next to a 7, 8 or 9, and so on. The name "German" comes from the community that popularized the variant.

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. On each green line, the difference between two neighboring cells must be 5 or greater.
3. You start with some clue cells and fill in the rest with logic. Every puzzle has a unique solution.

Tips to solve Whisper Sudoku

• The 5 is problematic: since it would need a neighbor differing by 5 (a 0 or a 10, neither of which exist), the 5 almost never appears in the middle of a whisper line. That's a powerful clue.
• Low and high numbers alternate: lines tend to bounce between the low group (1-4) and the high group (6-9). Spotting that pattern helps a lot.
• The extremes 1 and 9 are very flexible (1 allows 6,7,8,9 and 9 allows 1,2,3,4), so they reveal less information; start with more restricted cells.
• Combine the line rule with the classic elimination techniques of sudoku.

How it differs from regular sudoku

Compared to classic sudoku, Whisper imposes "distance" relationships between neighboring cells on a line, the opposite of Renban Sudoku (which wants them close together). If you enjoy line-based variants, you'll also enjoy Thermometer Sudoku.