How to Play German Whispers
Adjacent digits on the green line must differ by at least 5
The Rules
Standard Sudoku rules apply: fill every row, column, and 3×3 box with the digits 1–9, each appearing exactly once.
German Whispers (also known as Whisper Sudoku) draws green lines on the grid. Any two digits that are adjacent on the line must differ by at least 5. Because the minimum difference is 5 and digits range from 1–9, this creates a strong alternating high-low pattern: if one cell is low (1–4), the next must be high (6–9) and vice versa. The line constraint eliminates 5 as a valid digit in most positions.
At a Glance
How to Solve German Whispers
Common Questions
What is German Whispers Sudoku? ▾
German Whispers Sudoku is a variant where green lines are drawn across the grid. Any two cells adjacent along a green line must contain digits that differ by at least 5. Standard Sudoku rules apply — every row, column, and 3×3 box must contain 1–9 exactly once.
Why is it called German Whispers? ▾
The name comes from the puzzle community and refers to a variant popularised in German puzzle circles, with 'whispers' evoking the idea of information passing along a line with a significant minimum separation at each step.
What digits can sit next to each other on a whisper line? ▾
Only pairs with a difference of 5 or more: 1&6, 1&7, 1&8, 1&9, 2&7, 2&8, 2&9, 3&8, 3&9, 4&9. This means whisper cells must alternate between the low group (1–4) and high group (6–9). Digit 5 cannot appear on any whisper line.
What is the best first move in German Whispers Sudoku? ▾
Identify the longest whisper lines and mark each cell as low (1–4) or high (6–9) based on alternation. Any whisper cell in a row, column, or box where the low or high group is almost fully placed gives you a direct elimination or placement.
Is German Whispers Sudoku hard to learn? ▾
The constraint is simple to understand but its consequences take practice to apply automatically. The forced high-low alternation is the key insight — once you internalise it, you can immediately split each line cell into one of two groups and halve your candidate list from the start.
How long does German Whispers Sudoku take to solve? ▾
Easy puzzles take 8–18 minutes. Medium puzzles run 18–35 minutes. Hard and expert puzzles can take 45 minutes to well over an hour. Longer whisper lines spanning the full grid are the most time-consuming because they interact with almost every row, column, and box simultaneously.