Hard Sudoku
Hard puzzles ask you to see three cells acting together. They reward neat notes and patience.
Hard Sudoku puzzles need naked triples or hidden triples: three cells that share three candidates, or three digits that fit in only three cells of a unit. Everything easier still applies, so keep all your techniques ready.
How to use the board
- Tap a cell, then a digit. On a keyboard, use 1 to 9, Backspace to erase and the arrow keys to move.
- Turn Notes on to write small candidate digits. Press N on a keyboard.
- Hint finds a naked or hidden single and tells you which one it is.
- Your game is saved in this browser. Nothing is sent anywhere.
What Hard means here
A Hard puzzle cannot be finished with singles, pairs, pointing pairs or box-line reduction alone. At some point you must find a naked triple or a hidden triple. The rest of the solve is usually easier once that move is made.
How to find triples
- Look at one unit at a time (a row, column or box) and list the cells with two or three candidates.
- For a naked triple, three cells together use only three different digits.
- For a hidden triple, three digits appear in only three cells of the unit, whatever else those cells hold.
- Remember: triples are often partial. A cell in a naked triple can hold just two of the three digits.
Habits that help
Keep notes tidy and complete. Work unit by unit rather than jumping around. When you are stuck, use the solver in step-by-step mode to see which pattern you missed. Then try Expert when Hard feels routine.
Frequently asked questions
Which techniques does Hard use?
Naked triples and hidden triples, plus all easier techniques.
Are triples really needed?
In our Hard puzzles, yes. Without a triple the puzzle does not progress through simpler logic.
Is Hard much harder than Medium?
It is a clear step up because triples are harder to see than pairs. Neat notes make them far easier.