Hard Sudoku
About 30 starting digits. Expect to use pairs.
- Time
- 0:00
- Mistakes
- 0
About Hard Sudoku
Hard puzzles start with around 30 filled cells. Expect long stretches where no single cell is obvious and you have to narrow candidates down first. Hard puzzles often need pairs: when two cells in a unit share the same two candidates, those digits can be removed from every other cell in that unit.
How to play
Fill the grid so every row, every column and every 3x3 box contains each digit from 1 to 9 exactly once. Some cells are filled in to start, and there is only one correct solution.
Tap a cell, then tap a number. Turn on Notes to pencil in possible digits, and use Undo if you change your mind. A digit that breaks the solution is shown in red. On a keyboard, use the arrow keys to move, the number keys to fill, N for notes, H for a hint and Z to undo.
Tips for this level
- Fill in full candidate notes early. Most hard techniques are about removing candidates, not placing digits.
- Look for naked pairs and triples: two cells sharing the same two candidates lock those digits out of the rest of the unit.
- Look for pointing pairs: if a digit in a box is confined to one line, remove it from the rest of that line.
New puzzles are generated in your browser and checked to have a single solution, so you can play as many as you like. Your progress is saved on this device. New to the game? Read how to play Sudoku.