How to play sudoku
The grid has 9 rows, 9 columns and 9 boxes of 3×3 cells. Some cells already contain a digit. Your job is to fill every empty cell so that:
- each row contains the digits 1 to 9 exactly once,
- each column contains the digits 1 to 9 exactly once,
- each 3×3 box contains the digits 1 to 9 exactly once.
Every puzzle on PuzzleSheets has exactly one solution, and you never need to guess. Each one is checked by a computer solver before you see it.
Using the player
- Tap or click a cell, then tap a number. On a keyboard, type 1–9 and use the arrow keys to move.
- Turn on Notes (or press N) to pencil in candidates. Placing a digit removes it from the notes in the same row, column and box.
- Check highlights wrong entries. Highlight conflicts shows duplicates as you play.
- Your game is saved on this device automatically. Use Save code / Continue later to get a code or link that restores the exact puzzle, your progress and your time on any device.
What the difficulty levels mean
Difficulty is rated by the hardest technique you need, not just by how many digits are given.
| Level | Techniques you will need |
|---|---|
| Easy | Singles only: the last cell in a row, column or box, and hidden or naked singles. Plenty of clues. |
| Medium | Pointing and claiming (locked candidates), naked and hidden pairs. |
| Hard | Triples and quads, X-wing and XY-wing. |
| Expert | Swordfish, jellyfish, XYZ-wing or simple colouring. |
Tips for getting better
- Scan for hidden singles first. Pick a digit and look at each box: is there only one cell where it can go?
- Use notes on harder puzzles. Medium and harder puzzles are much easier once you write candidates down.
- Look for pairs. If two cells in a row can only hold 4 and 7, no other cell in that row can be 4 or 7.
- Box–line interactions. If a digit in a box can only be in one row, it can’t appear in that row outside the box.
- Stuck? Take a break. Use Save code and come back later with fresh eyes.
Printing
Open Print or download under the grid to get a free PDF on A4 or US Letter, with 1, 2, 4 or 6 puzzles per page and an optional answer key. Printed sheets never contain ads. Each printed puzzle also shows a short code, so you can continue it online later.