Sudoku strategies
Solving Sudoku means reducing possibilities through logic, not guessing. Read the row, column, and 3 x 3 box around each cell so every placement can be checked.
Recommended solving order
Start with the most complete units, scan one number through every box, and rescan after each certain placement. Add candidates only when a cell cannot yet be solved.
Naked singles
A naked single has one legal candidate. A hidden single is a number that fits in only one cell of a row, column, or box.
Naked pairs and locked candidates
Two cells with exactly the same two candidates form a naked pair. Locked candidates connect a box with a row or column and remove that candidate outside the box.
Advanced techniques
When basics stop working, review hidden pairs, triples, X-Wing, and other row-column patterns. Apply a pattern only when every position is accounted for.
Common mistakes
- Guessing because a number looks likely.
- Keeping stale notes.
- Forgetting one of the three units.
Frequently asked questions
Advanced techniques are not required for every board. Use notes when no placement is certain and compare legal possibilities without guessing.
A reliable routine is to scan, note, eliminate, place, and rescan. Keep the explanation for each move clear enough that you could undo it safely.
A useful routine is to scan, note, eliminate, place, and rescan. Keep each deduction clear enough to undo safely, and review the three connected units whenever the board changes.
If you get stuck, do not fill the grid with guesses. Return to the last confirmed move, refresh the candidates, and search for a deduction that affects several cells at once.