Naked Singles Sudoku Strategy

How the strategy works

Look at one empty square and list which numbers are missing from its row, column, and box. If every number is blocked except one, that remaining number is safe.

This is different from guessing because the row, column, and box rule proves the placement.

Large print practice routine

Use this technique slowly on a readable board or a printed sheet. The goal is to remove uncertainty, not to solve faster.

After each candidate cleanup, return to scanning and singles before looking for another advanced pattern.

Naked singles work best when the player slows down enough to prove one square at a time. If several empty cells look possible, choose the one touching the most given numbers because its row, column, and box usually block more candidates.

• Choose one empty square near many givens.
• Check the row for blocked numbers.
• Check the column and box the same way.
• Place the only remaining number.

Example pattern

Example: one empty square is in a row that already has 1, 2, 3, 5, and 9. Its column blocks 4 and 8, while its box blocks 6. The only number left from 1 through 9 is 7, so the square is a naked single.

This is a square-first check. You are not asking where 7 can go everywhere else; you are asking what can fit in this one square after all three Sudoku rules are applied.

Common mistakes to avoid

Do not stop after checking only the row. A number can look available in the row but still be blocked by the column or 3x3 box.

Do not fill several naked singles from memory. Place one, then rescan because the new number changes the rest of the board.