Internet Sudoku

Technique

Naked single Sudoku technique

A naked single is an empty square where only one digit can legally fit. Once you prove that, the move is certain.

What it means

For one empty square, list the digits that are not already used in its row, column, and 3 by 3 box. If that list has one digit, the square is a naked single.

The single is called naked because the answer is visible from the candidates for that square, not hidden among other squares in a unit.

When it appears

Naked singles often appear after you place a nearby number and remove that digit from related notes. They are common in easier puzzles and also show up as cleanup moves in harder puzzles.

Simple text example

Suppose a square already sees 1, 2, 3, 4, 5, 6, 7, and 9 in its row, column, or box. The only digit left is 8, so that square must be 8.

Practice next

Play Daily SudokuLook for naked singles in today's puzzle.Hidden singleLearn the next simple single technique.All techniquesReturn to the technique index.Sudoku tipsBuild better scanning and note habits.

Sudoku Tips

Sudoku gets easier when you solve with a repeatable scan instead of searching the whole grid at once.

Tip 1: Look for rows, columns, or 3 by 3 boxes that already contain several numbers. The more filled-in an area is, the fewer places a missing digit can go.
Tip 2: Work one number at a time. Scan every box for where that number can still fit, then compare those open spots with the crossing rows and columns.
Tip 3: Use notes when a square has only a few real candidates. After every confirmed number, clean up notes in the same row, column, and box.