Naked Single

The Basics3 / 32

A cell whose candidates have shrunk to one.

Look at a single cell and collect everything that blocks it: the digits in its row, its column and its box. If those neighbors use eight different digits between them, only one candidate survives.

Naked singles hide in plain sight — the cell looks unremarkable until you actually count what's still possible in it.

See it in action

123456789

2

7

1

8

123456789

4

3

5

1

5

123456789

123456789

123456789

3

123456789

123456789

7

3

123456789

123456789

123456789

7

5

123456789

1

2

7

4

5

3

9

123456789

123456789

123456789

1

2

123456789

123456789

7

1

4

3

5

123456789

123456789

3

1

123456789

5

8

123456789

7

4

4

1

2

123456789

123456789

7

5

123456789

3

8

7

123456789

5

123456789

123456789

1

4

123456789

5

123456789

123456789

123456789

123456789

1

7

2

123456789

Step 1 of 4

The setup

Cells with many filled neighbors are prime suspects. Check crowded rows and columns where they cross a crowded box. Step through this real position to see it happen.

Practice

One cell on this board has exactly one candidate left. Find it and fill it in.

Drill 1 of 29

Tap the cell, then the digit — or type it.