Lesson 5 · Beginner technique
Naked Singles
Solve a cell when its candidate list has been reduced to one number.
See the logic move
Use Next to reveal each reason. On the final step, tap the highlighted cell to complete the move yourself.
Step 1 of 3
Focus
row 5, column 5 has only one legal candidate: 5.
Select an empty cell to see its legal candidates and why the other digits are blocked.
- 1
row 5, column 5 has only one legal candidate: 5.
- 2
Inspect R5C5 and then check its row, column, and 3x3 box.
What the board is showing
Explain it simply
A Naked Single is not hiding: its cell openly shows just one possible candidate.
Step by step
- Choose an empty cell.
- Check its row, column, and box.
- Cross out blocked candidates.
- Place the only candidate left.
From demonstration to independent solving
Prove the move yourself
What you should be able to do
Distinguish a cell with one legal candidate from a cell that merely looks likely to contain a digit.
Read the exact board evidence
At R5C5, eight digits are already represented among its row, column and box peers. The candidate calculation returns only 5. Because there is no alternative inside that cell, placing 5 is a direct consequence of the rules.
When the logic is strong enough
Write the complete candidate list before calling a Naked Single. If two digits survive, the cell is not solved even when one seems more convenient.
Train the pattern without guessing
After every placement in an Easy puzzle, inspect the affected row, column and box for cells whose candidate lists have just fallen from two options to one.
Quick check: If a cell has candidates 3 and 8, is it a Naked Single?
No. A Naked Single has exactly one candidate.
Turn logic into skill