Lesson 6 · Beginner technique
Hidden Singles
Find the only cell in a row, column, or box that can hold a particular number.
See the logic move
Use Next to reveal each reason. On the final step, tap the highlighted cell to complete the move yourself.
Live logical proof · Hidden Single
Step 1 of 3
Focus
5 has only one legal home in row 3: row 3, column 7.
Ask about any cellTap a square on the board
Select an empty cell to see its legal candidates and why the other digits are blocked.
Why this works
- 1
5 has only one legal home in row 3: row 3, column 7.
- 2
Inspect R3C7 and then check its row, column, and 3x3 box.
What the board is showing
TargetThe cell currently being tested.R3C7
Relevant unitThe row, column, or box controlling this move.Row 3
Explain it simply
The answer is hidden among several notes, but that number has only one home in the group.
Step by step
- Choose one row, column, or box.
- Pick a missing number.
- Mark every cell blocked for that number.
- Fill the one legal cell left.
Quick check: Can a Hidden Single cell still contain several candidate notes?
Yes. One candidate is special because it appears nowhere else in that unit.
Turn logic into skill