Claiming candidates
A digit's candidates in a row or column all lie in one box. Remove that candidate from the rest of the box.
In column 2, 4 can go only in box 7. The box's other cells therefore cannot contain 4. Remove candidate 4 from the box outside column 2.
What to look for
Check a whole row or column for a digit whose candidate positions all lie in the same box. This technique is also known as box/line reduction.
Why it works
The row or column must contain the digit in that box. The box cannot contain the digit again in any of its other cells.
Try it step by step
- Find every candidate position for a digit in a row or column.
- Check that all those positions lie in one box.
- Remove that candidate from the box's cells outside the line.
Try it on a real puzzle
Start with the highlighted step, then keep solving. Use "Apply hint" to make the suggested change, or enter your own digits and candidate notes. Use "Undo" to reverse your last change.
| C1 | C2 | C3 | C4 | C5 | C6 | C7 | C8 | C9 | |
|---|---|---|---|---|---|---|---|---|---|
| R1 | |||||||||
| R2 | |||||||||
| R3 | |||||||||
| R4 | |||||||||
| R5 | |||||||||
| R6 | |||||||||
| R7 | |||||||||
| R8 | |||||||||
| R9 |
Use the arrow keys to move, 1-9 to enter a digit and Backspace or Delete to clear a cell. To add or remove a candidate, press C and then 1-9.
Source puzzle number: 110430 · Play this puzzle from the start
A simple example
If the only candidates for 7 in row 1 are R1C1 and R1C2, remove candidate 7 from rows 2 and 3 of the top-left box.
A house is a row, column or 3 × 3 box. A line is a row or column. Two cells "see" each other when they share a house. R1C3 means row 1, column 3. Boxes are numbered 1-9 from left to right and top to bottom. Braces such as {1, 2} show a cell's candidates, not confirmed digits.