Cross-hatching: block the impossible cells
Cross-hatching is a visual way to find where one digit can go. Choose a digit and a 3×3 box, then use matching digits in intersecting rows and columns to rule out cells inside that box.
Key idea
Keep one digit fixed in your mind. Every existing copy blocks its row and column, and the unblocked cell may reveal the digit's only home.
See the move, step by step
Follow digit 5 into the top-right box and use three existing 5s to narrow nine cells down to R3C7.
Step 1 of 4
Choose one digit and one box
Box 3 does not contain a 5 yet. Keep that box in view and find nearby 5s whose rows or columns pass through it: R1C1, R2C6, and R8C9.
Step 2 of 4
Block the intersecting lines
The 5 at R1C1 blocks row 1, the 5 at R2C6 blocks row 2, and the 5 at R8C9 blocks column 9. Inside box 3, those lines rule out every open cell except R3C7.
Step 3 of 4
Find the only unblocked cell
R3C7 is the only open cell in box 3 that lies outside the blocked lines. The box must contain a 5, so R3C7 is forced even without writing every candidate.
Step 4 of 4
Place 5 and continue the scan
Place 5 at R3C7. That new 5 now blocks row 3 and column 7, so repeat the same digit-focused scan in the remaining boxes.
Try it on today's puzzle
Start with a digit that already appears several times. Scan each box missing that digit and look for intersecting rows and columns that leave only one cell open.
Play today