Sudoku technique: naked singles
A naked single is a Sudoku cell with only one possible digit, because its row, column and box already hold the other eight. Learn to spot one. Solving techniques · lesson 2 of 7.
The lesson in words
Look at one empty cell and list the digits already in its row, its column and its box. If that covers eight different digits, the cell can only be the ninth.
That’s a naked single.
The marked cell sees 1, 2, 3, 5, 6, 7, 8 and 9 in its row, column and box.
Try it: Fill the marked cell.
Count what a cell can see: if eight digits are taken, the ninth goes in. Next: hidden singles.