Last Remaining Cell

The Basics2 / 32

Cross-hatch a box until one cell survives for a digit.

Pick a digit and a box that doesn't contain it yet. Every copy of that digit in a crossing row or column blocks cells inside the box. Often only a single cell survives the crossfire — and that's where the digit lives.

This scanning move, also known as cross-hatching, is the workhorse of sudoku at every difficulty. Most digits you place will come from it.

See it in action

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Step 1 of 4

The setup

Choose a digit that already appears often on the board, then check each box that's still missing it: which cells are blocked by that digit's rows and columns? Step through this real position to see it happen.

Practice

Somewhere a box has exactly one cell left that can take a certain digit. Cross-hatch and place it.

Drill 1 of 29

Tap the cell, then the digit — or type it.