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Sudoku for complete beginners

How to start a Sudoku: make your first move with logic

Choose a row, column, or 3×3 box that is nearly full. Find the missing digits first. Then check each empty cell’s crossing row or column before you place anything.

One visible proof

This repeated check is called scanning: find what is missing, then rule out the places where it cannot go.

  1. 1. Find what is missingRow 1 is missing 2 and 7.
  2. 2. Check the crossing columnColumn 3 already contains 2, so the first empty cell cannot contain 2.
  3. 3. Place only what is provedThe first empty cell must contain 7. The other empty cell then contains 2.
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Row 1 needs 2 and 7. Column 3 already contains 2.

✓ The row needs 2 and 7. The crossing column rules out 2, so the outlined cell must contain 7.

Try it yourself

Use this reasoning on a fresh grid.

The interactive lesson shows one example, then lets you make the next check.

Practice scanning free →No account needed. Your progress stays on this device.