Crosshatching scans rows and columns that intersect a box to determine where specific digits must be placed. The first technique every solver should learn.
Crosshatching is a visual scanning technique used to find where a specific digit must be placed within a box. The process involves looking at the rows and columns that pass through a box and noting which cells are already eliminated for a given digit. If only one cell remains as a possibility, that digit must go there.
The name comes from the mental image of drawing lines across the box - crossing out rows and columns where the digit already exists. These crossing lines "hatch" through the box, leaving only valid cells for placement. For a complete introduction to solving, see our how to play guide.
To crosshatch, pick a digit and a box. Look at the rows passing through that box - if any row already contains the digit, all cells in that row within the box are eliminated. Do the same for columns. Then check which cells in the box already contain other digits. The remaining cells are the only possible locations for your chosen digit.
Crosshatching should be your first approach when looking at any Sudoku puzzle. It is the fastest and most intuitive technique, and it can solve a significant portion of easy and some medium puzzles entirely on its own. Many experienced solvers begin every puzzle by crosshatching through each digit systematically.
The technique is most effective when a digit has been placed in many locations across the grid, as this creates more eliminations and makes it easier to pinpoint the remaining placements. Start with digits that appear most frequently on the grid for the best results.
When crosshatching alone is not enough to make progress, it is time to learn additional techniques. The natural next steps are naked singles (cells with only one candidate) and hidden singles (digits that can only go in one cell within a house).
Together, crosshatching, naked singles, and hidden singles form the core toolkit that can solve the majority of published Sudoku puzzles. Explore more terms in the Sudoku glossary.
Crosshatching is a basic Sudoku solving technique where you scan the rows and columns that pass through a box to determine where a specific digit must go within that box. By eliminating cells that are already ruled out, you can often find the only possible position for a digit.
Yes, crosshatching and scanning are essentially the same technique. Some resources call it crosshatching because you mentally draw crossing lines through the box along occupied rows and columns. Others call it scanning because you scan for where a digit can fit. Both terms describe the same process.
Crosshatching alone can solve many easy Sudoku puzzles, but it is not sufficient for medium or harder puzzles. As difficulty increases, you will need additional techniques like naked singles, hidden singles, and more advanced strategies to make progress.
Practice scanning systematically by working through each digit 1 through 9 across the entire grid. Start with digits that appear most frequently, as they have fewer remaining placements. With practice, you will develop pattern recognition that makes crosshatching nearly instantaneous.
Where can the digit 5 go in row 1? Two cells already hold 4 and 8 — but the rest are empty.
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