Cross-hatching is a basic [Sudoku technique](https://sudokubliss.com/guides/sudoku-tips-and-strategies) that helps you find where a number can be placed by using imaginary lines to cross out the rows and columns where the number already is. It relies on a fundamental Sudoku rule: Numbers can only appear once in each column, row, and block. So those lines eliminate cells where the number could go and help you see its possible placements.

Cross-hatching is especially useful early in Sudoku puzzles because it can reveal answers without requiring you to use [candidate mode](https://sudokubliss.com/guides/sudoku-candidate-mode) or pencil marks first, and repeated cross-hatching may also create new solving opportunities elsewhere in the puzzle.

Beginners and advanced solvers all use this strategy. And the more you use it, the faster you’ll become at placing candidates and eliminating possibilities when you’re [playing Sudoku online](https://sudokubliss.com/).

## How to Use Cross-Hatching in Sudoku

Unlike patterns you have to find, like [X-wings](https://sudokubliss.com/guides/x-wing-technique) or [skyscrapers](https://sudokubliss.com/guides/sudoku-skyscraper), cross-hatching is a simpler Sudoku strategy. Just follow these steps:

1. **Identify a candidate that already exists in the Sudoku grid.** Don’t get too preoccupied with determining which candidate to target. This works quickly, so you won’t need to be too methodical. For example, candidate 5 is in cells A6, B9, F2, and H1.
2. **Choose a block that doesn't already contain the candidate, and draw lines through the rows and columns where the candidate can't be placed.** For example, a line should be extended from the 5 in the following cells to cross out cells as possibilities in the top-left block.  
  * H1 through row 1
  * F2 through row 2
  * A6 through column A
  * B9 through column B
3. **Determine if the number can be placed as an answer or a candidate.** If only one cell in a block has no lines in it, you can place the number in that cell as the answer. If more than one cell in a block has no lines in it, you must place the number as a possible candidate in each cell. For example, only one empty cell is left in the top-left block with no line crossing it out. So candidate 5 can be placed into C3.
![How to use cross-hatching in Sudoku example](https://sudokubliss.com/content-uploads/how-to-use-cross-hatching-in-sudoku.webp)  

**Remember:** Don’t worry if you don’t place candidates immediately. Finding where they could possibly be placed is extremely important because you can revisit those as you solve more cells in the grid.

Cross-hatching is different from [Sudoku scanning](https://sudokubliss.com/guides/sudoku-scanning).

* **With scanning,** you’re **looking for what’s missing** in rows, columns, and 3x3 blocks to see where a candidate could possibly be placed.
* **With cross-hatching,** you’re **looking for where a candidate is blocked from going** to highlight where a candidate could possibly be placed.

## Sudoku Cross-Hatching Examples

Cross-hatching doesn’t always offer you a placement, but it does eliminate where candidates can go and show where pencil marks can be made. Placing possible candidates allows you to see patterns that are used for more [advanced techniques](https://sudokubliss.com/guides/sudoku-advanced-strategies).

### Cross-Hatching Example: Candidate Placement

When you have just one possible cell in which a candidate can be placed, you’ve found a [naked single](https://sudokubliss.com/guides/naked-singles-technique). In the following example, you’ll see how cross-hatching results in placing a candidate in the grid.

1. **Identify a candidate that already exists in the Sudoku grid.** For example, 1 is already placed in cells A5, C2, E3, and G8.
2. **Choose a block that doesn't already contain the candidate, and draw lines through the rows and columns where the candidate can't be placed.** For example, a line should be extended from the following cells to cross out cells as possibilities in the bottom-left block.  
  * A5 through column A
  * C2 through column C
  * G8 through row 8
3. **Determine if the number can be placed as an answer or a candidate.** For example, candidate 1 can be placed into B7, the only cell with no lines in it.
![Cross-hatching Sudoku example with a candidate placement](https://sudokubliss.com/content-uploads/cross-hatching-example-with-candidate-placement.webp)  

Candidate 1 can also be cross-hatched just from rows 2 and 3\. Doing so reveals that only one cell in the top-right block is open, so 1 can be placed in I1.

### Cross-Hatching Example: Candidate Possibilities

Sometimes cross-hatching doesn’t result in placing an answer in a cell. In the following example, you’ll see how cross-hatching results in placing candidates as possibilities in the grid.

1. **Identify a candidate that already exists in the Sudoku grid.** For example, 2 is already placed in cells B1, D3, E4, and H7.
2. **Choose a block that doesn't already contain the candidate, and draw lines through the rows and columns where the candidate can't be placed.** For example, a line should be extended from the following cells to intersect in the bottom-left block and cross out the possibilities.  
  * B1 through column B
  * H7 through row 7
3. **Determine if the number can be placed as an answer or a candidate.** For example, two cells don’t have lines going through them, which means you can’t place 2 as an answer in a single cell. But you can make it a candidate in cells A8 and A9\. While you haven’t solved a cell, the candidate possibilities you’ve narrowed down may reveal patterns like [hidden pairs](https://sudokubliss.com/guides/hidden-pairs-technique) or [swordfish](https://sudokubliss.com/guides/swordfish-technique) that help you solve other cells.

Candidate 2 can also be cross-hatched in the bottom-middle block from columns D and E and row 7\. Doing so reveals that you can place 2 as an answer in F9.

![Cross-hatching Sudoku example with candidate possibilities](https://sudokubliss.com/content-uploads/cross-hatching-example-with-candidate-possibilities.webp)  

While you can find plenty of cross-hatching opportunities in [easy puzzles](https://sudokubliss.com/), it’s powerful enough to narrow down possibilities and place answers in cells in [expert-level puzzles](https://sudokubliss.com/expert). The next time you [play Sudoku](https://sudokubliss.com/), practice cross-hatching and see how quickly it can help you solve your next grid.