The 7 Sudoku Solving Strategies, From Beginner to Expert

1. Scanning (the bread-and-butter)

Pick a digit. Look at each 3×3 box and ask: where can this digit go? Often only one cell is possible. Place it, move to the next box. After all nine boxes for one digit, move to the next digit. Most easy and medium puzzles are mostly solvable through scanning alone.

2. Pencil marks (notes)

When scanning runs out, write candidate digits in each empty cell. Then look for cells with only one candidate, or rows/columns/boxes where a candidate appears in only one cell.

3. Naked pairs

If two cells in a row both have exactly two candidates {3, 7}, those digits must occupy those cells. So remove 3 and 7 from all other cells in that row.

4. Hidden pairs

The flip side: if two digits can only go in two specific cells of a row (even if those cells have other candidates marked), you can reduce both cells to just those two digits.

5. Pointing pairs (box-line reduction)

If within a 3×3 box, all candidate cells for a digit lie in the same row, then that digit must go in that box. Remove the candidate from the rest of the row outside that box.

6. X-Wing

When a candidate digit appears in exactly two cells in each of two different rows, AND those four cells line up in two columns, you have an X-Wing. Remove that candidate from all other cells in those two columns.

7. Chaining / forcing chains

For expert-level puzzles. Pick a cell with two candidates. Assume one is true, follow the consequences. If a contradiction arises, you know the other candidate is correct. Powerful but mentally taxing.

Practice the first four on Medium difficulty. The last three are only needed for Hard and Expert.