Reference
Solving techniques
Every Ranked Sudoku difficulty tier is defined by the hardest technique its puzzles require. Learn each one below, with an animated grid walking through the steps.
- Naked SingleOnly one digit can possibly go in this cell.Easy
- Hidden SingleA digit that only fits in one cell of a row, column, or box — even if that cell still has other candidates.Medium
- Pointing PairWhen a digit's only spots in a box line up on one row or column, it can be eliminated elsewhere on that line.Medium
- Naked PairTwo cells in a unit that share the exact same two candidates lock those digits down.Hard
- Hidden PairTwo digits confined to the same two cells of a unit, even if those cells list other candidates too.Hard
- Naked TripleThree cells in a unit whose candidates combine to exactly three digits.Hard
- Hidden TripleThree digits confined to the same three cells of a unit, hidden among other candidates.Hard
- X-WingA digit trapped in the same two columns across two rows forms a rectangle you can eliminate around.Expert
- Y-WingThree bivalue cells linked by two shared digits eliminate a third digit from their common neighbors.Expert
- SwordfishThe same idea as X-Wing, extended to three rows and three columns.Expert
How Sudoku works
A Sudoku grid is 9×9 cells, split into nine 3×3 boxes. Fill every cell with a digit from 1 to 9 so that no digit repeats within any row, column, or box. The puzzles here start with some cells already filled in — the techniques above are how you work out the rest.
Read solving guides on the blog →