🧠 Complete 9x9 Sudoku Rules & Strategy Masterclass

SudokuPlay.org combines an interactive, tournament-standard 9x9 puzzle generator with in-depth educational guides. Unlike luck-based games, every authentic Sudoku puzzle is solved purely through logical deduction.

1. The Golden Rule of 9x9 Sudoku

A standard Sudoku grid consists of 81 cells divided into nine 3x3 blocks (also called houses or boxes). To solve the puzzle, every row, every column, and every 3x3 block must contain the digits 1 through 9 exactly once—with zero duplicate numbers in any unit.

2. Core Solving Techniques for Every Difficulty

• Cross-Hatching & Hidden Singles: Scan rows and columns intersecting a 3x3 box to eliminate occupied lines until only one empty square can hold a target digit.
• Naked Pairs & Triples: Use Pencil Notes (press N) to track candidate digits. When two cells in the same house share the exact same two candidates, remove those digits from all other cells in that house.
• Pointing Pairs (Box-Line Reduction): When a candidate digit inside a 3x3 box is restricted to a single row or column, eliminate that candidate from the rest of that row or column outside the box.
• X-Wing & XY-Wing: In Expert and Extreme puzzles, look for two rows where a candidate appears in the exact same two columns—forming a rectangle that clears all other occurrences in those columns.