Complete Guide: How to Play & Solve Sudoku Puzzles
Sudoku is a popular logic-based number placement game enjoyed by millions worldwide. You don't need math calculations—just logical deduction and systematic scanning!
1. The Fundamental Rules
A standard Sudoku board consists of 81 cells arranged in a 9x9 grid divided into nine 3x3 sub-grids (boxes). The goal is to place numbers from 1 to 9 so that:
- Rows: Every horizontal row contains digits 1 through 9 with no duplicates.
- Columns: Every vertical column contains digits 1 through 9 with no duplicates.
- 3x3 Boxes: Every 3x3 block contains digits 1 through 9 with no duplicates.
2. Core Solving Techniques
Naked Singles
A Naked Single occurs when a specific empty cell has only one possible candidate remaining because all other numbers (1 through 9) are already present in its intersecting row, column, or 3x3 box.
Hidden Singles
A Hidden Single happens when a digit can only legally fit in one specific cell within a row, column, or 3x3 box, even if that cell contains other candidate notes.
3. Intermediate & Advanced Strategies
Pencil Marking (Candidate Elimination)
For tougher challenges like Hard or Expert, use our built-in Pencil Mode to write candidate numbers in empty cells. Eliminating candidates makes hidden patterns visible.
Naked Pairs & Triples
When two cells in the same row, column, or box contain the exact same candidate pair (e.g., [3, 8] and [3, 8]), those digits are locked into those two cells. You can safely remove 3 and 8 from all other cells in that group.
X-Wing Technique
An advanced technique where a candidate number appears in exactly two cells across two parallel rows, and those cells share the same columns. This allows you to eliminate that candidate from those entire columns!
4. Useful Features in Dave's Daily Sudoku
- Number Highlighting: Click any number to highlight every matching digit across the grid instantly.
- Daily Seeded Puzzles: Play a brand new 38-clue challenge every single day at midnight.