About the Sudoku Solver

This is a powerful online Sudoku solver that helps you learn and understand various Sudoku solving techniques. Whether you're a beginner or an advanced player, you can use it to:

• Learn solving techniques - Step-by-step display of the solving process with detailed explanations
• Verify your approach - Enter your own puzzles and see the standard solution
• Challenge yourself - Supports puzzles from beginner to extreme difficulty

How to Use

1. Enter a puzzle - Click cells to input numbers, or use "Import/Export" to paste a puzzle
2. Start solving - Click "Next Step" and the solver will analyze and show the next move
3. View explanations - Each step displays detailed technique explanations in the "Hint" area
4. Review steps - Use "Previous Step" to go back and review earlier moves

Shortcuts: Use arrow keys to navigate between cells, Delete to clear, and 1-9 to input directly.

Supported Techniques

The solver tries techniques in order of difficulty, prioritizing simpler ones:

Basic Techniques

• Naked Single - Fill when only one candidate remains in a cell
• Hidden Single - When a digit can only go in one cell within a region
• Naked Pairs - Two cells sharing the same two candidates
• Hidden Pairs - Two digits that can only appear in two cells of a region
• Naked Triples - Three cells sharing three candidates
• Hidden Triples - Three digits that can only appear in three cells
• Pointing/Claiming - Using box-line interactions to eliminate candidates

Intermediate Techniques

• X-Wing - Row-column cross elimination technique
• Swordfish - Extended X-Wing involving three rows and columns
• Skyscraper - Using strong link relationships to eliminate candidates
• Grouped Skyscraper - Grouped version of the Skyscraper technique
• Chute Remote Pairs - Using remote pair relationships between chutes
• XY-Wing - Using three bi-value cells in a chain
• XYZ-Wing - Extended form of XY-Wing

Advanced Techniques

• Unique Rectangle - Using the unique solution property to eliminate candidates
• XY-Chain - Chains connecting multiple bi-value cells
• Strong Links - 3-6 node strong link eliminations
• Forcing Chain - Elimination through hypothesis and deduction
• WXYZ-Wing - Four-cell wing structure

Puzzle Format Guide

The import function supports various common formats:

• Line81 - 81 characters, using 0 or . for empty cells, e.g.: 530070000600195000098000060...
• Grid81 - 9-line format, 9 digits per line
• Grid81 Boxed - 9-line format with separators for easier reading
• Line729 - 729 characters, 9 characters per cell for candidate state
• CSV81 - 81 comma-separated numbers

Related Resources

• Sudoku Strategies Overview - Comprehensive guide to all solving techniques
• Sudoku Glossary - Understanding Sudoku terminology
• Naming Convention - Standard naming for rows, columns, and boxes