Sudoku Solver for AndroidCheck out the App features. SudokuWiki.org Strategies for Popular Number Puzzles
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Window numbers Referred to in strategy results are:

 9 5 5 5 9 6 6 6 9 7 1 1 1 7 2 2 2 7 7 1 1 1 7 2 2 2 7 7 1 1 1 7 2 2 2 7 9 5 5 5 9 6 6 6 9 8 3 3 3 8 4 4 4 8 8 3 3 3 8 4 4 4 8 8 3 3 3 8 4 4 4 8 9 5 5 5 9 6 6 6 9
 Windoku Solver Solve Path now excludes unchecked strategies ↓
Candidates can be Edited or Highlighted Chained Coloured,  Shown
Enter clues or solutions
 1 2 3 4 5 6 7 8 9
 Auto Tab Auto Clear
Clues+Solved: 0/81
 Pick an example here Pick an example here Easiest Windoku Gentle Moderate Tough Diabolical Moderate 14 Clue Densest Clues Naked Triples Pointing Pairs LBR examples Y-Wing examples XYZ Wing Swordfish X-Cycles XY Chains 3D Medusa Jellyfish Crazy Extreme

Puzzle Rules
Enter the numbers 1 to 9 uniquely in every row, column, box and each 'window'. It turns out that while four windows are shown on the paper version there are actually nine.

Pick an example from the list and use [Take Step] to click through the steps of the solver so see how each puzzle solves.

 Show bi-values cells Show Strong (bi-location) links in Windows Boxes Rows Columns 1 2 3 4 5 6 7 8 9
 A B C D E F G H J
 Version 2.20 See Strategy Overview documentation Coordinate system: Letter/Number rYcX
 1 2 3 4 5 6 7 8 9
 Check for Solved Cells Show Possibles 1: Singles 2: Pairs 3: Triples 4: Quads 5: Pointing Pairs 6: Box/Line Reduction Tough Strategies 7: X-Wing 8: Simple Colouring 9: Y-Wing 10: Rectangle Elimination 11: Swordfish 12: XYZ Wing Diabolical Strategies 13: X-Cycles 14: XY-Chain 15: 3D Medusa 16: Jellyfish 17: WXYZ Wing Extreme Strategies 19: Grouped X-Cycles 20: Finned X-Wing 21: Finned Swordfish 22: Altern. Inference Chains 23: Sue-de-Coq 24: Digit Forcing Chains 25: Nishio Forcing Chains 26: Cell Forcing Chains 27: Unit Forcing Chains 28: Almost Locked Sets 29: Death Blossom 30: Pattern Overlay Method 31: Quad Forcing Chains "Trial and Error" 32: Bowman's Bingo

Note: All Chaining strategies now permit cycling alternatives, where found read more

## The Windoku Solver

Quite a few people have asked me to add this so I'm very pleased to get this finished at last. May be knock on bugs with the other solvers, do let me know.

Windoku is the same puzzle as normal Sudoku but with an extra constraint. In a similar way to the rows, columns an boxes, the Windows must also be uniquely 1 to 9. The paper version shows just four windows, but as is explained here there are actually nine. All Sudoku strategies continue to apply - except the ones that rely on the deadly pattern used by Uniqueness strategies.

All feedback, comments, arguments, bug reports and strategy ideas are welcome. There is a new FEEDBACK form with a column displaying comments and questions. Many thanks to all the people who have done so and helped improve this solver.

New in version 2.15, 2.16 (May 2024)
New and much faster Solution Count.
New Solution Count and Email popups.
Packed strings for transporting candidates allowed on url and import

New in version 2.14 (May 4th 2024)
Improved sanity check. Added candidate chaining and colouring.

New in version 2.10 (October 8th 2023)
Added chain cycling. If more than one chain is found the solver will provide buttons to cycle through them. Longstanding feature now implemented. More information on What's New

Version 2.05 (March 26th 2016)
Expanded Windoku to take advantage of all nine 'windows'
See Windoku Strategy documentation

Version 2.03 (November 11th 2015)

Full version history here

## Solver help

Use the "Import a Sudoku" button or type in a Sudoku puzzle in the small board.
You can also pick examples from the list above. Click on Take Step to step through the solution. Unknown squares are filled with 'candidates' - possible solutions.
Any cells that are reduced to one possible candidate are solved.

You can use the [<<] button to step back one go. Toggling between Take Step and [<<] helps you see the changes.

Pressing "Enter" on the keyboard after clicking on Take Step is a quick way to activate "Take Step". Details of any solutions will be written out in the text box below the big board. Strategies are ordered by complexity. Any strategy that is successful returns the step-through to the start.

Click on the board to highlight sets of numbers. You can edit the Sudoku at any time - entering solutions in the small board or editing candidates. (Toggle between highlighting and editing using the radio buttons at the top.)

 All Solutions to a Windoku By Andrew Stuart and Rui GonÃ§alves, Syndicated Puzzles
 Email your puzzle to a friend Copy and paste the contents of the green box into your email program and send it off. The links contain the puzzle which will load when your friend visits the Sudoku Solver.
Solver created on 11-Nov-2015.