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Sudoku Solver for Android
Check out the App features.
Strategies for Popular Number Puzzles
Please report any bugs and feedback welcome
Weekly 'Unsolvable'
Puzzles to Play
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
Free Sudoku and Str8ts for Print
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

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.
Read up on Windoku strategy.

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
Boxes Rows Columns
1 2 3 4 5 6 7 8 9
Version 2.20
See Strategy Overview documentation

Coordinate system: Letter/Number rYcX

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

Errors? [CRTL]+[F5] to clear and download the latest script files

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)
Added Windoku

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 Gonçalves, 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.
This page was last modified on 12-Jun-2024.
All code and design is copyright and for personal use only and may not be reproduced elsewhere.
Copyright Andrew Stuart @ Syndicated Puzzles, 2005-2023, Privacy