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

1 2 3 1 2 3 1 2 3
4 5 6 4 5 6 4 5 6
7 8 9 7 8 9 7 8 9
1 2 3 1 2 3 1 2 3
4 5 6 4 5 6 4 5 6
7 8 9 7 8 9 7 8 9
1 2 3 1 2 3 1 2 3
4 5 6 4 5 6 4 5 6
7 8 9 7 8 9 7 8 9
Free Sudoku and Str8ts for Print
Colour Sudoku Solver
Please report any bugs and feedback welcome

Candidates can be Edited or Highlighted / Shown
Enter numbers here:
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 colour. Each colour is in the same position relative to each 3x3 box.

Pick an example from the list and use Take Step to click through the steps of the solver so see how each puzzle solves.
Version 2.12
See Strategy Overview documentation

Coordinate system: Letter/Number rYcX

Check for Solved Cells   
Show Possibles  
1: Singles in Row/Column  
2: Singles in Colour/Box  
3: Naked Pairs/Triples  
4: Hidden Pairs/Triples 
5: Naked Quads 
6: Pointing Pairs  
7: Box/Line Reduction  
Tough Strategies
8: X-Wing  
9: Simple Colouring  
10: Y-Wing  
11: Swordfish  
12: XYZ Wing  
Diabolical Strategies
13: X-Cycles  
14: XY-Chain  
15: 3D Medusa  
16: Jellyfish  
17: WXYZ Wing  
18: Aligned Pair Exclusion  
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 


Please report any bugs - Thanks.

If you are getting errors please
clear your browser cache
to retrieve the latest script files.

The Colour Sudoku Solver

Colour Sudoku is the puzzle as normal Sudoku with an extra constraint. In a similar way to the rows, columns an boxes, the colours must also be uniquely 1 to 9. Each colour is in the same position in each 3x3 box, as you will notice with the central white cell, for example. All Sudoku strategies continue to apply - except the ones that rely on the deadly pattern used by Uniqueness strategies.

The extra constraint does not add any extra complexity in the rows and columns - since a uniqueness constraint already exists, but it does effect cells diagonally. For example, B2, E5 and H8 are now connected and a conjugate pair may exist on those cells. So, like Sudoku X, the solver needs to be aware of all the new diagonal opportunities that are now possible.

Interestingly, this constraint forces the Sudoku puzzle to be 'perfect', that is, every number appears in a different position relative to each 3x3 box.

I have created enough test stock to grade this type of puzzle. However the Solution Count program also needs working on and I hope to make it available in the future.

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.

Colour Sudoku solver created 19th May 2011

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.)

Solver created on 17-Jul-2014.
This page was last modified on 02-Nov-2023.
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