Solver App for Android
Strategies for Popular Number Puzzles
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Feedback and Questions

I've received a lot of interesting comments and questions from Sudoku fans over the last few years and this page is where I try to answer them. I'm also directing Str8ts feedback here. Please feel free to drop me a note on the side of the page. Or you can email me directly at .

Post a Comment or Question here...
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Any Sudoku you want to publish here for easy loading into the solver - 81 characters, use '.' or '0' for unknowns.

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Many thanks to all the people who have helped improve the solvers and strategies with their feedback!

Sunday 24-Nov-2019

... by: Shelli, Washington, DC (USA)

Thank you SO MUCH for the new secure site! You can't image how worried I was about the FBI monitoring my Sudoku activity. ;-)

Andrew Stuart writes:
I know, just don't get radicalized. :0

Sunday 24-Nov-2019

... by: Michael, Germany

Dear Andrew,

my Sudoku Android App doesn't download the daily puzzles anymore. Is this because you moved your site to HTTPS?

Regards Michael

Andrew Stuart writes:
That's possible, maybe doesn't like the 301 redirect. It should not care but that's apps. However, last night I found a way to put the /feed part onto http alone. Any problem today?

Thursday 21-Nov-2019

... by: DUANE RAEBURN, usa

Can I use your solver to do cell logic ( only these numbers can go here) and box logic ( this number can here or here)? I hope that is clear. This is a nice site and thank you for all the work you have done on this.

Andrew Stuart writes:
Do you mean, no constraints on rows and columns? Just cells and boxes?
Sounds like a Magic Square
Currently, no, not in the solver as set up

Saturday 16-Nov-2019

... by: Håkan Holgersson, Sverige

Hello Andrew Stuart! Wonderful site! Thanks!

Andrew Stuart writes:
Thanks Håkan!

Wednesday 13-Nov-2019

... by: Pat, United States

Have you taken your website down? It seems broken. I hope not, I have enjoyed using it for years! It sure helps when you get stuck on a puzzle.

Andrew Stuart writes:
Server is tempremental and I am in the process of porting to a new one.

Monday 11-Nov-2019

... by: Phil Turner, England

Load Sudoku:

This sudoku appeared on "Cracking the Cryptic" and is not solvable by your programme. However, it can be solved using just hidden/naked digits and wings, if wings is extended beyond jellyfish. Do you consider wings greater than 4 by 4 to be unusable in practice? Best wishes, Phil.

Andrew Stuart writes:
This puzzle found a bug in the Gurth detection. It caused 5 to map to 0 which screwed everything up. Now fixed. If you manually add 5 into the center cell E5 it will be a gurth puzzle and some detections are made. Either way it solves relatively, mainly with X-wings

I believe the 5x5 extension of a Jelly-Fish is called as Squirm-Bag. But it is redundant since if it exists then a corresponding 4x4 Jelly-Fish will exist and that should be used instead.

Friday 4-Oct-2019

... by: Nigri, India

i am new to difficult sudoku. Learning new techniques. i didnt know about a 3�3�3 swordfish only 2x2x2. Your trick helped me solve a puzzle. I have been stuck for weeks. Thanks

Andrew Stuart writes:

Thursday 3-Oct-2019

... by: Annie, NZ

Such a brilliant tool! Best on the net, has helped me learn so many techniques, thank you so much! Any chance you're developing a Kakuro Solver?

Andrew Stuart writes:
Thanks so much, very kind.
I can make Kakuro puzzles so I can solve them, so internally I do have a solver. But I've found that there are not many special strategies so its of much less interest than, say, Sudoku. It would just munch through them rather than explaining anything very clever.

Sunday 29-Sep-2019

... by: Gary Jones, USA

I am a longterm sudoku user I generally try to solve the diabolical versions but this week I am stopping in running the solver and have purged my browers cache.... I use Microsoft edge..... but still am stopped in my tracks . I then have to solve the puzzle by hand and my own devices.

this sunday puzzle had a solver error to start with but I still try to solve the puzzle but the next step is greyed out and I have tried the remedies to no avail.

I have not tried easier puzzles so far to see if the same thing occurs but there does seem to be a problem with my browser.

I really used this game religiously and would appreciate your help.

Andrew Stuart writes:
My bad, I didn't reset the version number to all the solvers. The normal Sudoku should have been ok, no?
Just patched the rest of them now

Thanks for the alert

Tuesday 4-Jun-2019

... by: ChrisP235, UK

Just wanted to say this is brilliant. So much more effective for learning sudoku strategies than trying to work through videos/text! Thanks for the hard work.

Andrew Stuart writes:
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Thank-you everyone for all your questions and contributions.