Version 12.2


New Features

1. New version of the Buried analyses (Buried Pairs, Buried Triples and Buried Quads). The new version executes much more quickly and catches a number of scenarios that were missed by the previous version. Note that Buried Quads is only available with the Advanced Analyses license feature.

Bug Fixes

1. When the 'Hide Grading' option was selected, an attempt to grade would result in the message 'NO DIFFICULTY FACTOR - NEEDS SPLITS ANALYSIS'. Now, a dialog box pops up : 'First de-Select 'Hide Grading' in the Options menu'.

2. When grading a Knight's Move SuDoku, the full solution would not appear until the mouse had been moved off-grid, causing a refresh. Now, a refresh occurs at the end of the grade.

3. Printing of the cover page of a number of Virtual Puzzle Books was not correctly implemented.

4. Options Help panel updated with information about setting window and panel heights.

Version 12.1


New Features

1. Further to the Autoscale mode option added in the last release, additional options allow the manual resizing of the Main Window height and the Mode Panel height. In addition, the Main Window height can be adjusted temporarily with the mouse by dragging the top or bottom of the Window. Again, this is to overcome issues seen by some users where the grid did not display correctly. More details are here.

2. Similarly, the Selector Window height (Virtual Puzzle Book View or List View) can be adjusted with options, or temporarily changed with the mouse.

3. There is a new analysis, 'Buried Quadruples', which is similar to 'Buried Pairs' and 'Buried Triple', but for sets of 4. This analysis is only available when the 'Advanced Analyses' feature is licensed.

4. There is a new analysis, 'Impossible Solutions', which is a much more rigorous version of the 'Splits' analysis (aka 'Guess'). This analysis is only available when the 'Advanced Analyses' feature is licensed. 'Splits' proceeds by guessing which of a pair of possible solutions is correct and just keeps going until a complete solution is reached. There is no guarantee that the resulting solution is unique. 'Impossible Solutions' only proceeds if it can find a contradiction after each 'trial', thereby ensuring that any solution is unique. It also allows full tracing of each trial, showing how the contradiction is reached.

5. There is a new expanding Virtual Puzzle Book available. 'MegaBook 2021 Plus' contains every puzzle that has appeared on the 'Puzzles' page of this website since January 2021. It never stops growing! One click to update the book with the latest puzzles. Contains Classic SuDokus, Killer SuDokus, Variant SuDokus (eg. Knights Move), and Hidden Picture SuDokus.

6. When closing the application, there is now a dialog box to ask for confirmation that this is what you would like to do.

Bug Fixes

1. Some incorrectly entered puzzles caused the 'Check' button to lock up with the message "Guess Count = zero !!".

Now the 'Check' will exit properly with the message: "The SuDoku as-is has no solution. It is (remotely) possible that the SuDoku is 'real' and the Solver just can't find the solution. It is much more likely that the SuDoku is incomplete, or a mistake has been made when entering it."

2. When loading Picture SuDokus from the the Virtual Puzzle Books 'MegaBook 2014' and 'MegaBook 2015', the pictures did not display.

3. Snyder notation is not used for Killer SuDokus, but it was still possible to change little numbers (notes) to bold font if 'Snyder with a Mouse' option was enabled. Snyder notation now completely disabled for Killer SuDokus.

4. In Virtual Puzzle Book view, clicking on the last two (blank) pages of the book could cause it to lock up.

5. In Virtual Puzzle Book view, redrawing the display could sometimes be faulty when scrolling through the book.

6. The QuadPairs analysis, which assumes uniqueness, was being used as part of the check that a SuDoku was unique! This is no longer the case. Instead the 'Check' button will report if a SuDoku can be solved with QuadPairs, but not without - meaning it is probably not unique.

Version 12.0


New Features

1. Knights Move Knight's Move SuDoku has arrived! This is the first of a number of SuDoku Variants that will be added to the Solver in due course. SuDoku Variants is a licensed feature. The license key will work with all new Variants as they become available. Next in the pipeline are Queen/Bishop's Move, King's Move and Diagonal SuDoku. If there are other SuDoku Variants that you would like to be added, send an email to and they may be added if there is sufficient demand.

2. Knights Move FREE Knight's Move SuDokus will now appear in the free Cracking The Cryptic Virtual Puzzle Book; and will also appear on the Puzzles page of this website.

3. Knights Move A new Virtual Puzzle Book is now available called Knight's Move SuDoku, containing 100 brand new puzzles exclusive to this website. Difficaulty Factors range from 'Easy' to 'Ultimate'. More details are here.

4. An Autoscale mode option has been added to the options menu. This allows Autoscale to be set to 'Font' (the default until now), 'DPI', or 'None'. This is to overcome issues seen by some users where the grid did not display correctly. More details are here.

Bug Fixes

1. Double click is now treated as two single clicks, rather than just one. So, when using the 'Snyder with mouse' option, it is possible to more rapidly cycle between blank, normal font, bold font.

2. In List View, the 'End' button would jump beyond the last SuDoku if the number of SuDokus was an exact multiple of 20.

3. The 'Save' button (and 'Save' in the File menu) only appear in Capture and Solve modes. They no longer appear when in any of the Advanced Analyses modes, or when in Clue mode. This is to prevent confusion about exactly what is being saved.

4. Some very difficult Killer SuDokus puzzles caused the solver to get stuck in an infinite loop when Grading or using the Splits analysis.

5. In Print or Print Preview, Uniques (little red squares) were not displaying correctly.

Version 11.0


New Features

1. Support for Snyder Notation has been added. Snyder notation is where a possible can only occur in two positions within a 3 X 3 box. For a good explanation of Snyder notation,
see this video from the 'Cracking The Cryptic' YouTube channel.

Now Snyder possibles can be shown in bold font to distinguish them from other possibles.

When hovering the mouse over a little number, use the 'S' button to mark it as a Snyder possible (bold font), or left click the mouse to mark it as a normal possible (normal font). In addition, under options, there is a new setting 'Snyder with mouse'. If this is checked, then left clicking the mouse will cycle a little number between blank, normal font and bold font.

If you need some help spotting all the Snyders, a new button 'Snyd' has been added near the 'Poss' and 'Clue' buttons. This will populate the whole grid with all Snyder possibles based on the current position.

2. For Killer SuDokus, the 'Impossibles in Groups' analysis has been improved to cover groups of eight squares.

3. For Killer SuDokus, the 'Associates' analysis has been improved to operate on Groups as well as Rows, Columns and Boxes. Details can be seen here.

Bug Fixes

1. In 'Virtual Puzzle Book' the left hand YouTube button would appear on top of the help panel, if the help panel was viewed.

2. The grid labels were not displaying correctly when solving Killer SuDokus.

3. Print Preview threw up a strange error message if no default printer was set, or if the default printer was offline, or if the default printer had no drivers.

4. Small pink squares (eg. when showing Associates analysis) were difficult to see on some displays. 'Pink' changed to 'Hotpink' (a darker pink).

Version 10.2


New Features

1. The 'Cracking The Cryptic' Virtual Puzzle Book now contains links to the YouTube videos of the puzzles from the 'Cracking The Cryptic' YouTube channel. Buttons on the main Solver panel, as well as in the 'Virtual Puzzle Book' and 'List View', take you straight to YouTube! Full details here.

2. To aid navigation in large Virtual Puzzle Books, buttons for jumping to the end and jumping to the beginning have been added to both 'Virtual Puzzle Book' and 'List View'.

Bug Fixes

1. When downloading the latest SuDokus from the website, the count of new SuDokus was incorrect.

2. When entering a Killer SuDoku it was possible to corrupt the count of group totals by expanding one group over the top of another one.

Version 10.1


New Features

1. Significant enhancement to the Rows and Columns analysis (aka 'X-Wing) to include 'finned' variants (aka 'Finned X-Wing' and 'Sushimi Finned X-Wing'). Full details may be seen here.

2. Check for latest version at start-up. This check (which is also still available from the Help menu) is now performed at start-up. The start-up check can be inhibited in the Options menu.

3. Virtual Puzzle Books that 'grow' can now download Killer SuDokus as well as standard SuDokus. For example, the 'Cracking The Cryptic' Virtual Puzzle Book now includes Killer SuDokus - more details here.

Bug Fixes

1. Quad Pairs analysis (aka 'Unique Rectangles') would only spot scenarios with just one extra Possible in the 4th Square of the pattern. In fact, the logic works for any number of extra Possibles in the 4th Square. This has been fixed and Quad Pairs should recognise a lot more scenarios. Full details may be seen here.

2. Minor improvement to the GUI: when using any key ( delete a Solution or populate a Square with Possibles), the re-drawing of the dark blue outline square was not always working correctly.

Version 10.0


New Features

1. Additional shortcut keys have been added ('P' was already a shortcut key for populating a single Square with all possible solutions) so the full list of shortcut keys is:

P - Populate a single Square with all possible solutions.
C - Clear a single Square of all possible solutions (ie clear all Little numbers, or "pencil marks", from that Square).
B - Toggles between Big Numbers and Little Numbers
Right Mouse - Toggles between Big Numbers and Little Numbers

2. 'Open' added to File menu. This opens List View. Does exactly the same as selecting 'List View' from the Tools menu, but added following several requests. Also added separate buttons on the Toolbar for 'Virtual Puzzle Book' and 'List View'.

3. Support for a new Puzzle Book Cracking The Cryptic. This Puzzle Book is FREE and features SuDokus from the YouTube channel of the same name, see here. Many of the videos on this channel feature Duncan's SuDoku Solver - so a great place to see it in action!
This Puzzle Book grows! New puzzles will be regularly added and can be downloaded for free - full details here.

Bug Fixes

1. In Killer mode, the Save button (and Save option in the File menu) did not appear unless a name was first typed into the name box.

2. With Microsoft Windows 10, the File Browser (the magnifying glass button in Virtual Puzzle Book and List View) stopped operating correctly and did not allow browsing of folders or creation of new folders. A new setting ('before Windows 10) has been added in the Options menu. It should be unchecked for running in Windows 10 and checked for all earlier versions of Windows. Some very early versions of Windows 10 may also require this option to be checked to get correct operation of the File Browser.

3. In Solve Mode, gross Mistakes (Square is coloured red) were showing up even if the 'Mistakes' checkbox was not checked.

4. In List View, if the first line of the comments was too long, it could overflow into the 'Required Analyses'. Now truncated to fit into the comments area.

Version 9.0


New Features

1. In Solve Mode, when clicking on the Clue Button, the Help Detail box and the '?' cursor turn on automatically and the Clue Button turns red to indicate 'Clue Mode'. They will turn off automatically when clicking on the grid to return to Solve Mode (or when entering Solve Mode from any other Mode). The '?' button still allows the Help Detail box to be turned on and off manually.

2. Support added for a new type of Virtual Puzzle Book - MegaBooks. These are a collection of ALL the SuDokus published on the website during the year. The collection is updated with all the SuDokus published to-date at the click of a button.
More information is here.

3. For Killer SuDokus, several new enhancements have been made to the 'Impossible Combinations' analysis to tackle some particularly tough puzzles. Full details are here.

Bug Fixes

1. Using the "Poss" button to populate the whole grid with possible solutions, or using the 'P' key to populate a single Square with possible solutions, did not start the timer if elapsed time was zero.

2. A Solution in a Square did not always remove Possibles of the same value elsewhere within the same Group.

3. Going into List View (or Virtual Puzzle Book) and then exiting without loading a SuDoku, caused STEP mode to advance one step.

4. In List View, deleting a folder that contained files other than SuDoku files caused a crash.

Version 8.4


New Features

1. Picture SuDokus are now displayed in a different way. Previously, either the picture or the SuDoku grid were displayed depending on if the mouse was hovering over the grid. This caused the picture to flicker on and off in a distracting way. Now, the picture can be displayed (or not) under user control. Also the picture can be faded in and out to show both picture and grid overlayed.

Bug Fixes

1. In List View, SuDoku names could be truncated to 25 characters when the mouse cursor hovered over them.

2. In Capture Mode for Killer SuDokus, there were some pixels not being correctly re-drawn when the blue Group outline moved away.

3. In Capture Mode for Killer SuDokus, the blue Group outline was not drawing in the left column and the top row when the cursor was brought in from off-grid.

4. When loading a SuDoku, a 'PAUSED' message would show even if elapsed time was zero. Now, if a SuDoku is reset to the start position, and the SuDoku is saved without starting it, the 'PAUSED' message will not show when that SuDoku is re-loaded.

5. Returning from List View or Virtual Puzzle Book without selecting a SuDoku could cause the cursor not to display the blue highlight square in Capture and Solve modes.

6. When downloading a Killer SuDoku from the website, the message "The new SuDoku has been downloaded" would display even if a Killer SuDoku had not been downloaded, due to the Killer Solver feature not being licensed and the demo period of 30 days having expired.

7. Saving a Picture SuDoku that had been downloaded from the website, sometimes caused it to become unlicensed.