Then try some of our extra-fiendish puzzles.
The basic rules of Sudoku are easy. Just place the digits from 1 to 9 in each empty cell. Each row, column, and 3 x 3 box must contain only one of each of the 9 digits.
Solving these puzzles is a different matter entirely, since these are the most difficult puzzles we create. Difficulty depends on the type of steps required to solve them, and also on the number of each type of step.
All the puzzles on this site rate a "fiendish" category, but then we picked the hardest, and graded them in five progressively more difficult categories: Evil, Excessive, Egregious, Excruciating, and Extreme, in order from least difficult to most difficult.
To print the puzzles use either the Print button below the grid, or if you want to print the pencilmarks as well, use the browser Print option under the File menu.
The Show Conflicts button does not apply the solving logic - just checks whether there are any conflicting digits already in the grid. So it's possible to have incorrect digits that don't conflict, but eventually you will get stuck.
There are automatic pencilmarks that appear if you check the Pencilmarks box. These update by themselves as you solve particular cells and cannot be edited manually.
If you prefer to enter your own pencilmarks, up to six numbers can be entered in each cell.
To save any position, right-click on Permalink under the grid, and click Add To Favorites or Bookmark This Link. The position is saved as 81 digits at the end of the URL string, with hyphens used for empty cells.
Extreme Sudoku posts five new puzzles every day. Each puzzle has a unique solution and can be solved with pure logic. Lots of it. Guessing is never required - but it may help!