This online Sudoku solver uses Donald Knuth's Dancing Links algorithm to solve several Sudoku implementations. This algorithm is very fast and can easily be extended to solve a different Sudoku variant. If there is a solution, the solver will find it and makes no distinction between "easy" or "difficult" because all puzzles are converted to an Exact Cover problem first. Current implementations are the regular Sudoku, the Sudoku X also known as the Diagonal Sudoku, the Irregular Sudoku also known as Jigsaw Sudoku or Chaos Sudoku, the Irregular Sudoku X, the Hyper Sudoku also known as Extra Region Sudoku or NRC Sudoku, the Sudoku Tanto and the Offset Sudoku also known as the Even-odd Sudoku. The Toroidal Sudoku or Wrap Around Sudoku can be solved with the Irregular Sudoku Solver.
Usage: Choose one of the Sudoku variants on the left. When you choose a Sudoku with movable cells, drag and drop these cells to match your puzzle first. Next enter only positive decimal numbers to populate the grid and click the Solve button to solve the Sudoku. If there are solutions, the first 10 will be shown. Multiple solutions can be used to solve overlapping Sudoku's. Navigate with the Previous and Next links through the different solutions. The Unsolve button removes the answers so the input can be changed. The Reset button sets the board to its initial state. An error message is displayed when input is against Sudoku rules. The Sudokuspoiler will remember your changes to the board so you can close the browser and continue a next time.