Sudoku puzzle generator
Generate a valid sudoku puzzle with a guaranteed unique solution, at three difficulty levels. Play right online or reveal the solution at any time. No puzzle is sent to a server: everything is calculated in your browser.
How it works
The grid is first completely filled in a random but valid way (each row, column and 3x3 block contains the digits 1 to 9 with no repeats), then cells are removed one by one as long as the puzzle keeps a unique solution — a true sudoku never has several possible solutions.
How are the difficulty levels determined?
The difficulty level corresponds to the number of empty cells: about 35 for "easy", 45 for "medium" and 54 for "hard". The more empty cells there are, the more logical deduction is needed to complete the grid.
How do I check my grid without cheating?
Fill in the cells, then click "Check": the tool compares your entries with the internal solution without showing it. Use "Show solution" only if you're stuck.
The grid is generated and checked entirely locally, with no network request at all.