Does each puzzle have only one solution?

Yes. After removing clues the generator checks the remaining grid with a solver and only keeps a removal if the puzzle still has exactly one unique solution.

What do the difficulty levels mean?

Difficulty controls the number of given clues — easy keeps around 40, medium around 32, and hard around 26. Fewer clues generally means a harder solve.

Is my puzzle generated on a server?

No. The full backtracking solver and puzzle generation run in your browser, so nothing is sent anywhere.

Sudoku Generator

Generate unique-solution sudoku puzzles — easy, medium, hard.

Printable sudoku with a guaranteed unique solution

Generate fresh 9x9 sudoku puzzles in easy, medium, or hard difficulty. Each puzzle is built with a backtracking solver and then checked to confirm it has exactly one unique solution, so there is never any ambiguity.

Generate, print or save as a PDF, then reveal the answers with one click when you are ready. Everything happens in your browser.