Sudoku Generator
Generate Sudoku puzzles with a guaranteed single solution in four difficulty levels, then solve, copy or download them.
Fill the blanks with 1–9. Use the arrow keys to move between cells.
How it works
Every puzzle starts as a complete, valid 9×9 grid built by randomised backtracking: the solver walks the board cell by cell, tries the digits 1–9 in a shuffled order and backs up whenever a row, column or 3×3 box would repeat a digit. Clues are then removed in 180°-rotationally symmetric pairs, and after each removal a counting solver re-checks the board and stops as soon as it finds a second solution. A pair is only kept out if exactly one solution remains, so the puzzle you get always has a single, logically reachable answer — never a guess between two valid grids.
Difficulty sets how many clues the generator aims to leave behind: 40 for Easy, 32 for Medium, 28 for Hard and 24 for Expert. Symmetry occasionally makes the exact target impossible without creating a second solution, so the actual clue count is shown above the grid. Type a seed and the same seed plus the same difficulty always rebuilds the identical puzzle — handy for sharing a grid with a friend or printing the same sheet twice. Leave the seed empty for a fresh random puzzle every time.
You can solve the grid right here — type digits into the blank cells, move around with the arrow keys, and press Check answers to see which entries are wrong. Copy puzzle puts the grid on your clipboard as nine lines of text (dots for blanks) and Download .txt saves the puzzle, the seed and the full solution. Everything runs locally in your browser: no uploads, no accounts, no ads.
Frequently asked questions
Does every generated puzzle have only one solution?
Yes. The generator starts from a complete, valid grid and removes clues in 180°-rotationally symmetric pairs. After every removal a counting solver re-solves the board and stops as soon as it finds a second solution — the pair is only left out when exactly one solution remains. So the puzzle can always be finished by logic alone, never by guessing between two valid grids.
What do the difficulty levels mean?
Difficulty sets how many clues the generator aims to leave: 40 for Easy, 32 for Medium, 28 for Hard and 24 for Expert. Fewer clues means more deduction before the grid opens up. Because symmetric removal sometimes cannot hit the exact target without creating a second solution, the actual clue count is always shown above the grid.
Can I get the same Sudoku puzzle again?
Yes — type anything into the Seed field. The same seed with the same difficulty always rebuilds the identical puzzle, so you can print the same sheet twice or share a grid by sending the link with ?seed=42&difficulty=hard on the end. Leave the seed empty for a brand new random puzzle each time.