Sudoku Generator

The Sudoku Generator creates a fresh, random 9×9 Sudoku puzzle at the difficulty you choose — Easy, Medium, Hard, or Expert — that you can either solve right there in your browser or print to play on paper. Each click of New Puzzle builds a brand-new grid from scratch, so you get effectively unlimited puzzles without an account, a download, or any data leaving your device.

It's aimed at the everyday reasons people want a sudoku on demand: a quick brain-training break, a printable sheet for a classroom or care home, or a stack of puzzles to take on a flight where there's no Wi-Fi.

The generator runs entirely in your browser and builds each puzzle in two stages. First it generates a complete, valid solution: starting from an empty 9×9 grid, it fills every cell using randomized backtracking — for each empty square it tries the digits 1–9 in a shuffled order, keeps a digit only if it doesn't already appear in that row, column, or 3×3 box, and recurses, backing up when it hits a dead end. Because the digit order is shuffled every time, you get a different filled grid on every run. Then it copies that solved grid and blanks out cells in a random order until the number of remaining clues (the digits you start with, or "givens") matches your chosen difficulty.

Difficulty is controlled purely by how many clues are left on the board — fewer clues means a harder puzzle:

• Easy — about 38–45 clues. Plenty to work from; good for beginners and kids.
• Medium — about 30–37 clues. The default, balanced for casual solvers.
• Hard — about 25–29 clues. Requires more scanning and pencil-marking.
• Expert — about 17–24 clues. Sparse and demanding. (Seventeen is the known mathematical minimum number of clues a proper Sudoku can have.)

The exact clue count within each band is itself randomized, so two "Hard" puzzles won't have the same number of givens. As you play, the full solution is kept in the background so the Hint, Check, and Solve buttons can compare your entries against the right answers.

Honest note on unique solutions: this generator removes clues randomly and does not re-test the puzzle to guarantee exactly one solution. For Easy and Medium grids the large number of clues means a single solution is overwhelmingly likely in practice. For very sparse Expert grids it's possible to land on a puzzle with more than one valid completion. If you need a guaranteed-unique puzzle (for a graded test or a published book), generate at a higher clue count, or verify the puzzle in a solver first.

1. Pick a difficulty — tap Easy, Medium, Hard, or Expert. (It starts on Medium.)
2. Click "New Puzzle" to generate a fresh grid at that difficulty.
3. Solve it on screen (optional): click a blank cell to select it, then tap a number on the on-screen pad — or use your keyboard. Type 1–9 to enter a digit, Backspace/Delete to clear a cell, and the arrow keys to move between cells. The starting clues are locked.
4. Use the helpers if you get stuck. Hint fills one random empty cell with its correct value; Check highlights any numbers you've entered that are wrong; Solve reveals the complete answer (it asks for confirmation, since it ends the game).
5. Watch the timer and progress. A live clock tracks your time and an "X/81 filled" counter shows how close you are. Finish a valid grid and you get a "Solved in MM:SS" message.
6. Print or share. Print opens a clean, printer-friendly version of the puzzle; Share posts a link to the tool via WhatsApp.

Worked example — generating a Hard puzzle. Pick Hard and click New Puzzle. The tool builds a full solution behind the scenes, then blanks cells down to, say, 27 clues (a value it picks at random within the Hard band of 25–29). You see a 9×9 grid with 27 bold starting digits and 54 empty cells; the progress reads 27/81 filled and the timer starts at 00:00. You click the empty top-left cell, use the arrow keys to move around, and press 5 to drop a 5 in. If you mistype, Check turns the wrong cells red; stuck on the last few, Hint fills one correct digit. Complete the grid correctly and you get "Congratulations! Solved in 09:42!". Prefer paper? Click Print for a single-page grid showing only those 27 clues — no answer key — ready to photocopy.

• Daily brain training — a quick logic workout with difficulty you can dial up as you improve.
• Printable classroom & worksheet packs — teachers generating Easy/Medium grids as printable warm-ups or filler.
• Care homes, waiting rooms & libraries — printable puzzles for people who'd rather work on paper than on a screen.
• Travel & offline play — print a few before a flight or road trip with no connection.
• Puzzle practice at a target level — drilling a specific difficulty (e.g. Expert) to train particular solving techniques.
• Casual on-screen play — a no-install, no-signup sudoku you can play in the browser with hints, error-checking, and a timer.

• Difficulty is about clue count, not a "technique" rating. This tool grades by how many givens remain (Easy = most, Expert = fewest). It doesn't classify by the human solving techniques required the way some puzzle books do — a good proxy, but a different labelling system.
• Expert puzzles may not be uniquely solvable. Clues are removed randomly with no uniqueness check, so a sparse Expert grid can occasionally have more than one valid answer — which means Check (it compares against the one solution the tool generated) could flag a different-but-valid entry as wrong. If a strictly unique puzzle matters, use a higher clue count or verify it in a solver.
• The printout is the puzzle only. Print gives you the blank grid with its clues, not the solution. If you want the answers too, use Solve on screen before closing the tab — there's no printed answer key.
• "New Puzzle" replaces the current one. Generating again (or changing difficulty and generating) wipes your in-progress grid and resets the timer. Finish or print before you regenerate.
• It's a single grid, not a batch. There's no "generate 10 puzzles" or multi-page export. To make a printable pack, generate and print one puzzle at a time.
• Output is on-page plus print, not a downloadable image. There's no PNG/SVG/PDF download button. To save a puzzle as a file, use your browser's "Save as PDF" inside the Print dialog.
• Allow pop-ups for printing. Print opens the printable sheet in a new window; if your browser blocks pop-ups, the print view won't appear.
• Everything runs locally. Puzzles are generated in your browser, so nothing is uploaded — but a puzzle isn't saved anywhere either, and refreshing the page loses the current grid.

Are the puzzles really random? Yes. The full solution is built with a shuffled backtracking fill, so the underlying grid differs every time, and the clues that remain are removed at random positions. You won't get the same puzzle twice in any practical sense.

Does each puzzle have only one solution? Usually, but not guaranteed. The tool doesn't run a uniqueness test after removing clues. Clue-rich Easy and Medium grids are effectively always unique; very sparse Expert grids can occasionally have more than one valid solution. For anything you're publishing or grading, verify in a solver first.

Can I print the puzzle, and does it include the answers? You can print, and the printout contains just the puzzle (its starting clues) — no answer key. To see the solution, use the Solve button on screen before you leave the page.

What makes Expert harder than Easy? Fewer starting clues. Easy keeps roughly 38–45 of the 81 cells filled; Expert keeps only about 17–24, so you have far less to deduce from and need more advanced scanning.

Do I need an account, and is my data uploaded? No account, and no upload. The whole tool runs in your browser, so your puzzles and progress stay on your device.