Sudoku generator
Generate classic 9×9 sudoku puzzles with one unique solution. Choose easy, medium, or hard — each level removes a different number of givens (clues). Toggle “show answers” to print the completed grid for teachers or self-check. Every puzzle follows standard rules: digits 1–9 once per row, column, and 3×3 box. Download PDF and print for commutes, classrooms, or senior centers.
Difficulty
How to generate sudoku
1. Pick difficulty: easy, medium, or hard.
2. Click Generate until you like the layout.
3. Optionally enable “show answers” for a solution sheet.
4. Download PDF and print.
Difficulty guide
Easy — newcomers
More givens mean fewer empty cells. Good first puzzles where singles and obvious pairs appear often.
Medium — daily habit
Fewer clues require scanning rows, columns, and boxes together. Typical newspaper level.
Hard — experienced solvers
Many cells blank; solving may need pencil marks for candidates and advanced techniques beyond pure singles.
When to use this tool
• When you want unlimited fresh puzzles without buying books.
• When teachers need matching puzzle and answer PDFs.
• When you prefer paper puzzles over phone apps.
When to choose something else
• When you want 4×4 or 16×16 variants — this tool is standard 9×9 only.
• When you need step-by-step hints or on-screen pencil marks.
• When you require competition-grade graded difficulty beyond three presets.
Structure of a 9×9 grid
Nine rows, nine columns, and nine 3×3 boxes (often outlined thicker in print). A valid sudoku never repeats a digit in any row, column, or box. Solvers cross-check all three constraints when placing a number.
Techniques by difficulty
Easy puzzles fall to “naked singles” — only one digit fits a cell. Medium adds hidden singles and pairs. Hard may require pointing pairs, box-line reduction, or X-Wing patterns. If stuck on hard, pencil small candidate digits in each cell.
Printing for class
Print puzzles Monday, answers Friday — same seed is not fixed, so generate two PDFs: one normal, one with show answers enabled. Students practice logic without screens.
Frequently asked questions
What are the sudoku rules?
Fill the 9×9 grid with digits 1–9 so each row, each column, and each of the nine 3×3 boxes contains all digits exactly once.
How do difficulty levels differ?
Each level removes a different count of clues from a complete valid grid. Hard puzzles start with fewer givens, so logic chains get longer.
Does every puzzle have one solution?
Yes. Puzzles are built from a full valid solution, then cells are cleared while keeping the grid solvable.
Can I print the answer key?
Enable “show answers” before downloading PDF — the file will contain the completed grid.
Are puzzles stored online?
No. Generation is local in your browser.
Can I solve on screen?
There is a preview, but the tool is designed for printing and solving on paper.
Is this free?
Yes, no account needed.