Sudoku Generator

Create uniquely solvable 9×9 Sudoku puzzles, play in the browser or print them with separate solutions.

Generating

Choose a target number of givens and press New puzzle. Generation runs in a browser worker and can be cancelled. A value is removed only when the remaining puzzle is proven to have exactly one solution. Some targets cannot be reached in the bounded search; the actual number is then reported. Fewer givens do not guarantee a harder puzzle. These are density targets, not human difficulty grades.

Playing

• Enter digits 1-9; givens cannot be changed. Arrow keys move around the board, Home/End within a row, Ctrl+Home/End across the board. Enter moves down and never starts a new puzzle.
• Check marks wrong values against the unique solution and reports empty cells. Editing clears the old message; after checking, wrong entries remain marked as you edit.
• Hint fills the selected editable cell, or the next empty/incorrect cell if the selection is fixed or already correct. It reveals a solution digit, not a human solving technique.
• Show solution fills the board; Reset entries restores the original puzzle.

Printing and privacy

Puzzle + solution prints the original puzzle and its solution on separate A4 pages with 15 mm margins. Entries are not printed. Create 4-puzzle sheet prepares four new independent puzzles; then use Print 4-puzzle sheet. Their numbered solutions are on a second page. Printing uses the browser dialog, including Save as PDF. Settings, board entries and prepared sheet remain only in memory during navigation; reload clears them. Generation and checks stay in the browser, without uploads.