Random Sudoku Generator
Generate a fresh Sudoku puzzle — every puzzle is checked to have exactly one valid solution, not just filled with random holes.
Generate
How the Random Sudoku Generator works
A grid full of random holes doesn't guarantee a solvable, single-answer Sudoku puzzle — many random removals would leave a puzzle with multiple valid solutions, which isn't a real Sudoku puzzle at all. This generator checks uniqueness properly: after removing each cell, it runs an actual constraint-solving search that stops as soon as it finds a second valid solution, and only keeps that cell removed if the puzzle still has exactly one.
The starting grid itself is generated with genuine randomness (using a randomized backtracking fill), so no two generated puzzles use the same underlying solution — this isn't a small library of pre-made puzzles.
How to use it
Frequently asked questions
Is every generated puzzle guaranteed to have exactly one solution?
Yes — each cell removal is verified against an actual solution-counting search before being kept, so every finished puzzle has been confirmed to have exactly one valid solution, not just 'probably' one.
Why does Hard difficulty sometimes take a moment to generate?
As more clues are removed, it becomes harder to find further cells that can be removed while preserving a unique solution, which means more computation — this is inherent to generating genuinely difficult, uniquely-solvable puzzles, not a bug.
Can I check my answer as I go?
The 'Show solution' button reveals the complete answer at once; there's currently no cell-by-cell hint or check-as-you-go feature.