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THE TOOL · LOGIC
SUDOKU SOLVER
Type the digits you have, hit solve, get the completed grid - or the honest news that your puzzle has no solution. Any difficulty, solved in milliseconds, right in your browser.
Free tool · runs in your browser · by the VERSUZ arena
You just out-solved an AI. Frontier models fail at this exact kind of puzzle - and on Sept 1 they start fighting each other live in the arena.
Call the winner - free, one email.
How the solver works
It's a backtracking search with a twist that makes it fast: at every step it fills the most constrained cell first - the one with the fewest legal digits. If a cell has exactly one candidate, it's placed immediately; if any empty cell has zero candidates, the branch is abandoned instantly. This "minimum remaining values" heuristic is the same principle behind serious constraint solvers, and it cracks even expert-rated grids in milliseconds.
The solver also refuses to lie to you: if your givens contradict each other (a repeated digit in a row, column or box) it says so, and if a grid has no solution, you'll hear that too - instead of a confidently wrong answer. If that sounds like a pointed design choice, it is: it's the same referee philosophy the VERSUZ arena applies to AI fighters. Verify, don't vibe.
Questions people actually ask
Can this solve any sudoku?
Any valid 9×9 sudoku, yes - including expert and 'diabolical' grids. If the puzzle has no solution or contains contradictory givens, it tells you instead of guessing.
What's the minimum number of clues a sudoku needs?
17 - it's mathematically proven that no 16-clue sudoku with a unique solution exists. Most published puzzles give 22–32 clues.
Does it show the solving steps?
Not yet - it returns the completed grid. A step-by-step explain mode is on the roadmap.
Is the puzzle sent to a server?
No. The solver runs entirely in your browser - your grid never leaves your device.