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Verified, browser-local analysis
Sudoku Solver with Step-by-Step Explanations
Enter a Sudoku to check whether it has zero, one, or multiple solutions. For a unique puzzle, Legen replays every supported logical step and explains the technique used.
Enter a 9×9 Sudoku
Type one digit per cell, or paste 81 cells using 1–9 and 0, dot, or dash for blanks. Spaces and line breaks are allowed.
Editing the grid clears the previous analysis.
What this solver verifies
A Sudoku solver checks the constraints of a 9×9 grid and determines how many solutions it has. This tool separates that solution-count result from logical explainability: a unique puzzle is not automatically solvable by the ten techniques Legen currently supports.
- It reports no solution, a unique solution, at least two solutions, or an indeterminate bounded check.
- It never labels a time or search-budget limit as no solution or multiple solutions.
- It shows only logical steps that a separate proof verifier has checked and replayed in order.
- If the supported techniques stall, it does not fall back to exposing a search answer.
Privacy boundary
Your puzzle stays in this browser
Analysis happens in a dedicated worker in your browser. The grid is not sent to a server, added to analytics, stored, or placed in the URL.
Techniques used in explanations
Each displayed move links to its full guide. The current engine covers these ten placement and candidate-elimination techniques.