Sudoku Solver
Type the givens of any Sudoku into the grid - the numbers the puzzle starts with - and this tool works out the rest. It counts solutions instead of just finding one, so it can tell you honestly whether the puzzle in front of you has a single answer at all.
Your grid
Enter the given numbers and leave the rest blank, then solve. If a number repeats inside a row, column or box, the tool marks the repeats instead of solving a broken grid.
How it works
The solver tracks what each empty square can still be, always fills the most constrained square first, and backtracks when a path closes. Because it counts solutions (stopping at two), it can say whether a grid has one answer, several, or none - a solver that stops at the first answer it finds cannot tell those apart.
Stuck on today's puzzle?
Our own daily Sudoku is playable in the browser, with a checker that marks wrong cells without giving anything away: play today's Sudoku. Past days and their solutions live in the Sudoku answers archive.