Sudoku Solver
Type the numbers from any Sudoku puzzle into the grid and this solver fills in the complete answer instantly, right in your browser. Nothing is uploaded, and it works even when you are offline.
Enter your puzzle, then press Solve.
What is a Sudoku solver?
A Sudoku solver is a tool that takes an unfinished Sudoku puzzle and works out the completed grid for you. You enter the numbers the puzzle starts with, and the solver fills in every empty square so that each row, each column, and each 3x3 box contains the digits 1 to 9 exactly once.
A good solver does more than reveal the answer. It checks whether the puzzle you entered is valid and tells you whether it has a single solution, more than one, or none at all. This one does all of that in your browser in well under a second, so you can finish a puzzle from a newspaper or book, confirm an answer you worked out yourself, or test a puzzle you are creating.
How to use the solver
- Click a square and type the number that belongs there. Repeat for every given clue.
- Press Solve to fill in the rest of the grid. Your clues stay dark and the answers appear in a lighter colour.
- Stuck on your own puzzle? Press Hint to reveal a single correct square, or Check to flag squares that break the rules.
- Use Load example to try a sample puzzle, Clear to start over, or Copy link to save or share the puzzle you entered.
How the solver works
The solver combines candidate elimination with backtracking search. For every empty square it works out which digits are still possible, always fills the most constrained square first, and backtracks whenever a choice leads to a dead end. That is enough to solve any valid 9x9 Sudoku in a fraction of a second.
All of this runs on your device. The puzzle you type never leaves your browser, so the solver is private and keeps working with no connection once the page has loaded.
When a puzzle cannot be solved
The solver tells you why a grid does not have a clean answer:
- Conflicting clues: the same digit appears twice in a row, column, or 3x3 box. The clashing squares are highlighted so you can fix them.
- No solution: the clues are consistent but cannot be completed into a full grid. Re-check the numbers you copied.
- Multiple solutions: too few clues are given, so more than one grid fits. The solver shows one valid answer.
More Sudoku help
Frequently asked questions
Is this Sudoku solver free?
Yes. The solver is completely free, needs no account, and you can solve as many puzzles as you like.
Does the solver work offline?
It runs entirely in your browser. Once the page has loaded, it solves puzzles without an internet connection and never uploads what you type.
How do I enter a puzzle?
Click a square and type its digit, then use the arrow keys to move around. You can also paste an 81-character line of digits (use 0 or a period for blanks) to fill the whole grid at once.
Why does it say my puzzle has multiple solutions?
A well-made Sudoku has exactly one solution. If too many squares are left blank, several different grids can satisfy the clues, so the solver fills in one valid answer and lets you know.
Why does it say the puzzle has no solution?
Either two of the given numbers repeat in the same row, column, or box, or the clues cannot be completed. Check the highlighted squares for a duplicate and correct it.
What is the fewest clues a Sudoku can have?
A standard 9x9 Sudoku needs at least 17 given numbers to have a single unique solution.