One solution
Nine diagonal cells are removed from a completed grid. Each row is missing exactly one number, so there is only one way to finish it.
Sudoku checker
Enter or paste a puzzle to check for conflicts, no solution, multiple solutions or a unique answer.
Checked in your browser. No account needed.
Your puzzle
63 clues · 18 empty cellsKeyboard: arrow keys move; 1–9 enter a clue and move to the next empty cell; 0, Delete or Backspace erase. Home/End move within a row. Ctrl/⌘ + Z undoes; Shift + Ctrl/⌘ + Z redoes. Tab leaves the grid.
Enter clues
Enter or paste the clues, then check the puzzle.
Enter 81 cells row by row: 1–9 for clues, 0 or . for blanks. Spaces, line breaks and grid separators are ignored.
Import replaces the grid; Undo restores it.
Example puzzles
Load an example, then check it. This replaces your input; Undo restores it.
Conflicting clues
The two 1s in row 1 repeat in the same row and box. Both conflicting cells are marked.
No solution
Row 1 needs a 9 in column 9, but that column already contains a 9. There are no repeated clues, yet no valid completion exists.
Multiple solutions
All 1s and 2s are removed from a completed grid. Swapping 1 and 2 gives different valid completions, so the remaining clues cannot select one answer.
How to check a Sudoku
- 01 / Enter
Enter the puzzle
Enter the original clues or include your own entries to check your progress. All entered numbers are treated as fixed.
- 02 / Check
Read the diagnosis
The checker finds duplicates, then searches for solutions. It stops at two solutions or 15 seconds; an interrupted check gives no conclusion.
- 03 / Continue
Continue solving
Correct your clues, view the answer or learn about Sudoku candidates. The checker shows answers without a logical walkthrough.
Conflicting clues
A number repeats in a row, column or box. Correct the marked cells.
Read the guideNo solution
No digits repeat, but the clues cannot form a solution. Check the original puzzle.
Read the guideMultiple solutions
At least two solutions fit. Check for missing clues; no arbitrary answer is shown.
Read the guideOne solution
This puzzle has one solution. You can view the full answer.
Read the guideSudoku solver questions
Can a Sudoku have no duplicates and still be impossible?
Yes. Clues can make a puzzle impossible without repeating a digit. In the no-solution example, row 1 needs a 9 where the column already has one.
Why won’t the checker show one answer when several exist?
Several solutions mean the clues do not determine one answer. Check for missing numbers; a standard Sudoku should have a unique solution.
Does this support diagonal, killer or other Sudoku variants?
Only standard 9 × 9 Sudoku is supported: each row, column and 3 × 3 box contains 1–9 once. Variant rules are not checked.
Is my puzzle sent to a solving service?
Checks run in your browser. Typed or pasted clues are not sent to a solving service. A puzzle in the URL is included in the page request.