Sudoku

Sudoku needs little introduction: fill a 9×9 grid so every row, column and 3×3 box contains the digits 1 through 9 exactly once. This version generates a fresh puzzle in the browser, checks that the puzzle has a unique solution, and never reuses a grid.

Three difficulties control how many cells are removed, from a relaxed 44-clue board to a 30-clue puzzle that requires real deduction. Conflicts are highlighted as you type, and the hint button fills one cell when you are genuinely stuck.

The timer and hint counter are there for honest comparison, not pressure. Keyboard players can select a cell and type digits directly.

How to play Sudoku

• Click a cell, then enter a digit with the number pad or the keyboard.
• Every row, column and 3×3 box must contain 1–9 exactly once.
• Conflicting digits turn red; erase them with the Erase button or Backspace.
• Solve the grid to stop the timer. Hints fill one cell from the solution.

Tips & strategy

Sudoku is deduction, not guessing. Every puzzle here has a unique solution, so there is always a logical next step.

• Start with the digit that appears most often. Filling its remaining positions usually opens up the grid.
• Scan rows, columns and boxes for a digit that can only fit in one cell — that is a free placement.
• When two cells in a box can only hold the same two digits, those digits cannot appear elsewhere in that box.
• Do not guess. If you are stuck, switch to a different digit or a different region instead of filling a random cell.
• Use the conflict highlighting as a check, not as a crutch; it only catches duplicates, not wrong-but-unique entries.
• Save hints for the last third of the puzzle. Early hints remove the deductions that make the solve satisfying.

Controls

Questions