Sudoku Board
How to Play Sudoku
Sudoku is a logic puzzle played on a 9×9 grid. No math and no guessing required — just careful elimination. Here's everything you need to know to solve a grid from start to finish:
- Fill in every row. Each of the 9 rows must contain the digits 1 through 9 with no repeats.
- Fill in every column. Each of the 9 columns must also contain the digits 1 through 9 exactly once.
- Fill in every 3×3 box. The grid is divided into nine smaller 3×3 boxes, and each one must contain the digits 1 through 9 with no repeats.
- Use the clues. Some cells are already filled in when a puzzle starts — these given numbers are fixed and are your starting logic.
- Select a cell and enter a number. Tap an empty cell, then tap a digit on the number pad, or press 1–9 on your keyboard.
- Use pencil marks for candidates. Turn on Notes mode to jot down possible numbers in a cell before committing to a final answer.
- Watch for mistakes. Cells highlighted in red don't match the puzzle's solution — fix them to keep going.
- Finish the grid. The puzzle is solved the moment every row, column, and box is correctly filled.
Frequently Asked Questions
What are the rules of Sudoku?
Sudoku is played on a 9x9 grid split into nine 3x3 boxes. Fill every row, column, and 3x3 box with the digits 1 through 9 so that no digit repeats within any row, column, or box. Each puzzle starts with some cells already filled in as clues, and every properly made puzzle has only one correct solution.
How do pencil marks (notes) work in this Sudoku game?
Turn on Notes mode with the pencil button, then select a cell and tap the candidate numbers you want to track. Small numbers appear inside the cell instead of a final answer, helping you keep track of possibilities. Placing a real number in a cell automatically clears its notes, and a correct entry also clears that number from the notes of related cells in the same row, column, and box.
What's the difference between easy, medium, and hard Sudoku?
Difficulty is controlled by how many starting clues are given and how much deduction is required. Easy puzzles leave more numbers filled in and can be solved with simple scanning. Medium puzzles remove more clues and need basic elimination strategies. Hard puzzles leave the fewest clues and require deeper, multi-step logic. Every puzzle, at any difficulty, always has exactly one valid solution.
Is this online Sudoku game free to play?
Yes. Every puzzle is generated for free directly in your browser, with no downloads, accounts, or payment required. You can generate a new puzzle at any difficulty as many times as you like.
Does this Sudoku game work on mobile devices?
Yes. The board and number pad resize to fit phones and tablets, and every cell can be filled in by tapping the on-screen number pad, so no physical keyboard is required.