Sudoku
Fill every empty cell so each row, column and box contains the digits 1 to 9 exactly once. Every puzzle has one solution you can reach by logic alone.
How to play Sudoku
How to play
Tap a cell, then tap a number on the pad (or type 1 to 9). Each digit may appear only once in every row, column and outlined box. Tap the same number again, or Erase, to clear a cell.
Notes
Turn on Notes (or press N) to pencil in small candidate digits. When you place a digit, matching notes in the same row, column and box are removed for you.
Levels
Gentle needs only singles: spot the one cell where a digit fits. Moderate adds pairs and pointing pairs. Tough needs X-wings, XY-wings or triples. The Mini 6×6 is a quick warm-up for small screens.
Hints that teach
Hint shows the next logical step, names the technique and explains it in one sentence. Clashing digits are marked with a stripe and a dot, so you can spot them without relying on colour.
Questions
Does every Sudoku here have exactly one solution?
Yes. Every puzzle is checked by a solver that counts solutions, and by a logical solver that proves it can be finished without guessing at its difficulty level.
How are the difficulty levels decided?
By the hardest technique a logical solver needs. Gentle puzzles fall to hidden and naked singles, Moderate puzzles need pairs or pointing pairs, and Tough puzzles need X-wings, XY-wings, swordfish or triples.
How do I add pencil marks?
Turn on Notes with the pencil button or the N key, then tap numbers. You can also hold Shift while typing a digit to add a note without switching modes.
Is there a daily Sudoku?
Yes. The daily puzzle is a Moderate Sudoku that is the same for everyone and changes at midnight UTC.
Can I play Sudoku on my phone?
Yes. The board and number pad are sized for touch, and the Mini 6×6 level is ideal for a quick game on a small screen.