How to play

Goal: fill every empty square with a number from 1 to 9.
The rule: each row, each column and each of the nine 3×3 boxes must contain every number from 1 to 9 exactly once.
Entering numbers: tap a square, then tap a number on the pad or type it on your keyboard. Arrow keys move around the grid.
Notes: switch to Notes (or press N) to pencil in small candidate numbers. Notes clear themselves when you place a number that rules them out.
Mistakes: by default the game doesn't tell you when a number is wrong, just like a puzzle on paper. Turn on "Show mistakes" in the options if you'd like a heads-up.

Tips

Start with the numbers that already appear most often on the grid.
Look for a square where only one number is possible, and for a number that has only one possible square in a row, column or box.
On hard and expert puzzles, notes are your friend. Pencil in candidates and look for patterns.

Sudoku is the number puzzle that needs no math at all, just logic. Every puzzle here has exactly one solution and can be solved without guessing. Pick a difficulty from easy to expert, or play the Daily Sudoku that everyone gets on the same day.

Hints that teach

Stuck? A hint first points out any number that's wrong. Otherwise it finds the next square that can be solved by logic and tells you why, for example "this is the only square in the row where a 7 can go."