A new 9×9 puzzle arrives every day at midnight UTC, the same for everyone. The week sets the difficulty: Monday and Tuesday are easy, Wednesday and Thursday medium, Friday and Saturday hard, and Sunday is expert.
Fill each row, column and 3×3 box with the digits 1 to 9. Clashing digits turn red as you go; pencil marks (Notes, or the N key) clear themselves when you place a digit they ruled out. Your progress and time are kept in this browser, so you can leave and come back.
Yesterday's puzzle — and every one before it — stays in the archive with its solution.