Hard Sudoku: A Friday Brain Workout to Play Online

Friday brings our hardest Sudoku of the week. Fill every row, column and 3-by-3 box with the digits 1 through 9, and remember that there is no rush.

How to Play

• Tap a square, then tap a number to place it.
• Every row, every column and every 3-by-3 box must contain 1 through 9 once.
• Use Check to test your grid, Hint for a nudge, or Show answer if you would like to see the solution.
• Your progress is saved on this device, so you can finish later.

A Tip for Harder Sudoku

Scan for a number that already appears many times on the grid, such as a 5, and look for the one place it can still go in each box. When you get stuck, try writing small candidate numbers in your head for the squares with the fewest possibilities.