Sudoku

How to play Sudoku

The goal is simple: fill every empty square so that each row, each column, and each of the nine 3×3 boxes contains the digits 1 to 9 exactly once. Every puzzle here has one unique solution and can be solved by logic alone — you never have to guess.

Tap a cell, then tap a number to place it. Turn on Notes to pencil in the candidates for a cell (small numbers), which is how you keep track of the possibilities while you work. Erase clears a cell, Hint fills the selected cell correctly if you're stuck, and cells you fill in wrongly are highlighted so you can spot a mistake early.

Beginner strategy

• Scan for singles. Look for a row, column, or box that already has most of its digits — the missing ones are often forced.
• Hunt one digit at a time. Pick a number, say 5, and see which boxes still need it; often only one cell in a box can take it.
• Use pencil marks. When a cell has only two or three candidates, note them. When a candidate appears in just one cell of a unit, it goes there.
• Work from the most-filled areas outward. The densest rows, columns and boxes give up their answers first and open everything else up.

Easy, medium or hard?

The difficulty is set by how many digits you start with and how much logic each step demands. Easy boards can be solved with simple scanning. Medium boards need pencil marks and a bit of elimination. Hard boards start with fewer givens and require you to chain several deductions together. All three always have exactly one solution.

Why Sudoku is good for your brain

Sudoku is pure logical deduction with no arithmetic at all — the numbers are really just nine symbols. That makes it a focused workout for working memory, pattern recognition and patient, step-by-step reasoning. And because it's absorbing without being stressful, a daily puzzle is a genuinely relaxing way to give your mind a proper stretch.

Frequently asked questions