Sudoku

Sudoku is a number puzzle played on a 9×9 grid that is split into nine 3×3 boxes. Some cells start with digits already in place. Your job is to fill every empty cell so that each row, each column and each box contains the digits 1 to 9 exactly once. No maths is involved: the digits are just nine different symbols, and every puzzle here has one solution that you can reach by logic alone, without guessing.

How to play

• Tap a cell to select it, then tap a number on the pad. On a keyboard, type 1–9 and move with the arrow keys.
• Turn on Notes (or press N) to pencil in the digits a cell might be. Placing a digit clears it from the notes around it.
• A wrong digit turns red and counts as a mistake. Prefer to find your own errors? Turn off Show mistakes as I play in the menu and the board is only checked once it is full. Switch on the 3-mistake limit if you want a challenge.
• Undo as often as you like. Each puzzle comes with two free hints, and a hint tells you why the digit goes there. A hint never gets spent on a digit that is already red: it just points you to it so you can erase it.
• The number under each key shows how many of that digit are still to place.

Beginner techniques

Scan a box. Pick a digit, say 7, and a box that has no 7 yet. Look along the rows and columns that cross the box: every 7 already on them rules out cells in the box. If only one cell is left, the 7 goes there. Easy puzzles can be solved with this move alone.

Scan a row or column. The same idea works along a line: if a digit has only one possible cell in a row or column, place it.

Last digit in a cell. Sometimes a cell sees eight different digits in its row, column and box. The ninth digit is the only one that fits. Medium puzzles need both kinds of single.

Pairs and pointing. On Hard puzzles, use notes. If two cells in a row can only be 3 or 8, those two digits belong to those cells, so cross 3 and 8 off the rest of the row. If the only spots for a digit inside a box lie on one line, that digit can be removed from the rest of that line. Expert puzzles go further, with triples, X-wings and wing patterns.

The daily puzzle

Every day there is one new Daily Sudoku, the same for every player. It is Medium on weekdays and Hard at the weekend, and a fresh one arrives at midnight your local time. Solve it on consecutive days to build a streak, then share your time and mistakes with friends. If you start a daily just before midnight you can still finish it after, and it counts for its own day. Your progress, best times and streak are saved in this browser, so you can close the tab and pick up where you left off.