Sudoku

How to use it

• Play — a puzzle at the chosen level, one you have not played yet. Choosing another level starts a game at it.
• Daily — one puzzle per date, the same for everyone, numbered from 18 October 2026. It gets harder through the week: Monday Easy, Tuesday Medium, Wednesday Hard, Thursday Expert, Friday Master, Saturday Extreme, Sunday Medium.
• Your puzzle — type the givens onto an empty grid, or paste 81 characters, row by row, with 0 or . for an empty cell (spaces and line breaks are ignored). Each digit moves on to the next cell, so a puzzle can be typed straight through. It is checked for exactly one solution before it is played, and graded like the others.

Select a cell, then a digit on the pad or the keyboard. The arrow keys move around the board, Backspace, Delete or 0 clears a cell, N switches notes on and off, and Shift with a digit adds a note. Ctrl+Z undoes and Ctrl+Y redoes. A digit fades on the pad once all nine are on the grid.

Notes are pencil marks. Placing a digit clears it from the notes of its row, column and box, and Undo brings them back. A digit that repeats in a row, column or box shows in red; it is allowed, so you can try an idea and undo it. There is no mistake limit.

Hint first points out a digit that is wrong. Otherwise it finds the simplest next step from your correct digits, highlights the cells it rests on and explains it; the second press applies it. A step that rules digits out writes them into the notes of the cells it touches, struck through first, so it shows even if you keep no notes. Where no technique finds a step, Hint offers to reveal a cell.

The timer starts with the first move and stops while the tab is hidden or the game is paused; pausing hides the grid. Stats are kept per level: games played, wins, current and best streak, best and average time. A game finished with a revealed cell counts as played, not won, and so does one left for a new game after its first move. Hints and undo are allowed in a win, and the result and the shared text list them.

Print puzzles prints 1, 2, 4 or 6 puzzles a page, up to five pages, on A4 or Letter, with their solutions on a last page. Each is labelled with its level and number.

How the puzzles are made and graded

Each row, column and 3 × 3 box holds the digits 1 to 9 once. The boxes are numbered 1 to 9 from the top left, row by row, and a cell is named by row then column: r4c7 is row 4, column 7.

The puzzles come from a fixed bank of 2,000 per level, made in advance. A solved grid is drawn at random, and its digits are taken away one by one, each removal kept only while the puzzle still has exactly one solution and can still be solved within its level. Easy to Expert puzzles keep 180° rotational symmetry. A puzzle's number is fixed, so a shared link always opens the same one.

Grading solves a puzzle the way a person does: it takes the simplest step any technique finds, applies it, and starts again from the simplest. The level is the hardest technique that path needs, so a puzzle always gets the same grade, and Hint follows the same path from wherever you are. A puzzle that needs more than these techniques is “Beyond Extreme”; for it, Hint offers to reveal a cell where no step is found.

Worked hints

Levels and techniques

Frequently asked questions

See also

• Sudoku Solver — to solve any puzzle at once or step by step, or check your digits on one from paper.
• Minesweeper — for a logic puzzle against the clock, with no-guess boards.