How to play Sudoku
Sudoku is a number-placement logic puzzle. Fill the 9 × 9 grid so that every row, every column and every 3 × 3 box contains each digit from 1 to 9 exactly once.
Every puzzle is freshly generated, has exactly one solution and can be solved with logic alone.
Rules
- Choose Easy, Medium, Hard or Expert. Harder puzzles give fewer starting clues and need more advanced techniques.
- Digits that clash with another in the same row, column or box are highlighted.
- Use pencil notes to track candidates. Turn on Auto notes to fill in every candidate and keep them updated as you play; turn it off to clear all notes.
- A hint fills in one correct digit, but solves that used hints don’t count towards your best time.
- Your progress is saved separately for each difficulty, so you can switch and come back later.
Controls
- Click / tap a cell
- Select it, then pick a number on the pad
- 1–9
- Place a digit (Shift + digit adds a note)
- Arrows / WASD
- Move the selection
- N
- Toggle notes mode
- M
- Toggle auto notes (off clears all notes)
- Backspace / 0
- Erase
- Z / Ctrl+Z
- Undo
- H
- Hint
- P
- Pause
Tips
- Start with “naked singles”: cells where only one digit can fit.
- Then look for “hidden singles”: a digit that has only one possible place in a row, column or box.
- On Hard and Expert, use notes to spot pairs: two cells in a group that share the same two candidates rule those digits out everywhere else in the group.
About Sudoku
Sudoku’s modern form first appeared as Number Place in Dell Pencil Puzzles and Word Games in 1979, designed by Howard Garns, a retired architect from Indiana. Japanese publisher Nikoli picked it up in 1984, gave it the name Sudoku and its symmetrical clue layout, and a 2004 run in The Times turned it into a worldwide habit. It looks exactly like work, which has served it well in offices.
Every puzzle here is generated fresh with a single solution and graded by the techniques it needs. We added pencil notes, auto-notes, hints, undo and a saved game for each difficulty.
Questions
Is every Sudoku solvable without guessing?
Every puzzle has exactly one solution. Easy, Medium and Hard are graded so that singles, locked candidates and naked pairs are enough to finish them. Expert puzzles can need advanced techniques such as chains, so bring the pencil notes.
How do I enter pencil notes?
Press N to toggle notes mode, or hold Shift while typing a digit. Auto notes (M) fills in every candidate and keeps them updated as you play; switching it off clears all notes.
Do hints affect my time?
Yes. A hint fills in one correct digit, but a puzzle solved with hints does not count towards your best time for that difficulty.
Is my puzzle saved if I leave?
Yes. Progress is saved locally and separately for each difficulty, so you can keep an Easy and an Expert on the go and pick either up later.