Sudoku Classic Legacy Puzzle
The classic 9×9, done properly. Every grid is generated fresh and checked to have exactly one solution, so you never have to guess. Pencil marks, hints, unlimited undo and a clock that stops when you pause.
Plays in the browser. Your game is saved on your own device, not on a server.
Select a square and its row, column and box light up — and so does every other square holding the same digit.
Four grades, honestly rated
Difficulty is not guessed from how many clues are left. Every generated puzzle is solved by the same technique ladder a person would use, and graded by the hardest technique it actually needs.
Everything the grid asks for
The tools a real Sudoku player expects, and nothing that gets in the way of the puzzle.
Pencil marks
Jot candidates into a square exactly as you would on paper, then commit when you have narrowed it to one. Writing a digit clears it from the notes around it.
Unlimited undo
Walk back as far as you like. A mistyped digit costs you nothing but the keystroke it takes to take it back.
Hints, rationed
A hint allowance that shrinks as the grade rises — enough to unstick you, never enough to solve the grid for you.
A clock that pauses
The timer stops the moment you do, and your best time is kept separately for each grade.
Keyboard or touch
Arrow keys move, 1–9 write, N toggles notes, H takes a hint and Ctrl+Z undoes. On a phone, everything is under your thumb.
Continue, always
Progress is written after every move, in your own browser. Close the tab mid-puzzle and it is waiting when you come back.
One puzzle a day, the same one for everyone
The Daily Challenge is seeded from the calendar date, so the grid you get on a given day is the grid everyone else gets. Solve it and your streak grows; skip a day and it starts again.
The grade rises with your own history, not the calendar — five easy dailies, then ten medium, then fifteen hard, then expert. Nobody is dropped into an expert grid on day one.
On your phone as well
The same game, the same engine, the same puzzles — built for Android and iOS, fully offline, in nineteen languages.
The mobile builds are not on the stores yet. When they are, the links will be here; there is nothing to sign up for in the meantime, and the browser version is the whole game.
Common questions
Is it really free?
Yes. There is no account, no paywall and nothing to unlock. The browser version shows no advertising at all; the mobile builds carry a single banner, which is described in the privacy policy.
Does every puzzle have exactly one solution?
Every one. The generator digs clues out of a solved grid and re-checks uniqueness after each removal; a puzzle that would have two solutions is never produced. That is what makes guessing unnecessary — there is always a next square you can prove.
Where is my progress saved?
In your own browser, on your own device. The board, the notes, the clock, your statistics and your settings are written locally after every move. Nothing is uploaded, and clearing your browser's site data erases all of it.
Can I play without a mouse?
Yes. Arrow keys move the selection, 1–9 write a digit, Backspace clears a square, N toggles notes, H takes a hint, Ctrl+Z (Cmd+Z) undoes and Esc pauses.
What happens if I make a mistake?
A wrong digit stays on the board in red and costs one of your three tries. Run out and the run ends — but the puzzle is still there to restart, with the same clues.