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Sudoku

Sudoku is part of Toolspire and is ready as soon as this page loads. Classic 9×9 Sudoku in four levels, from easy to expert — with pencil notes, undo, hints that explain the next logical step, a new daily puzzle, printable puzzle sheets and a solver for puzzles from the newspaper.

Runs in this tabFreeNo account

On this page

What you can do here

Always solvable by logic

One solution and no guessing — each puzzle is checked by a solver that thinks like a person.

Hints that teach

See the technique behind each hint, from hidden singles to X-Wings.

Pencil notes

Jot candidates by hand, fill them in automatically, and they tidy themselves as you place digits.

Daily puzzle

A fresh medium puzzle every day — the same for everyone — and a streak to keep up.

Print and play

Make a PDF of new puzzles with answers for travel, classrooms or the newspaper habit.

Your game is kept

Close the tab and carry on later; the game is saved in this browser.

The sequence

How to play Sudoku

  1. 1

    Know the rule

    Fill every row, every column and every 3×3 box with the digits 1 to 9, each exactly once.

  2. 2

    Pick a cell

    Tap a cell (or use the arrow keys) and tap a number — or type it.

  3. 3

    Use notes

    Switch on Notes to pencil in the digits a cell could be, or press Auto notes.

  4. 4

    Get unstuck

    Press Hint to see the next logical step and why it works.

Worth knowing

  • Sudoku on Toolspire: four levels — Easy, Medium, Hard and Expert — graded by the techniques a person needs, from simple singles to pairs, pointing pairs, X-Wing and XY-Wing.
  • Every puzzle is newly made, has exactly one solution and can be solved by logic alone, without guessing.
  • Hints explain the next step — which digit goes where and why — and point out a wrong digit first if you have one.
  • Pencil notes, automatic notes, undo, mistake highlighting, a timer with pause, and your best time for each level.
  • A new daily puzzle that is the same for everyone, with a streak counter.
  • Print 1 to 48 puzzles as a PDF (1, 2, 4 or 6 a page, A4 or US Letter) with answer pages, or solve a puzzle from a newspaper or app.

Sudoku techniques, from easy to expert

TechniqueLevelWhat it means
Naked singleEasyA cell where only one digit is still possible.
Hidden singleEasyA digit that fits in only one cell of a row, column or box.
Pointing pair / box-lineHardA digit locked into one line of a box (or one box of a line) can be removed elsewhere.
Naked / hidden pair and tripleHardTwo or three cells that share the same two or three digits rule those digits out of the rest of the unit.
X-WingExpertA digit limited to the same two columns in two rows can be removed from the rest of those columns.
XY-WingExpertThree two-digit cells that force a digit out of any cell that sees both ends.

FAQ

Questions about Sudoku

Where does Sudoku run?

Sudoku runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

Is this Sudoku free?

Yes — unlimited puzzles, hints, the daily puzzle and printable PDFs, with no account.

Does every puzzle have one solution?

Yes. Each puzzle is checked by a solver to have exactly one solution, and a second, human-style solver makes sure it can be finished by logic alone.

What makes a Sudoku hard?

Not the number of clues but the techniques needed. Easy and medium puzzles need only singles; hard ones need pairs or pointing pairs; expert ones need an X-Wing or XY-Wing.

Can I solve a Sudoku from the newspaper?

Yes. Open Solve my puzzle, type or paste the clues, and see the solution, whether it has exactly one solution and how hard it is — or play it here with hints.

Is my game saved?

Yes, in this browser: the game in progress, your settings and your best times. Nothing is uploaded.

Keep going

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