Play Sudoku Online Free — One Grid, One Solution

Why “exactly one solution” matters

Plenty of free Sudoku sites serve puzzles with two, three or more valid solutions — and then mark your perfectly logical answer wrong. Every puzzle here is generated fresh in your browser and checked by a built-in counting solver: if it does not have exactly one solution, it never reaches your screen. That means logic alone, from the first clue to the last digit, always carries you to the finish — no guessing required.

• Four difficulty levels — Easy, Medium, Hard and Expert; more givens removed, tougher techniques needed.
• Smart hint — stuck? The hint fills the selected cell (or picks one) with the correct digit.
• Pencil marks — jot candidate numbers in the corners of any cell, toggle with one tap or the N key.
• Undo & erase — experiment freely; every step can be taken back.
• Timer & best records — chase your personal best for each level, saved on your device.

How to play Sudoku in sixty seconds

Fill the 9×9 grid so that every row, every column and every 3×3 box contains the digits 1–9 exactly once. The pre-filled digits (givens) are your anchors: scan for rows, columns or boxes that are missing only one or two digits, place what is forced, and repeat. When scanning stalls, pencil-mark the candidates and look for a digit that fits only one cell in a box — that is a “naked single”, the bread and butter of Sudoku solving.

Tap a cell and tap a number on the keypad, or use your keyboard: digits to fill, arrow keys to move, Backspace to clear, N to toggle notes.

Three habits that unlock Hard and Expert

1. Finish every scan before you guess. Hard puzzles rarely give up a digit to a single technique; they give it up after two or three techniques have run in sequence. 2. Watch pairs and triples. When two cells in a box can only be {4,7}, those digits are locked there — erase them from every other cell in that box and new singles appear. 3. Keep pencil marks honest. Stale notes hide real candidates; erase a note the moment its digit is disproven, and the Expert grid will slowly disassemble itself.

And when a grid truly wins the standoff — the hint button reveals one correct digit at a time, so you can keep solving with dignity intact.

Frequently asked questions

Is Sudoku free to play here?

Yes — unlimited puzzles at all four levels, free, with no ads interruption, no download and no account.

Are the puzzles always solvable by logic alone?

Yes. Every puzzle is verified to have exactly one solution, so pure logic always reaches the finish without guessing.

What does the hint do?

It fills your selected empty cell — or picks one for you — with the correct digit. One digit at a time, never the whole grid.

Can I play on my phone?

Yes. The board, keypad and notes are touch-optimised and adapt to any screen size, portrait or landscape.