Free Sudoku Online

Why play here

• No sign-up, no install — it starts in the browser, and there is nothing to dismiss first.
• Three difficulties — easy, medium and hard, with a freshly generated puzzle every game.
• The tools you expect — pencil notes, three hints, undo, and a three-mistake limit.
• Built for phones — large digits and a calm background, comfortable to play one-handed.
• Times kept — your best is stored on your own device, so you can pick the challenge back up.

How to play Sudoku

Fill the 9×9 grid with the digits 1 to 9. There is only one rule: no digit may repeat within a row, a column, or a 3×3 box. Every puzzle has exactly one solution and can be finished by reasoning alone — you never have to guess.

Start with the cells you are certain about. When a cell has several candidates, write them in with the notes tool rather than holding them in your head; that is where most mistakes come from. Three mistakes end the game, so take the extra second.

Four techniques that remove all guessing

Sudoku is never solved by luck. These four carry you through easy and normal, and open the blocked spots on hard.

1. Hidden single — pick one row, column or 3×3 box and count the cells where a 7 could still go. If only one cell qualifies, that cell is a 7, no matter how many other candidates it also holds. This is the workhorse of the opening.
2. Naked single — the same idea turned around. Pick an empty cell and count the digits that could go in it. If only one survives, write it in. Turning notes on makes these jump out at you.
3. Naked pair — when two cells in the same row, column or box hold exactly the same two candidates, those two digits must split between them. So you can erase both digits from every other cell in that unit. It fills nothing directly, but it clears the way.
4. Pointing pair — if every candidate for a 3 inside one box sits in a single row, then the 3 comes from that row. You can therefore erase 3 from the cells of that row that lie outside the box. On hard puzzles this is usually the move that breaks the deadlock.

What the difficulty levels actually change

The three levels differ less in how many digits you start with than in which techniques you need to finish.

• Easy — hidden singles alone will carry you to the end. You never need notes.
• Normal — expect to need naked singles along the way. Notes make it far more comfortable.
• Hard — a naked pair or a pointing pair is required at least once. Scanning by eye will always stall somewhere.

When you feel stuck, stop hunting for a cell to fill and look for a candidate to erase instead. Sudoku rewards subtraction more than addition. And remember three mistakes end the round — if you cannot say in one sentence why a digit belongs there, it is not that cell yet.

Frequently asked questions

Is it really free?

Yes. Every game on the site is free and no account is needed.

Do I need to install an app?

No, it runs in the browser. If you play often, "Add to Home Screen" makes it behave like an app.

Are there other puzzles?

Yes — nonogram, water sort, 2048 and more than thirty other brain games, plus a new daily puzzle.