How the online sudoku game works

When the page loads, the generator builds a complete solution grid and then removes numbers one at a time, re-solving after every removal to prove that only one answer remains. That means every free sudoku puzzle on this page can be finished with pure logic — you never have to guess.

Tap or click any empty square to select it, then use the number pad below the grid or type 1-9 on your keyboard. Arrow keys move the selection, Backspace clears a square, and the counter beside each number shows how many of that digit are still missing.

Tools that make solving easier

• Notes: switch on notes mode to pencil in candidate numbers inside a square, exactly like a paper sudoku.
• Hint: stuck on a hard sudoku? Reveal one correct number and keep going.
• Check: see straight away whether any of the numbers you entered are wrong.
• Highlight conflicts: duplicate numbers in a row, column or box turn red as you type.
• Undo and timer: step back through your moves, and pause the clock whenever you need a break.

Choosing a difficulty

Easy sudoku puzzles leave plenty of starting numbers on the grid and can usually be solved by scanning rows, columns and boxes for the only place a digit can go. Medium puzzles need candidate notes. Hard and expert sudoku puzzles hold back many more clues and reward techniques like naked pairs, hidden singles and pointing pairs.

Prefer a smaller board? Switch the grid size to 4×4 or 6×6 for a quick game, or for younger players who are still learning the rules. The same online sudoku controls work on every grid size.

Online sudoku or printable sudoku?

Playing sudoku online is quick and forgiving — you can undo, check and restart in a second. Printable sudoku is better for classrooms, road trips, waiting rooms and anyone who simply prefers pencil and paper. This site does both, so use whichever suits the moment.

Is this online sudoku game really free?

Yes. You can play as many free sudoku puzzles as you like. There is no download, no account and no paywall — the game runs entirely in your browser.

Do I need to register or install anything to play sudoku online?

No. Open the page and start playing. Nothing is installed and no sign-up is required, so it also works on a school or library computer.

Is my game saved if I close the tab?

Yes. Your current sudoku puzzle, your entries and your time are stored in your own browser, so the same puzzle is waiting when you come back on that device.

How do I play sudoku for beginners?

Fill the grid so every row, column and box contains each number once. Start with easy difficulty, look for rows or boxes that are nearly complete, and read our how to play sudoku guide for step-by-step strategies.

Why do people spell it sodoku, soduku or suduko?

Those are common misspellings of sudoku, a Japanese abbreviation meaning "the digits must be single". However you spell it, the puzzles on this page are the same free sudoku game.