Sudoku
NEWWorks on both desktop and mobile. Tap or click to play.
About This Game
Play free Sudoku online with Easy, Medium, Hard, and Expert puzzles. Pencil notes, mistake checking, and a timer. No sign-up, works on mobile and desktop.
How to play Sudoku
Objective: Fill all 81 cells so each value matches the puzzle's single hidden solution, which happens exactly when every row, column, and 3x3 box holds the digits 1 through 9 once.
Pick a difficulty first: Easy starts with 40 given digits, Medium 32, Hard 26, and Expert only 23. Fewer givens means fewer footholds, not a bigger grid. Each puzzle is generated fresh and checked to have exactly one solution, so you never guess between two valid answers. Given digits show in gray and are locked. Your own entries appear in cyan. Click a cell to select it, or move the selection with the arrow keys.
Enter a digit by clicking a number-pad button 1 to 9 or pressing that key. Pressing the same digit again clears the cell, and Backspace, Delete, 0, or the Erase button also empties it. A digit that does not match the hidden solution turns red and raises the Mistakes counter, but nothing ends the game, so you can fix it and continue. Duplicate digits sharing a row, column, or box also flash red as conflicts.
Toggle Notes ON to pencil candidates into a cell's mini-grid instead of committing an answer; writing a real digit wipes that cell's notes. Each number-pad button greys out once you place all nine copies of that digit. The timer stays at 0:00 until your first entry, then counts up. You win the instant all 81 cells match the solution, and your fastest time per difficulty is saved locally as your Best.
Tips and strategy
Read the mistake color
A cyan digit turning red means it disagrees with the solution, not just a neighbor. Treat red as proof you are wrong and pull it out at once, since it blocks the cells that depend on that number.
Notes before Expert
On Hard and Expert, with 26 or fewer givens, switch Notes ON and mark candidates for tight cells first. When a box or column narrows a note to one digit, that cell is solved without any guessing.
Chase the greyed buttons
A disabled number-pad button means all nine of that digit are placed. Work the digits with the most missing copies instead, since they have more forced positions across the lines and boxes you have not finished.
Use the value highlight
Select a cell holding a digit and every other copy of that value lights up. Scan for a box or line missing that digit but blocked in all cells but one, which pins its last legal square.
The history of Sudoku
Sudoku's grid descends from the Latin square studied by Leonhard Euler, but the modern puzzle with a partly filled grid and a single solution was designed by Howard Garns, an American architect, and published as Number Place by Dell Magazines in the late 1970s. The publisher Nikoli popularized it in Japan under the shortened name Sudoku, and New Zealander Wayne Gould's puzzle-generating program helped spread it to newspapers worldwide during the mid-2000s boom.
Frequently asked questions
Do mistakes ever end the game?
No. Wrong digits turn red and raise the Mistakes counter, but there is no life limit and no game over. You can make any number of mistakes, correct them, and still finish. The count is only reported in the Solved panel as a record of how clean your solve was.
Can a puzzle have more than one answer?
No. After removing clues the generator counts solutions and refuses any removal that would create a second valid answer, so every puzzle has exactly one solution. Whenever you are stuck, a logically forced move always exists and you never need to guess between two legal possibilities.
When does the timer start, and what is my Best?
It starts on your first entry, not when the puzzle loads, and counts up until all 81 cells match. On a solve, your time replaces the stored Best for that difficulty only if it is faster. Easy, Medium, Hard, and Expert each keep their own record in local storage.
Can I play with the keyboard only?
Yes. Arrow keys move the selected cell, number keys 1 to 9 place digits, and Backspace, Delete, or 0 clears the current cell. Pressing a digit already in the selected cell removes it. To pencil in candidates you still toggle Notes mode from its button.