Sudoku
Clear thinking. Clean grid. One satisfying solution.
Time00:00
Mistakes0 / 3
🎉
Clear thinking. Clean grid. One satisfying solution.
Enjoy a clean, free online Sudoku game built for quick daily puzzles and longer solving sessions. Choose your difficulty, use pencil notes, ask for a hint when you need one, undo mistakes, and solve the classic 9×9 Sudoku grid at your own pace.
Sudoku is a logic puzzle played on a 9×9 grid divided into nine 3×3 boxes. Some numbers are already provided as clues. Your job is to fill every empty cell with a digit from 1 through 9.
The rule is simple: each row, each column and each 3×3 box must contain the numbers 1–9 exactly once. You do not need arithmetic. Sudoku is about elimination, patterns and logical deduction.
The key question: which numbers are still possible in this cell after you check its row, column and box?
Good Sudoku solving is not guessing. It is repeatedly narrowing possibilities until a number has only one sensible home.
Look across rows, columns and boxes for places where many digits are already known.
A digit already present in the same row, column or box cannot be used again there.
Pencil in possible numbers when a square is not yet certain, then remove candidates as the puzzle develops.
Keep repeating the process until every row, column and 3×3 box is complete.
Notes are small candidate numbers you can place inside an empty cell when you are not ready to commit to a final answer. If a square might contain 1, 3 or 5, you can mark those possibilities and return to them later.
As other cells are solved, candidates become impossible and can be removed. On harder puzzles, notes make complex deductions easier to see without relying on memory.
Choose a difficulty that fits the moment. Easy puzzles are ideal for learning and quick sessions, while harder levels give experienced solvers more room to reason.
Toggle candidate numbers without committing to a final digit.
Get a helping hand when a puzzle has you stuck.
Step back after a move and reconsider the grid.
Clear a number or candidate marks from a selected cell.
Keep your attention on the selected cell, related row, column and box while you solve.
Track a solving session when you want to, and pause when real life interrupts.
Speed usually comes after pattern recognition. Focus first on making reliable deductions.
Find cells where only one digit can fit after checking the row, column and box.
Use notes on tougher grids so possible values stay visible while you reason.
A 3×3 box often reveals placements that are harder to notice when scanning the entire grid.
Use existing digits in neighboring rows and columns to eliminate squares inside a box.
If two cells in a unit share the same two candidates, those values can often be removed elsewhere in that unit.
When stuck, rescan the puzzle or update your notes before committing to an uncertain digit.
If you have never solved Sudoku before, this is the only idea you need to begin: every empty cell has one correct digit, and the surrounding row, column and 3×3 box tell you what can and cannot go there.
A new puzzle already contains several fixed numbers. These are clues or givens. You do not change them. Their job is to give you enough information to logically determine the missing digits.
For any empty cell, inspect its row, its column, and its 3×3 box. Any digit already present in one of those three units is eliminated from that cell.
Suppose a cell could theoretically contain 1–9, but its row rules out 1, 2, 4 and 8, its column rules out 3 and 7, and its box rules out 5 and 6. Only 9 remains, so 9 belongs in that cell.
Every correct placement changes the puzzle. A digit that looked uncertain a moment ago may become obvious after another cell is solved. Sudoku is a chain of deductions: solve what is clear, then scan again.
Notes are possible answers, not final answers. When Notes mode is on, choosing a number adds or removes that small candidate digit inside the selected empty cell.
Imagine an empty cell could be 1, 3, 5 or 8. Instead of guessing, turn on Notes and record those candidates. As other cells are solved, you can remove candidates that are no longer possible. When only one candidate survives, you have a strong reason to enter it as the final value.
Important: Notes do not change the Sudoku rules. They are simply a scratchpad built into the grid. Turn Notes off when you are ready to enter a normal full-size answer.
Every difficulty uses the same 9×9 board and the same row, column and box rules. The game changes the number of starting clues: fewer clues generally leave more of the grid for you to work out.
A friendly starting point for learning scanning, elimination and basic singles.
The default challenge, with more empty cells and greater value in candidate notes.
More demanding boards where careful rescanning and candidate elimination matter more.
The sparsest option in this game, intended for players who want more cells to deduce.
The controls are there to reduce friction, not solve the puzzle for you unless you explicitly ask for a hint.
Returns the puzzle to the state before your most recent editable action. Use it when you enter, erase or change something and want to reconsider.
Clears the selected editable cell, including its candidate notes. Original clue cells cannot be erased.
Toggles pencil mode. With Notes on, number buttons add or remove small candidates instead of placing a final answer.
Fills the correct value in the selected empty cell. If no empty cell is selected, the game chooses an empty cell for you. The hint counter records each hint used.
Stops the timer and covers the puzzle so you cannot continue solving until you press Resume.
Starts a fresh puzzle at the currently selected difficulty and resets the timer, mistakes, hints, notes and progress for the new board.
On: an incorrect final entry is shown as an error and increases the mistake counter. The display tracks mistakes against a 3-mistake reference, but reaching three does not end your puzzle. Off: entries are not immediately checked against the solution, so you can solve without instant correctness feedback.
On: selecting a cell visually emphasizes related cells in its row, column and 3×3 box, and matching entered numbers can also stand out. Off: the board stays visually quieter while you solve.
Select a cell and use the number keys to enter digits. Keyboard navigation is especially useful for players who prefer a fast desktop workflow.
Arrow keys move the selected cell around the 9×9 grid.
You do not need advanced terminology to enjoy Sudoku, but knowing what to look for makes harder boards much less mysterious.
An empty cell has only one legal candidate after you eliminate digits already used in its row, column and box. That remaining candidate must be the answer.
A row, column or box may have several empty cells, but a particular missing digit can fit in only one of them. That unique location identifies the answer.
If exactly two cells in the same row, column or box are restricted to the same two candidates, those two digits belong to those cells in some order. They can therefore be eliminated from other cells in that unit.
If every possible location for a digit inside one 3×3 box lies on the same row or column, that relationship can eliminate the digit from other cells on that line outside the box.
Checking only the row. A digit must also be legal in the cell's column and 3×3 box.
Treating notes as answers. Candidate marks mean “possible,” not “confirmed.”
Guessing too early. A careful rescan often reveals a deduction you missed and avoids building later reasoning on an uncertain entry.
Forgetting to update candidates. Notes become useful only when you remove possibilities that are no longer legal.
Quick guidance on Sudoku rules, notes, difficulty and online play.
Fill the empty cells so every row, column and 3×3 box contains the digits 1 through 9 without repetition. Use the given clues and logical elimination to determine each missing number.
Notes let you enter small candidate digits inside a cell instead of placing a final answer. They are useful for tracking several possible values while solving harder puzzles.
No. Although Sudoku uses numbers, you do not add, subtract, multiply or divide them. The digits act as symbols in a logic puzzle.
Easy is the natural place to begin. It gives you more immediate deductions so you can become comfortable scanning rows, columns and boxes before moving to harder puzzles.
Rescan areas with many solved cells, update your candidate notes and look for a digit that has only one possible location in a row, column or box. You can also use the game's hint feature when you want assistance.
Yes. The game is designed for responsive browser play, so the grid and controls adapt to desktop and smaller touch screens.
Yes. You can play the browser-based Sudoku game without creating an account before starting.
Yes. Undo lets you step back after a move, while Erase clears the selected entry so you can continue solving.
The 9×9 grid is divided into nine smaller 3×3 boxes. Just like every row and column, each box must contain the digits 1 through 9 without repeating a digit.
No. In a completed standard Sudoku, every row, every column and every 3×3 box contains each digit from 1 to 9 exactly once.
When Mistake Check is on, an incorrect final entry is highlighted and added to the mistake counter. Turning it off removes that immediate correctness check, allowing you to work through the puzzle without instant feedback.
No. The interface shows mistakes against a three-mistake reference and warns you when you reach three, but the current game lets you continue solving.
If you have selected an empty editable cell, Hint fills its correct digit. Otherwise it chooses an empty cell and fills the correct value there. Each use increases the hints-used counter.
Progress shows how many of the board's 81 cells are currently filled, including the original clues. It is a completion indicator, not a score.
Yes. Pause stops the timer and covers the puzzle. Press Resume to reveal the grid and continue from the same position.
In this game, the difficulty choices use different starting clue counts: Easy starts with 44 clues, Medium 36, Hard 30 and Expert 26. The Sudoku rules themselves remain the same.
Play Sudoku online for free with notes, hints, undo, mistake checking and a responsive board designed to keep the puzzle clear and enjoyable.