Free Sudoku Online. Pure Logic, Zero Distractions.
Play unlimited free Sudoku puzzles online, from easy Sudoku for beginners to expert grids that test your logic. Every puzzle has one unique solution, with pencil notes, hints, undo and autosave built in. No download, no sign-up, no ads between games. New to the game? Learn how to play Sudoku.
An Online Sudoku Game Built for Focus
intosudoku gives you the tools of a serious Sudoku app without the clutter: no pop-ups mid-game, no forced account, no distractions on the grid.
Play Sudoku Instantly
Open the page and start a puzzle in seconds. intosudoku runs in any browser on desktop, tablet and mobile, with no app to install.
Pencil Notes
Switch on notes mode to mark possible candidates in any cell, just like solving with a pencil in a paper puzzle book. Learn how to use notes on hard puzzles.
Unlimited Undo
Take back any move, as many times as you need. Test an idea, and step back if it leads nowhere.
Hints When You're Stuck
Each game gives you three hints. A hint reveals one correct cell, so you get unstuck without spoiling the rest of the puzzle.
Autosave & Resume
Your grid, notes and timer save automatically. Close the tab mid-puzzle and continue exactly where you left off.
Best Times & Streaks
Track your fastest solve, win rate and winning streak for each difficulty on your personal Sudoku stats page.
Sudoku Puzzles for Every Skill Level
Choose easy, medium, hard or expert Sudoku. Every puzzle is generated in your browser and checked to have exactly one solution, so you can always solve it with logic. See which difficulty suits you.
Easy Sudoku
Around 45 given numbers. Ideal for beginners learning the rules.
Medium Sudoku
Around 35 given numbers. A satisfying daily brain workout.
Hard Sudoku
Around 29 given numbers. Pencil notes and careful deduction required.
Expert Sudoku
As few as 23 given numbers. Advanced techniques for experienced solvers.
Start Playing Sudoku in Three Steps
Choose a difficulty
Select Easy, Medium, Hard or Expert and press Start Puzzle. A new Sudoku grid is generated instantly.
Fill in the grid
Select a cell and enter a number, or switch to notes mode to mark candidates. Matching numbers highlight across the board.
Solve or save for later
Finish in one sitting to record your time, or close the tab. Your puzzle is saved and waiting when you return.
How to Play Sudoku
A Sudoku puzzle is a 9×9 grid split into nine 3×3 boxes. Some numbers are given at the start. Fill in the empty cells using the digits 1 to 9 so that three simple rules are always true:
One of each per row
Each horizontal row must contain every digit from 1 to 9 exactly once.
One of each per column
Each vertical column must also contain every digit from 1 to 9 exactly once.
One of each per box
Each 3×3 box must contain every digit from 1 to 9 exactly once. No number can repeat inside a box.
Sudoku Strategies for Beginners
You never need to guess. These techniques will solve every easy and medium puzzle, and most hard ones.
Scan for the obvious
Pick a digit and check every box for it. If rows and columns already block all but one cell in a box, that digit must go there.
Find naked singles
Look at one empty cell and rule out every digit already in its row, column and box. If only one number is left, fill it in.
Find hidden singles
Sometimes a digit fits in only one cell of a row, column or box, even if that cell has other candidates. That cell is the answer.
Use pencil notes
On hard and expert Sudoku, note every candidate in each cell. Patterns become visible that you can't hold in your head.
Spot naked pairs
If two cells in the same unit can only be the same two digits, remove those digits from every other cell in that unit.
Update after every move
Each number you place removes candidates in its row, column and box. Recheck those cells first; new singles often appear there.
Sudoku FAQ
What is Sudoku?
Sudoku is a logic-based number puzzle played on a 9×9 grid divided into nine 3×3 boxes. Some cells start filled in, and your goal is to complete the grid so every row, column and box contains the digits 1 to 9 exactly once. No math is needed, only reasoning. Read the full Sudoku rules.
Is intosudoku really free?
Yes. Every puzzle on intosudoku is free to play, with no sign-up, no subscription and no paywalled difficulty levels.
Which Sudoku difficulty should I start with?
New players should start with Easy, which gives you around 45 starting numbers. Move to Medium once you can finish Easy grids without hints, then try Hard and Expert, which require techniques such as hidden singles and pairs. Read our complete guide on how to play Sudoku to learn these techniques.
Can I play Sudoku on my phone?
Yes. intosudoku works in any modern browser on phones, tablets and computers. There is no app to download. Open the site and start playing.
Will my Sudoku game be saved if I close the tab?
Yes. Your board, pencil notes, timer and mistake count are saved automatically in your browser, so you can resume the puzzle exactly where you left off.
Does every puzzle have a unique solution?
Yes. Every intosudoku puzzle is checked to have exactly one valid solution, so it can always be solved with logic alone. No guessing is required.
Do I need an account to track my Sudoku stats?
No. Your best times, win rate and streaks are saved locally in your browser. You can optionally add a display name on the stats page, but there is no login or password.
Your Next Sudoku Puzzle Is Waiting
Pick a difficulty and start solving free Sudoku online right now. No download, no sign-up.