Quick Rules
Sudoku is a number puzzle for one person. There is no arithmetic in it at all. The numbers are only nine different marks, and the puzzle is about where each one fits.
- The grid has 9 rows, 9 columns and 9 boxes of nine squares, marked off by thick lines.
- Fill every empty square with a number from 1 to 9.
- Each row must hold 1 to 9, with no number twice.
- Each column must hold 1 to 9, with no number twice.
- Each box must hold 1 to 9, with no number twice.
- The bold numbers were printed with the puzzle and never change. You fill in the rest.
To play here, tap an empty square and then tap a number. If you would rather fill in all the 5s at once, tap the number first and then each square where it goes.
Three Levels, and Never a Guess
Every puzzle here has exactly one solution and can be finished by reasoning alone. The level tells you what kind of reasoning it takes.
- Easy: one square at a time. Look for the only place a number can go, and you will get there.
- Medium: now and then you need a pair of squares, or a number pinned to one line of a box.
- Hard: notes and patience. The patterns reach across several rows or columns.
Stuck? Hint marks a square you can fill and tells you why in a sentence, such as "this is the only place for a 7 in this row." It always uses the simplest reason available, so the hints teach you the method as you go.
Tips for Getting Started
- Start with the number you see most. The number pad shows how many of each are still missing. A number with only two or three left is quick to finish.
- Work one box at a time. Pick a number and ask where it can go in a box. Rows and columns that already hold that number rule squares out.
- Check the nearly full lines. A row, column or box with one or two gaps almost fills itself.
- Use notes when two squares are both possible. Small notes save you from holding it all in your head.
- Never guess. If you are not sure, look somewhere else. There is always a square that can be proved.
Frequently Asked Questions
Is this Sudoku free?
Yes. You can play as many puzzles as you like for free, with no account, no download and no pop-up ads.
Does every puzzle have exactly one solution?
Yes. Each puzzle is built in your browser from its puzzle number and checked before you see it. There is always one way to fill the grid and never two, so you are never left with a coin toss at the end.
Do I ever have to guess?
No. Before a puzzle is shown, a solver works through it using only step-by-step reasoning, the same kind you would use with a pencil. A puzzle that would need a guess is thrown away. That is true for Hard puzzles too.
What is the difference between Easy, Medium and Hard?
The levels are set by the kind of thinking a puzzle needs, not only by how many numbers are printed. Easy puzzles can be finished by finding one square at a time. Medium puzzles sometimes need you to notice a pair of squares, or a number that is pinned to one line of a box. Hard puzzles need small notes and patterns that reach across several rows or columns.
How do notes work?
Tap Notes to turn it on, then tap numbers to write small reminders in a square. They are for numbers you think could go there. Tap Notes again to go back to writing real numbers. When you place a number, the matching notes in its row, column and box are rubbed out for you.
Can I turn off the marks for wrong numbers?
Yes. Open Settings and untick the box that says Tell me right away when a number is wrong. The marks start switched on for Easy puzzles and switched off for Medium and Hard. With the marks off, Hint will still point out a wrong number if you ask.
Is there a timer?
Only if you want one. The timer is hidden to begin with, because many people enjoy the puzzle more without a clock. You can show it in Settings. There is no time limit either way.
Does the game save my progress?
Yes. Your puzzle is saved in your browser after every number and every note, so you can close the page and carry on later on the same device.
What is the Daily Puzzle?
Each day has its own puzzle number, taken from the date, with one puzzle for each level. Everyone who plays that day gets the same grid, so you can compare notes with a friend or a spouse. You can also share any puzzle by its number: type the number in Settings.
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