SUDOKU
SUDOKU is a free web game where you play sudoku online with a pencil: fill the grid so every row, every column and every 3x3 box holds the numbers 1 to 9 exactly once. It runs in your browser with no download.
A sudoku cut out of a newspaper is taped into a graph paper notebook. Tap a cell and it gets a yellow highlighter stroke; tap a number card below and the number is written in pencil with a scratch of lead. Every copy of the number you picked shows up in a lighter highlight, and when you finish a row, a column or a 3x3 box a green highlighter sweeps across it.
Turn on MEMO to pencil small candidate numbers into a cell. When you write a number, it is removed from the notes in the same row, column and box automatically. The eraser leaves a little puff of eraser crumbs, and undo takes back one move at a time. Write a number that already sits in the same row, column or box and both get a red pencil circle. Mistakes are unlimited, there are no lives to lose, and there is no hint button that gives away the answer.
There are 60 puzzles: 12 Beginner puzzles starting with 50 clues, then 12 Easy, 12 Medium, 10 Hard, 8 Expert and 6 Master, with fewer clues and harder logic as you go. The first puzzle of every level is open from the start, and inside a level you unlock the next puzzle by solving the one before it. Each solved puzzle gets a red GREAT JOB stamp, and solving all 60 ends the game with a gold one.
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- Type
- Puzzle game · Sudoku game · Indie game
- Built in
- 1 day
- Tech
- Canvas 2D · puzzle generator graded by solving technique (Python) · Web Audio
- Players
- 1
- Plays on
- Phone · PC
- Status
- Finished · 60 puzzles · 6 levels from Beginner to Master
- Released
- 2026-10-05
- Last update
- 2026-10-05
Good for — anyone learning sudoku who wants easy puzzles first, anyone who likes pencil notes but would rather play on a phone than on paper, and anyone who wants to beat Master.
Frequently asked questions
What are the rules of sudoku?
Fill the empty cells so that each of the nine rows, the nine columns and the nine 3x3 boxes contains the numbers 1 to 9 exactly once. The printed numbers cannot be changed, and every puzzle has exactly one solution.
Where should a beginner start?
Start at Beginner 1. Beginner and Easy puzzles can be solved all the way by finding cells that have only one possible number. From Medium on you will need to pencil in candidates and compare them.
Is there a mistake limit?
No. Mistakes are unlimited. If you write a number that already appears in the same row, column or 3x3 box, both numbers get a red circle and a short sound plays, but nothing is taken away. A number that breaks no rule but is not the answer is not marked, so you will get stuck somewhere later.
How do pencil notes work?
Switch MEMO to ON and tap number cards to write small candidates in the cell; tap again to remove one. Writing a real number clears that number from the notes in the same row, column and box. On PC, the N key turns notes on and off.
Can I go straight to the hard puzzles?
Yes. The first puzzle of every level is unlocked from the start. Tap the level name on the title screen to open the table of all 60 puzzles; inside a level you unlock the next puzzle by solving the one before it. Solved puzzles get a red circle.
How hard is Master?
The six Master puzzles have 24 to 26 clues and were picked because named techniques such as pairs and X-wing are not enough to finish them. Every puzzle was checked by a solving program when it was made.
