Every 9x9 puzzle is generated instantly with a guaranteed unique solution — solve one and the next loads automatically, climbing from Easy to Expert.
Score: 0EasyPuzzle #1⏱ 00:00
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What is Sudoku?
Sudoku is a number-placement puzzle that traces back to Switzerland but became a worldwide phenomenon after a Japanese publisher popularized it in the 1980s. A 9x9 grid is split into nine 3x3 boxes, and the goal is to fill in the empty cells with digits 1-9 so that no number repeats in any row, column, or box. Every puzzle in this version is generated on the fly rather than pulled from a fixed set, so in theory you'll never run out.
Difficulty keeps climbing
Finish a puzzle and the next one loads automatically, with difficulty stepping up from Easy to Medium to Hard and finally Expert, then staying at Expert from there on. Difficulty is mainly tuned by how many starting clues are kept — fewer clues generally means more logical deduction is needed to make progress. It's designed as a clear, escalating curve while still guaranteeing every puzzle is solvable.
How to play
Tap a cell to select it, then press 1-9 on your keyboard (or use the on-screen number pad) to fill it in; Backspace, Delete, or the pad's Clear button empties the cell. Gray-background digits are the puzzle's given clues and can't be changed — white cells are the ones you fill in. If a digit you enter conflicts with another in the same row, column, or box, it turns red as a warning, but nothing blocks the input — you can decide whether to fix it or move on. Fill in every cell correctly and the puzzle is automatically marked complete, then the next one loads.
Hints and starting over
Stuck? Tap Hint and the game will correctly fill in one cell for you (at the cost of some points, and it's marked in a different color so you can tell it was a hint). Clear My Entries wipes everything you've filled in yourself while keeping the puzzle's original clues intact, so you can start reasoning through it again from scratch.
Frequently Asked Questions
What are the rules of Sudoku?
The 9x9 grid is split into nine 3x3 boxes. The goal is to fill in digits 1-9 so that every row (9 cells across), every column (9 cells down), and every 3x3 box contains each number exactly once, with no repeats.
Is every Sudoku puzzle guaranteed to be solvable?
Yes, and the solution is guaranteed unique. Puzzles in this version are generated by first building a complete solution, then removing digits to create clues; a solving algorithm checks along the way that the remaining clues still map to exactly one solution before the puzzle is finalized, so you'll never hit an unsolvable or ambiguous puzzle.
How is difficulty ranked?
Difficulty is mainly ranked by how many starting clues (given numbers) remain on the board — more clues is generally easier, and fewer clues generally requires more complex deduction. It's a simplified estimate rather than a full solving-technique classification (it doesn't specifically distinguish puzzles that require advanced tricks like an XY-Wing, for example), but it's enough to produce a clear, gradual curve from Easy to Expert.
Does the difficulty keep getting harder forever?
Yes. After you finish the first (Easy) puzzle, the next one loads automatically, stepping up Easy → Medium → Hard → Expert, then staying at Expert from then on — it won't keep dropping the clue count past the point where puzzles could become unstable, so the curve keeps climbing while every puzzle stays reliably solvable.
What does the Hint button do?
Tapping Hint automatically fills in one correct cell for you, at the cost of some points. That cell is then marked in a different color so you can tell it apart from the digits you entered yourself.