Every puzzle is built in your browser by the page's own generator, and every one is checked to have exactly one solution. Pencil marks, hints, conflict checking and a timer — no download, no account, no tracking.
Controls: click or tap a cell, then press 1–9 to fill it (or tap the number pad). Arrow keys move the selection, Backspace or 0 erases, and N switches pencil-mark mode on and off.
A Sudoku grid is 81 cells arranged as nine rows, nine columns and nine boxes. The digits are symbols, not numbers: nothing is added up, and 9 is not "greater than" 1 in any meaningful way here. What matters is uniqueness — a digit may appear only once in each of the three kinds of region. The puzzle is solved when all 81 cells are filled and all 27 regions (9 rows + 9 columns + 9 boxes) each contain the digits 1 to 9 exactly once.
This page shows a conflict in red as soon as you place a digit that duplicates one already in its row, column or box, so you can backtrack immediately instead of discovering the problem twenty moves later. Check scans the whole grid and reports how many cells are still wrong; Hint fills in one empty cell from the solution and counts as a hint used.
| Level | Given digits | What it asks of you |
|---|---|---|
| Easy | ~45 | Plain scanning: most cells can be solved by elimination alone. |
| Medium | ~36 | Needs pencil marks and single-candidate searching in places. |
| Hard | ~28 | Requires paired candidates and careful cross-hatching across boxes. |
All three levels are produced by the same generator and all three are verified to have a unique solution before they are shown to you — the difference is only how much information is left on the board.
Most online Sudoku sites download a puzzle from an API, then upload your progress, your time and your mistakes to a leaderboard. Here the generator is a few dozen lines of JavaScript running in your tab: it builds a complete solution grid, digs cells out of it at random, and after each removal re-solves the puzzle to make sure the answer is still unique. Only when that check passes is the puzzle handed to you.
Nothing about your game leaves the device. The timer, the mistake count and your best time per difficulty are held in memory and in your browser's own local storage. Load the page, then disconnect your network — the puzzle keeps working, because there is nothing left to load. Advertising on this site is served by Google AdSense in separate ad frames that never see the board, and rejecting advertising cookies has no effect on the game.
Yes. After each cell is removed, the page re-solves the puzzle and counts solutions; if more than one exists, that cell is put back. This is why generating a hard puzzle takes a moment longer than an easy one.
It is possible but very unlikely — the generator fills the solution grid in random order, so the number of possible boards is astronomically large.
It fills one cell from the solution and increments your hint counter, so you can see how much help you used. It never reveals the whole grid.
In your browser's local storage, per difficulty level. Clearing site data resets it; there is no account and no server copy.
Yes. Tap a cell then tap a number on the pad. The board scales to the screen width and needs no keyboard.