About Sudoku
Sudoku asks for exactly one thing: place the digits 1 through 9 so every row, column, and 3x3 box contains each digit once. No arithmetic, no vocabulary — just pure placement logic, which is why a good grid can quiet a whole noisy afternoon.
Every puzzle here is generated fresh with a single unique solution and rated Easy, Medium, or Hard. Pencil-notes mode keeps candidates tidy, smart highlighting lights up the active row, column, box, and matching digits, and conflicts turn red the moment they appear. You get three hints per game, a mistakes counter, and locally saved best times per difficulty — keyboard or on-screen pad, free in any browser.
How to play Sudoku
- Fill the 9x9 grid so every row, column, and 3x3 box contains the digits 1 through 9 with no repeats.
- Select a cell, then enter a digit with your keyboard or the on-screen number pad.
- Toggle notes mode to pencil in small candidate digits while you reason.
- Watch the highlights — selecting a cell lights its row, column, and box, plus every matching digit on the board.
- Conflicting entries turn red instantly, and the mistakes counter tallies slips.
- Stuck? Spend one of your three hints; complete the grid to stop the clock.
Controls
- Click or tap a cell to select it, then type 1–9 or tap the number pad.
- Toggle notes mode to enter pencil marks instead of full digits.
- Use erase to clear a cell and the hint button (three per game) to fill one correctly.
- Everything works with mouse, keyboard, or touch.
Tips & tricks
- Open by scanning: pick a digit that appears often and work out where it must land in each 3x3 box.
- Hunt naked singles first — cells with only one possible digit — then hidden singles, digits with only one possible cell.
- On Hard grids, keep notes religiously; pairs and triples hiding in your pencil marks are what crack the middle game.
- Save hints for genuine late-game deadlocks — early walls usually yield to a second scan.
Frequently asked questions
Does every Sudoku here have exactly one solution?
Yes. The generator verifies a unique solution for every puzzle at every difficulty, so pure logic is always enough and guessing is never required.
What makes a Sudoku easy or hard?
Mostly the techniques it demands. Easy grids fall to straightforward scanning, while Hard ones expect pencil marks and tactics like pairs and triples to break them open.
How many hints do I get?
Three per game at every difficulty, and each hint fills in one correct digit. The mistakes counter and your best time will both look kinder the less you lean on them.
