Sudoku
The classic 9×9 number puzzle. Fill every row, column and 3×3 box with the digits 1–9 — no repeats. Four difficulty levels, pencil notes for tough spots, and a hint button for when you're stuck. Your progress saves automatically in your browser.
- Mobile-friendly
- Keyboard support
- No installs
How to play
The board is a 9×9 grid split into nine 3×3 boxes. Some cells start filled (the "clues"); the rest are empty. Your job is to fill every empty cell with a digit from 1 to 9 so that each row, each column and each 3×3 box contains every digit exactly once.
Click a cell to select it, then click a number from the pad below (or press 1–9 on your keyboard) to fill it in. Use the arrow keys to move the selection. Toggle Notes mode (or pressN) to pencil in candidate digits — small numbers in the corner of a cell that you can later confirm or erase.
Use Hint to reveal the answer for one empty cell, Check to briefly highlight conflicts, and Reset to start the current puzzle over from scratch.
Strategy tips
- Scan each row, column and box for "naked singles" — cells with only one possible candidate.
- Use Notes mode to track candidates in tough cells; eliminate them as peers get filled.
- Look for "hidden singles" — a digit that can only go in one cell within a row/col/box, even if the cell has other candidates.
- Start with Easy puzzles to learn patterns; Expert puzzles often require advanced techniques like X-Wing or naked pairs.
Controls
- Click a cell to select; click a number (or press 1–9) to fill it.
- Arrow keys move the selection. Press N to toggle Notes mode.
- Press Backspace or 0 to clear a cell.
- Switch difficulty from the Easy / Medium / Hard / Expert toggle to start a fresh puzzle.