Sudoku Online – Free Online Puzzle Game

Sudoku Online is a browser version of classic Sudoku, from Smartberry. Fill the nine-by-nine grid so that every row, every column and every three-by-three box contains the digits 1 to 9. No account needed and nothing to download.

Which device? We do not hold a control list for Sudoku Online yet, so we cannot tell you what it expects. Open it and see — and if it does not respond to taps, try it on a computer. The full-screen link above gives it the whole screen either way.

1. The goal is to fill a 9×9 grid with digits from 1 to 9 so that each digit appears exactly once in every row, column, and 3×3 box. Some cells are pre-filled — these are your starting clues.
2. Begin with cells that have the most filled neighbors: fewer options make it easier to identify the correct digit. As cells are filled in, the choices for adjacent ones narrow down — the puzzle unfolds as a chain of logical steps.
3. Use the notes mode to write down multiple candidates in a cell and eliminate them as the grid fills up. This is especially useful at Hard and Expert levels.
4. Additional modes come with extra rules. In X-Sudoku, digits must also be unique along both main diagonals. In Windoku, extra highlighted regions apply the same uniqueness rule. In Killer Sudoku, groups of cells must add up to a given sum. In Kropki, markers between cells define relationships: a white dot means the two digits differ by 1, a black dot means one is exactly twice the other.

Controls — general guide

• Mouse or touch: click, or tap if the game accepts it. Some games here are built for a touch screen and some want a keyboard — the note above says which this one is.
• Keyboard (if the game uses it): arrow keys or WASD to move, and the space bar to jump or act.
• Full screen: use the “Play full screen” button above for a bigger view.

• Read the steps above before your first run — Sudoku Online documents 4 of them, and most early losses are just not knowing the rule.
• Use Play full screen if anything feels cramped — it hands the game the whole window, which matters most on a laptop.
• Nothing saves to SlowDen. Closing the tab ends the run, so finish a level before you leave.