Sudoku

About This Sudoku

Every board on this page is generated fresh in your browser when you press New Puzzle. The generator first builds a complete valid grid, then removes cells one at a time — after each removal it counts how many solutions remain and puts the digit back if the puzzle would become ambiguous. That is why you never get a board with two possible answers, which is the most common complaint about auto-generated Sudoku on other sites.

Getting Unstuck

Start by scanning for naked singles: a cell where eight of the nine digits are already visible in its row, column or box. Work through all of them, then look for hidden singles — a box where a given digit can only land in one remaining cell. Those two techniques alone solve most easy and medium boards. On hard boards, move to pencil-mark style elimination: pick a digit, mark every cell where it could still go, and look for rows or boxes where it is forced into a single position.

Times and mistakes are stored in your browser only. Nothing about your play is uploaded anywhere.