Sudoku, originating in 18th-century Switzerland, is a logic-based number puzzle played on a 9x9 grid.
The goal is to fill in the empty cells with digits from 1 to 9 so that each row, column, and 3x3 subgrid
contains all of the digits from 1 to 9 without repetition.
This Sudoku Generator provides free online puzzles across six difficulty levels. Generate
unlimited random Sudoku puzzles and even print them to enjoy offline.
Sudoku is played on a 9x9 grid, which is further divided into nine 3x3 blocks. The goal is to fill every cell with a number from 1 to 9, so that each row, column, and 3x3 block contains all the digits from 1 to 9 without repetition. Some cells will already be filled in at the start of the game. These are your clues. Use logic and deduction to determine the correct numbers for the remaining empty cells.
Scanning: Scan rows, columns, and 3x3 blocks to see which numbers are already present and which are missing. This helps you narrow down the possibilities for empty cells.
Single Candidate: If an empty cell can only contain one possible number (because all other digits are already present in the same row, column, or 3x3 block), then that number must be the solution for that cell.
Hidden Singles: Sometimes a number can only go in one specific cell within a row, column, or 3x3 block, even if that cell could theoretically contain other numbers as well. Look for these "hidden singles" to make progress.
Elimination: As you fill in numbers, keep eliminating possibilities for other cells. This can often lead to finding single candidates or hidden singles.
Trial and Error (Pencil Marks): For more difficult puzzles, it can be helpful to use pencil marks to jot down possible candidates in each cell. This allows you to experiment and backtrack if necessary. (This feature is not currently supported on this website.)