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By Noyon Rahman · Updated August 2026 · Reviewed for accuracy against the live game
Sudoku is the number-placement puzzle that fills newspapers, airport lounges, and phone screens around the world. A 9x9 grid is divided into nine 3x3 boxes, and your task is to place the digits 1 through 9 so that every row, every column, and every box contains each digit exactly once. There is no arithmetic and no guessing required, only quiet logic. This version offers four difficulty levels from Easy to Expert, plus pencil marks, three hints, and undo, so newcomers can learn the classic solving techniques while veterans get grids that truly bite.
Pick a difficulty and the board fills with starting clues. Click any empty cell and choose a number from the keypad to place it, or switch to pencil mode to jot candidate numbers into the corner of a cell. The golden rule is simple: each row, column, and 3x3 box must hold every digit from 1 to 9 exactly once. Work cell by cell, using the pencil marks to track which numbers are still possible. When a cell has only one candidate left, place it and remove that number from the other cells in the same row, column, and box. If you stall, the hint button highlights a logical next step, and undo lets you back out of a wrong idea. The grid is complete when all 81 cells are filled correctly.
No. The digits are just symbols, so no arithmetic is involved at all. Sudoku tests logic, pattern recognition, and careful observation rather than calculation. You could replace the numbers with letters or shapes and every puzzle would work exactly the same way, which is why it appeals to players of every age.
Pencil marks are the small candidate digits you note in the corner of a cell to remember which numbers could still fit there. They make advanced techniques possible, because you can see at a glance which candidates each cell has already eliminated, and they stop you from retesting numbers you have already ruled out.
Easy boards start with many clues and can be solved with simple scanning of rows and columns. Medium and Hard demand cross-hatching, candidate elimination, and careful pencil marking. Expert puzzles leave the fewest clues, so nearly every placement needs a chain of logical deductions.
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