A complete beginner's guide — from the basic rules to solving your first puzzle without guessing.
Sudoku is played on a 9×9 grid divided into nine 3×3 boxes. The goal is simple: fill every empty cell so that each row, each column, and each 3×3 box contains the numbers 1 through 9 exactly once. No repeats allowed anywhere.
Before trying anything complex, scan the entire grid for cells that only have one possible number. Look at each empty cell and cross off every number already used in its row, column, and box. If only one number remains — write it in.
This technique is called a Naked Single. In easy puzzles, naked singles alone can solve the entire board.
Pick a number (say, 7) and focus on one row. Find every empty cell in that row where 7 could go. If only one cell can hold 7, place it there — even if that cell has other candidates.
Do this for every number in every row, column, and box. This is called a Hidden Single and unlocks most medium-difficulty puzzles.
For harder puzzles, write small candidate numbers in the corners of each empty cell — every number that could possibly go there. As you fill in other cells, cross candidates off.
When a cell is down to one candidate, fill it in. SudokuSolve has a built-in Pencil Marks mode that does this automatically.
A properly constructed sudoku never requires guessing. If you feel stuck, it means there's a logical technique you haven't applied yet. Try scanning a different row, column, or box, or look for patterns like Naked Pairs and Pointing Pairs. Our Strategy Guide covers all the techniques you need.